Kurzgesagt – In a Nutshell
Kurzgesagt – In a Nutshell
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Sources – Superpredators
Sources – Superpredators
We thank the following experts for their critical reading, feedback and corrections:
– Prof. Kenneth Dumack
University of Koblenz, Germany
– Prof. Edward Mitchell
University of Neuchâtel, Switzerland
– Prof. Agnieszka Pajdak-Stós
Jagiellonian University, Kraków, Poland
– In a single drop of seawater there are about a million microbes and ten million viruses.
Microscopic lifeforms (outside of viruses) include bacteria, archaea, and very small (micro-)eukaryotes such as e.g. protists. Bacteria, archaea, and microeukaryotes are often grouped under the label “microbes”, which we do here as well.
The below figure shows microbial and viral abundance (in cells per mL) in seawater at different depths. Microeukaryotes are included in “microbes”.
#Wigington, C., Sonderegger, D., Brussaard, C. et al. Re-examination of the relationship between marine virus and microbial cell abundances. Nat Microbiol 1, 15024 (2016).
– Here we find our superpredators hunting their prey. Extremely weird creatures. Protists, the first complex life forms with a nucleus that evolved about two billion years ago. They are the ancestors of all animals, plants and fungi.
“Protists” are all eukaryotes that are not land plants, animals or fungi – they are defined by exclusion. All eukaryotes share a common ancestor that lived over 1.5 billion years ago. Early descendants of this ancestor looked like what we now call protists (mostly single-celled, simple eukaryotes). Plants, animals, and fungi evolved later from different protist lineages, not from one another. And the protists we know today have evolved as long as animals, plants and fungi. In a nutshell, protists are therefore the earliest branches of the eukaryotic family tree and from them, all other major eukaryotic lineages evolved. This is what we mean by protists being the “ancestors” of animals, plants and fungi.
Protists are a diverse group that includes predators and grazers like we describe in this video, but also photosynthetic protists (algae), amoebae, etc.
#Schoenle A, Francis O, Archibald JM, et al. Protist genomics: key to understanding eukaryotic evolution. Trends Genet. 2025 https://www.sciencedirect.com/science/article/pii/S0168952525001118
Quote: “All eukaryotes other than animals, plants, and fungi are protists. Protists are highly diverse and found in nearly all environments, with key roles in planetary health and biogeochemical cycles. They represent the majority of eukaryotic diversity, making them essential for understanding eukaryotic evolution.”
#Knoll AH. Paleobiological perspectives on early eukaryotic evolution. Cold Spring Harb Perspect Biol. 2014
https://pmc.ncbi.nlm.nih.gov/articles/PMC3941219/
Quote: “Eukaryotic organisms radiated in Proterozoic oceans with oxygenated surface waters, but, commonly, anoxia at depth. Exceptionally preserved fossils of red algae favor crown group emergence more than 1200 million years ago, but older (up to 1600–1800 million years) microfossils could record stem group eukaryotes. Major eukaryotic diversification ∼800 million years ago is documented by the increase in the taxonomic richness of complex, organic-walled microfossils, including simple coenocytic and multicellular forms, as well as widespread tests comparable to those of extant testate amoebae and simple foraminiferans and diverse scales comparable to organic and siliceous scales formed today by protists in several clades. Mid-Neoproterozoic establishment or expansion of eukaryophagy provides a possible mechanism for accelerating eukaryotic diversification long after the origin of the domain. Protists continued to diversify along with animals in the more pervasively oxygenated oceans of the Phanerozoic Eon.”
#A.H Knoll, E.J Javaux, D Hewitt, P Cohen; Eukaryotic organisms in Proterozoic oceans. Philos Trans R Soc Lond B Biol Sci (2006)
https://doi.org/10.1098/rstb.2006.1843
Quote: “The geological record of protists begins well before the Ediacaran and Cambrian diversification of animals, but the antiquity of that history, its reliability as a chronicle of evolution and the causal inferences that can be drawn from it remain subjects of debate. Well-preserved protists are known from a relatively small number of Proterozoic formations, but taphonomic considerations suggest that they capture at least broad aspects of early eukaryotic evolution. A modest diversity of problematic, possibly stem group protists occurs in ca 1800–1300 Myr old rocks. 1300–720 Myr fossils document the divergence of major eukaryotic clades, but only with the Ediacaran–Cambrian radiation of animals did diversity increase within most clades with fossilizable members. While taxonomic placement of many Proterozoic eukaryotes may be arguable, the presence of characters used for that placement is not. Focus on character evolution permits inferences about the innovations in cell biology and development that underpin the taxonomic and morphological diversification of eukaryotic organisms.”
#Agić, H. Origin and Early Evolution of the Eukaryotes: Perspectives from the Fossil Record. In: Neubeck, A., McMahon, S. (eds) Prebiotic Chemistry and the Origin of Life. Advances in Astrobiology and Biogeophysics. Springer, Cham. (2021)
https://doi.org/10.1007/978-3-030-81039-9_11
Quote: “The emergence of a complex, eukaryotic cell is one of the major steps in the evolution of life on Earth. Eukaryotic organisms include a range of macroscopic life such as animals, plants, fungi, as well as a plethora of microscopic single-celled or colonial protists. The first evidence for eukaryotic life appears in the geologic record around 1650 million years ago (Ma), as organic-walled microfossils—cellular vesicles often preserved as carbonaceous compressions in siliciclastic rocks. Early eukaryotes were predominantly single-celled and minute for about a billion years, until the onset of macroscopic multicellularity in algae and animals in the Ediacaran Period (635–538 Ma). Here I review the earliest evidence of eukaryotic life, including a range of Proterozoic organic-walled microfossils and problematica. These fossils contain a suite of morphological and geochemical characters that offer clues about their palaeobiology. Complex microfossil morphology like spines can be considered a proxy for the appearance of a cytoskeleton, very early in eukaryote history, in the late Paleoproterozoic. Multidisciplinary studies on fossil features such as cell morphology, cell wall ultrastructure and its chemical composition, ancient forms of multicellularity, as well as understanding the environments these microorganisms inhabited, enable the use of the fossil record to inform the timing and mode of eukaryogenesis.”
#Lamża, Ł. Deep-branching eukaryotes and early events in protist evolution. Biol Rev. (2025)
https://doi.org/10.1111/brv.70101
Quote: “The first eukaryotes evolved from their archaean ancestors in the early Proterozoic, likely ca. 2000–1800 million years ago (Mya). Their macroscopic multicellular descendants, such as plants, heterokont algae, animals and fungi, appeared hundreds of million years later. During this intermediate period of eukaryote evolution, dozens of important protist lineages emerged, either unicellular or with only simple forms of multicellularity. Recent discoveries and phylogenetic analyses point to the branching order at the base of the eukaryote family tree and suggest a sequence of evolutionary and ecological events that likely took place during the Palaeoproterozoic.”
– Today there are up to ten million species of protists, and we have yet to identify most of them.
#Lepper JA, Rappaport HB, Oliverio AM. Half of microbial eukaryote literature focuses on only 12 human parasites. ISME J. (2025)
https://pmc.ncbi.nlm.nih.gov/articles/PMC12560768/
Quote: “We used the Protist Ribosomal Reference (PR2) Database to obtain a list of named protist species, resulting in 8456 species mentioned a total of 242 844 times. We emphasize that our analyses are limited to species with named taxonomies. The actual number of protist species is much greater, with estimates ranging from 2 to 10 million or more species [6].”
“Figure 1. The vast majority of microbial eukaryotic research is focused on a small number of species, mostly human and mammalian parasites. (A) A bar plot showing the estimated number of protist species globally versus those that have been described in NCBI and PR2 databases. There are an estimated 1.2–10 million species of protists. Of that, NCBI acknowledges about 60,000 [7]. The PR2 database, used in this study, has ~8,500 unique species of protists.”
#Keeling PJ, Eglit Y. Openly available illustrations as tools to describe eukaryotic microbial diversity. PLOS Biology. (2023)
https://journals.plos.org/plosbiology/article/figure?id=10.1371/journal.pbio.3002395.g004
– Ah a swarm of Coleps hirtus, unsettlingly poisonous killer turtles. Their body is covered by a hard mineral armour made up of plates that fit tightly together and have pretzel shaped openings. This protection makes it really hard for other protists to bite and hurt them.
#Buonanno F, Anesi A, Guella G, et al. Chemical offense by means of toxicysts in the freshwater ciliate, Coleps hirtus. J Eukaryot Microbiol. 2014
https://onlinelibrary.wiley.com/doi/10.1111/jeu.12106
Quote: “COLEPS HIRTUS is a common freshwater ciliate (40–65 x 20–35 um) belonging to the protostomatid group. Its body is barrel-shaped and covered in calcified plates assembled to form an armor, its oral aperture located at the anterior end of the cell, 15–16 rows of cilia following the longitudinal lines of the plates, and one elongated caudal cilium.”
#Kreutz, M. Coleps hirtus. Real Micro Life. Retrieved December 2025.
https://realmicrolife.com/coleps-hirtus/
Quote: “
length 40–65 µm
cell barrel-shaped
CV terminal
uniform ciliation
15–20 longitudinal rows of plates
anterior and posterior main plate with 4 „windows“ each
one caudal cilium
macronucleus spherical
apical mouth opening with basket
three spines at posterior end shape of the „windows“ in the armour pretzel-shaped”
#Plewka, M. Coleps hirtus. Life in Water. Retrieved December 2025
Quote: “Coleps hirtus, is a scavenger; the image shows a specimen that has fed from a dead copepod with orange lipid droplets. Focal plane on the plates of the lorica. (1)”
#Extended Observation Description on Coleps hirtus. Protisten.de. Retrieved January 2026
https://www.protisten.de/protists-def/observation-description-coleps-hirtus/
“Fig. 1: SEM images of the alveolar plates of Coleps hirtus. The fine structure of the plates resembles the silicate structures of diatoms, e.g. of Coscinodiscus valves. a Overview showing the front secondary plates (vNp), front main plates (vHp), rear main plates (hHp) and the rear secondary plates (hNp). Circumoral plates surround the area of the mouth. b main plate, view from the outside, c Secondary plate, view from the inside. Scale bars indicate 10 µm (at 3a), 4 µm (at 3b) and 2 µm (at 3c). After Lemloh et al., 2013.”
– Between the plates hundreds of cilia emerge, hairlike structures that beat in waves and make the hunter spin like a drill as it shoots forward. With their fast drill-like attack they can bore into their victims and rip out chunks.
The “hairs” of ciliates are typically counted in rows of cilia (each composed of dozens of individual cilia) along the body/cell. Coleps hirtus has 15 or more rows of cilia, and the total number will therefore likely be in the hundreds.
Coleps hirtus eats by attacking, killing and then ingesting the fragments of its “prey”.
#Buonanno F, Anesi A, Guella G, et al. Chemical offense by means of toxicysts in the freshwater ciliate, Coleps hirtus. J Eukaryot Microbiol. 2014
https://onlinelibrary.wiley.com/doi/10.1111/jeu.12106
Quote: “COLEPS HIRTUS is a common freshwater ciliate (40–65 x 20–35 um) belonging to the protostomatid group. Its body is barrel-shaped and covered in calcified plates assembled to form an armor, its oral aperture located at the anterior end of the cell, 15–16 rows of cilia following the longitudinal lines of the plates, and one elongated caudal cilium.
[...] Coleps does not discharge its toxic compounds into the extracellular medium, but instead extrudes the toxicysts as tube-like structures forcing their content into prey organisms, eventually leading to their paralysis (Hausmann 1978; Rosati and Modeo 2003).”
– What makes Coleps even more unsettling is that it often hunts in packs like velociraptors. It’s not like they coordinate, but: Coleps are attracted by the smell of death.
Phagotrophic protists – i.e. protists that feed by engulfing other organisms or fragments of tissue – can sense the presence of food and guide their movement towards it, from up to several centimeters away (which is very far for such tiny creatures). The “smell of death” is then e.g. the contents of either damaged or dying cells. Protists such as Coleps are also known to aggregate in large numbers around larger pieces of food, i.e. prey.
Of note, while it is possible that velociraptors engaged in pack hunting behaviour, they might as well have been solo hunters or opportunistic hunters and scavengers. It is hard to impossible to make definite statements about behaviour based on fossil evidence. Perhaps, like Coleps, many individuals were at times attracted by the same prey and “group hunting” could then have been more an emergent behaviour than a targeted strategy.
#King JL, Sipla JS, Georgi JA, et al. The endocranium and trophic ecology of Velociraptor mongoliensis. J. Anat. 2020
https://onlinelibrary.wiley.com/doi/10.1111/joa.13253
Quote: “Neuroanatomical reconstructions of extinct animals have long been recognized as powerful proxies for palaeoecology, yet our understanding of the endocranial anatomy of dromaeosaur theropod dinosaurs is still incomplete. Here, we used X-ray computed microtomography (µCT) to reconstruct and describe the endocranial anatomy, including the endosseous labyrinth of the inner ear, of the small-bodied dromaeosaur, Velociraptor mongoliensis. The anatomy of the cranial endocast and ear were compared with non-avian theropods, modern birds, and other extant archosaurs to establish trends in agility, balance, and hearing thresholds in order to reconstruct the trophic ecology of the taxon. Our results indicate that V. mongoliensis could detect a wide and high range of sound frequencies (2,368–3,965 Hz), was agile, and could likely track prey items with ease. When viewed in conjunction with fossils that suggest scavenging-like behaviours in V. mongoliensis, a complex trophic ecology that mirrors modern predators becomes apparent. These data suggest that V. mongoliensis was an active predator that would likely scavenge depending on the age and health of the individual or during prolonged climatic events such as droughts.”
#Fenchel T, Blackburn N. Motile chemosensory behaviour of phagotrophic protists: mechanisms for and efficiency in congregating at food patches. Protist. 1999
https://www.sciencedirect.com/science/article/abs/pii/S1434461099700337?via%3Dihub
Quote: “Phagotrophic protists are capable of congregating at point sources of food within a few minutes, from distances of up to several cm in the case of ciliates, or several mm in the case of microflagellates. This is exemplified by four ciliate species and a heterotrophic flagellate. Congregation is accomplished by the combined effect of more than one type of chemosensory motile behaviour including “kinetic responses”, “temporal-gradient sensing”, and “helical klinotaxis”. The results are discussed in terms of microscale patchiness in nature.”
#Buonanno F, Anesi A, Guella G, et al. Chemical offense by means of toxicysts in the freshwater ciliate, Coleps hirtus. J Eukaryot Microbiol. 2014
https://onlinelibrary.wiley.com/doi/10.1111/jeu.12106
Quote: “In this context, it is worth remembering the peculiar predatory behavior of C. hirtus, which usually leads to the observation that the same prey undergo multiple attacks by several raptorial specimens. This behavior is not a novelty for this organism and was described for the first time by Doflein (1909) with regard to multiple attacks of protozoan prey by Coleps and, more recently, by Mazanec and Trevarrow (1998) about the attack and killing of young larvae of zebrafish by hundreds of Coleps. It is likely that this behavior has evolved to assure a rapid immobilization and paralysis of the prey, that after simultaneous multiple attacks can easily accumulate lethal concentrations of toxins injected by numerous predators.”
– They like to eat all kinds of other protists or single celled victims – but they are also not afraid to attack things much larger.
#Paolo Madoni, Tom Berman, Ora Hadas, Ricky Pinkas. Food selection and growth of the planktonic ciliate Coleps hirtus isolated from a monomictic subtropical lake. Journal of Plankton Research. 1990
https://doi.org/10.1093/plankt/12.4.735
Quote: “A strain of Coleps hirtus (Ciliophora, Prorodontida) was isolated from the epilimnion of monomictic Lake Kinneret. Growth of this ciliate was tested in response to 12 species of planktonic algae and seven species of cultured bacteria from lake isolates which were offered as food. Eight species of algae (one Cryptophyceae and seven Chlorophyceae) and four bacteria supported good to excellent growth of C.hirtus . Growth rates (μ) and doubling times (DT) ranged from 0.008 to 0.029 h −1 and from 23.9 to 90.8 h respectively. C.hirtus was able to grow on bacteria at concentration levels as low as 2–8 × 10 5 cells ml −1 . No correlation was observed between growth rate of C.hirtus and cell volume of the prey.”
#Buonanno F, Anesi A, Guella G, et al. Chemical offense by means of toxicysts in the freshwater ciliate, Coleps hirtus. J Eukaryot Microbiol. 2014
https://onlinelibrary.wiley.com/doi/10.1111/jeu.12106
Quote: “Coleps feeds on bacteria, algae, flagellates, living and dead ciliates, and dead individuals of its own species, but it is also histophagous, that is, it feeds on living plant and animal (rotifer, crustacean, fish) tissue (Foissner et al. 1999; Mazanec and Trevarrow 1998). Some authors have also regarded Coleps as a scavenger feeding on tissues of dead metazoans, such as Daphnia, Diaphanosoma, and chironomid larvae (Auer et al. 2004). [...] In this context, it is worth remembering the peculiar predatory behavior of C. hirtus, which usually leads to the observation that the same prey undergo multiple attacks by several raptorial specimens. This behavior is not a novelty for this organism and was described for the first time by Doflein (1909) with regard to multiple attacks of protozoan prey by Coleps and, more recently, by Mazanec and Trevarrow (1998) about the attack and killing of young larvae of zebrafish by hundreds of Coleps. It is likely that this behavior has evolved to assure a rapid immobilization and paralysis of the prey, that after simultaneous multiple attacks can easily accumulate lethal concentrations of toxins injected by numerous predators.”
– Its skin is still soft and transparent, it is 50 times larger than Coleps.
Coleps hirtus size can vary but it is typically 40-60 μm in length. Zebrafish larvae at hatching are ca. 3.1 mm in length. If we assume a conservative (for the size ratio) length of 60 μm for Coleps:
3100 μm / 60 μm = 51.7 (times larger)
#Kreutz, M. Coleps hirtus. Real Micro Life. Retrieved December 2025.
https://realmicrolife.com/coleps-hirtus/
Quote: “
length 40–65 µm
cell barrel-shaped
CV terminal
uniform ciliation
15–20 longitudinal rows of plates
anterior and posterior main plate with 4 „windows“ each
one caudal cilium
macronucleus spherical
apical mouth opening with basket
three spines at posterior end shape of the „windows“ in the armour pretzel-shaped”
“Coleps hirtus”
#The Zebrafish Information Network. Zebrafish Developmental Staging Series. Retrieved December 2025
#Sol Gomez de la Torre Canny, Christopher Holterhoff, Richard Behringer, Daniel Wagner, and David Kozlowski. Go Fish!. Genesis – The Journal of Genetics and Development (2009)
https://onlinelibrary.wiley.com/pb-assets/assets/1526968X/Go_Fish_-1509469917000.pdf
– Around their mouth they are armed with a crown of a dozen poison syringes: Toxicysts. Kind of bubbly bags with a long coil and hollow needles filled with a deadly mix of poison. As the Coleps smash into the zebrafish their syringes discharge explosively, piercing the soft skin of the zebra fish. A unique cocktail of 19 different chemicals is injected. They dissolve membranes, making cells burst open and die, and causing gaping wounds in the skin of the tiny animal. Coleps drill into the dying tissue, boring and ripping out chunks.
Toxicysts are needle-like structures used to inject toxic substances into other organisms, e.g. prey. Not much is known about their detailed structure in Coleps, but microscopy in related ciliates suggests the needles are located in some kind of sheath or sac. The exact number of toxicysts in Coleps is not known, but microscopy images suggest they number between 8 and 10, possibly more.
Coleps hirtus releases 19 different chemicals from its toxicysts. Their mechanism of action is not entirely elucidated, but the fatty acids and diterpenoids contained in the mix likely disrupt cellular membranes or interfere with essential cellular processes in the prey, resulting in cell death or paralysis.
#Buonanno F, Anesi A, Guella G, et al. Chemical offense by means of toxicysts in the freshwater ciliate, Coleps hirtus. J Eukaryot Microbiol. 2014
https://onlinelibrary.wiley.com/doi/10.1111/jeu.12106
Quote: “Coleps hirtus is a small common freshwater ciliate belonging to the protostomatid group, its body covered by calcified plates assembled to form an armor. Coleps feeds on bacteria, algae, flagellates, living and dead ciliates, animal and plant tissues. To assist its carnivorous feeding the ciliate is equipped with offensive extrusomes (toxicysts), clustering mainly in and around its oral aperture. In this study, we isolated the discharge of the toxicysts from living cells, evaluating its cytotoxic effects against various ciliate species, and demonstrating that it is essential for the effectiveness of Coleps’ predatory behavior. The analysis of the toxicyst discharge performed by liquid chromatography-electrospray-mass spectrometry and gas chromatography-mass spectrometry, revealed the presence of a mixture of 19 saturated, monounsaturated and polyunsaturated free fatty acids with the addition of a minor amount of a diterpenoid (phytanic acid).
[...]
Coleps does not discharge its toxic compounds into the extracellular medium, but instead extrudes the toxicysts as tube-like structures forcing their content into prey organisms, eventually leading to their paralysis (Hausmann 1978; Rosati and Modeo 2003).
[...]
In this context, it is worth remembering the peculiar predatory behavior of C. hirtus, which usually leads to the observation that the same prey undergo multiple attacks by several raptorial specimens. This behavior is not a novelty for this organism and was described for the first time by Doflein (1909) with regard to multiple attacks of protozoan prey by Coleps and, more recently, by Mazanec and Trevarrow (1998) about the attack and killing of young larvae of zebrafish by hundreds of Coleps. It is likely that this behavior has evolved to assure a rapid immobilization and paralysis of the prey, that after simultaneous multiple attacks can easily accumulate lethal concentrations of toxins injected by numerous predators.
[...]
The investigation on the toxicyst discharge of C. hirtus by LC-ESI-MS revealed the presence of a great variety of SFA, MFA, and PUFAs, many bearing C16 or C18 hydrocarbon chains. Free fatty acids are known to possess antimicrobial, antiviral, antifungal, cytotoxic, and hemolytic properties at low concentration (Arouri and Mouritsen 2013; Hilmarsson et al. 2006; Thormar and Hilmarsson 2007). Among all FFAs, unsaturated species, e.g. palmitoleic (C16:1) and linoleic (C18:2) acid, are more active against bacteria and that is probably due to their ability to easily penetrate membranes (Thormar and Hilmarsson 2007). Beside their detergent properties, FFAs are also able to influence the expression of genes involved in fatty acid transport and lipids and energy metabolism (Di Russo and Black 2004; Nakamura et al. 2004).”
#Buonanno, Federico & Ortenzi, Claudio. Predator-Prey Interactions in Ciliated Protists. Provisional Chapter. InTechOpen (2018)
https://www.intechopen.com/chapters/62301
Quote: “The complete analysis of the content of the toxicysts, together with observations of the predatory behavior, was also performed on another species, Coleps hirtus, a freshwater protostomatid ciliate. C. hirtus (40–65 × 20–35 μm) has an oral apparatus placed at the anterior end of the cell and its barrel-shaped body is covered by calcified armor arranged in plates. This ciliate is able to feed off bacteria, algae, flagellates, and ciliates, but it is also histophagous, that is, it feeds on living plant and animal tissue such as rotifers, crustaceans, and fish [16, 17]. Coleps is also reported to show a scavenger feeding on tissues of dead metazoans, such as Daphnia, Diaphanosoma, and chironomid larvae [18], as well as toward dead ciliates and dead specimens of its own species. Coleps is usually equipped with toxicysts used by the ciliate to assist its carnivorous feeding, and its predatory behavior has recently been analyzed against another ciliate species used as prey, Euplotes aediculatus. Observations conducted on a mixture of predators and prey showed several contacts between the specimens of Colpes and Euplotes, but only after 5–10 min did interactions between the anterior section of a predator with a specimen of Euplotes become effective. This time was probably essential for prey detection and recognition, followed by prolonged contact between predator and prey, generally ending with the rapid backward swimming of the latter which separated the two organisms. When the attacks became numerous some individuals of Coleps remained attached to their prey (Figure 4), which decreased their swimming speed and gradually stopped swimming. After 20–30 min, the prey was fragmented and eaten by several specimens of Coleps, and a similar predatory behavior was also observed using different ciliate species as prey [19]. On the contrary the toxicysts-deficient specimens of Colpes (Figure 5) obtained by means of the application of the cold-shock method capable of inducing an exclusive massive discharge of extrusomes in ciliates [20] appear unable to catch and kill their prey [19].
Unexpectedly, the analysis of the bioactive fraction of the toxicyst discharge of Coleps hirtus
(performed by liquid chromatography-electro-spray-mass spectrometry and gas chromatography-mass spectrometry) showed the presence of a mixture of 19 saturated, monounsaturated and polyunsaturated free fatty acids (FFAs) with the addition of a minor amount of a diterpenoid (phytanic acid) but did not reveal the presence of enzymes, as reported for other predatory ciliates [19]. To date this is the only report on the presence of FFAs as toxic substances in the extrusomes of ciliated protists, but the use of this class of compounds as toxins by Coleps is shared with at least 15 freshwater, 13 marine, and 6 brackish water potentially harmful microalgae, as well with some multicellular organisms. For example, a chemical defense by a mixture of FFAs was studied and demonstrated for the harmful microalga
Fibrocapsa japonica (Raphidophyceae) [21–23], and also in animals, a defensive strategy mediated by FFAs was recently described for the fish Barbus barbus which adopted it to protect its eggs from predators [24].”
#Rosati G, Modeo L. Extrusomes in ciliates: diversification, distribution, and phylogenetic implications. J Eukaryot Microbiol. 2003
https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1550-7408.2003.tb00260.x
#Li, Z., Chen, X., Zhao, F. et al. Genomic insights into the cellular specialization of predation in raptorial protists. BMC Biol (2024).
“Fig. 1. Morphology of Haptoria and their subcellular structures. A Didinium nasutum (blue on the right) preying on Paramecium caudatum (green on the left), with Didinium utilizing toxicysts near its proboscis to immobilize its prey. B Dileptus sp. (blue on the left) preying on Tetrahymena (gray on the right). C Internal view of toxicysts within the surface of a Haptoria ciliate, displaying a toxicyst in the process of discharging. D-F Subcellular structures in a raptorial ciliate, Litonotus sp., using transmission electron microscope. D Short type II toxicysts. E Long type I toxicysts. F Mitochondria”
#Yang, Hao, Zhe Wang, Jieyin Xiao, et al. Integrated Morphological and Transcriptome Profiles Reveal a Highly-Developed Extrusome System Associated to Virulence in the Notorious Fish Parasite, Ichthyophthirius Multifiliis. Virulence. 2023
“Figure 1. Theront of I. multifiliis. (a, b) Holistic view of the theront. (c, d) Magnified perforatorium at the apex. Arrowhead indicates the extrusive contents. (e) Cytostome. (f) Caudal cilium at the terminal end. (g) Longitudinal section views of theront. Arrowhead indicates the anterior part. (h) Cytoplasm of the anterior part of theront. (i) Cross section of toxicyst. (j) Longitudinal view of toxicyst showing the tube-like core (arrowhead) located within the capsule and a fibro-granular layer at the posterior end. (k) Cortex of theront. (l) Extrusion of vacuole from cilia membrane. Arrowhead indicates the ejected vacuole. Scale bars 5 μm (a, b, g), 2 μm (c, d, h), 1 μm (e, f, j), 500 nm (k), 200 nm (i, l).”
– The zebrafish shudders frantically and desperately tries to get away but the unhinged Kaijus follow and attack over and over. And it gets worse, the chemical noise of the battle attracts more Coleps and soon the tiny fish is hounded by hundreds of predators, shooting poison spears, drilling, devouring. Within an hour the victim has been completely and utterly consumed.
#Mazanec A & Trevarrow B. Coleps, Scourge of the Baby Zebrafish. The Zebrafish Information Network. Retrieved December 2025
https://zfin.org/zf_info/monitor/vol5.1/vol5.1.html#Coleps,%20Scourge%20of%20the%20Baby%20Zebrafish
Quote: “In the past we have noticed an intermittent high fish mortality among young larval zebrafish. Our daily monitoring of conditions has implicated vicious predators, known as "Twirlies" at the University of Oregon, to be the cause of much of this larval death. Over the years they have been rumored to kill entire stocks of 4-7 day old zebrafish babies.
To better characterize the problem, we have recently identified the 'twirlies' as Coleps, free-living freshwater protozoa (Patterson, 1996). They have barrel-shaped bodies approximately 50-80 µms in length that are reinforced by a layer of calcareous plates (Figure 1). Coleps are regarded as scavengers with a preference for dead or dying tissue as well as rotifer eggs (Patterson, 1996; Jones & Hollowday, 1992). Occasionally we find these predators in fish water and especially in our paramecia cultures. In small quantities they seem to be relatively harmless, but in concentrated numbers they can be deadly to small larval fish. As soon as the larvae hatch, the Coleps are immediately attracted to them. Within a few minutes baby zebrafish can be swarmed by hundreds of Coleps. It then takes this swarm only between 30 minutes and an hour to kill and completely consume the baby zebrafish leaving virtually no evidence of their heinous act (see figure). Rather than a disease or parasite we consider this an infestation of a microscopic predator.”
“Figure 1 The first picture is a drawing of an individual Coleps. The series of 4 photos (right to left) shows the fate of two zebrafish larvae confined in a small volume of water from a Coleps culture. The first picture shows a recently killed zebrafish surrounded by a halo of Coleps (small dots). After 45 minutes (second picture), the fish in the first frame has been processed to a mere shadow of its former self (dead fish on left) and a live larva, 5 days old, has been added. The next 2 pictures are after 15 and 20 minutes. During this period, the larvae has been killed and is in the process of being eaten by a large swarm of Coleps while the first fish has become increasingly ghost-like.”
– They are one of the oldest organisms on earth producing oxygen for us all.
#Matsuo, T., Ito-Miwa, K., Hoshino, Y. et al. Archaean green-light environments drove the evolution of cyanobacteria’s light-harvesting system. Nat Ecol Evol (2025)
https://doi.org/10.1038/s41559-025-02637-3
Quote: “The planetary surface has not only been chemically and physically changed by geological events over 4.5 billion years but has also been moulded by life since its emergence. Cyanobacteria, as pioneering oxygenic photosynthetic organisms, spread across the globe by photolysis of water to generate molecular oxygen using solar radiation. This biological evolution caused a pivotal oxygenation event called the great oxidation event (GOE) around 2.4 billion years ago2. The GOE probably played an important role in the promotion of aerobic biodiversity3. However, it is worth noting that recent research suggests an emergence of aerobic metabolism and thus an oxygenated biosphere before the GOE4.”
– They form filaments that are like green Giraffe necks eating the sun, with a harder outside shell and soft inside.
Cyanobacteria exist in various shapes, sizes and colors, but most commonly they resemble green elongated sticks or spaghetti. Cells commonly aggregate to form large colonies that again can take different shapes and sizes.
#Dvorak P, Poulíčková A, Hasler P, et al. Species concepts and speciation factors in cyanobacteria, with connection to the problems of diversity and classification. Biodiversity and Conservation. (2015)
“Illustration of morphological diversity in cyanobacteria. Groups (orders) follow Rippka et al. (1979). I. Chroococcales: a Chroococcus subnudus, b Ch. limneticus, c Cyanothece aeruginosa, d Snowella litoralis, e Microcystis aeruginosa. II. Pleurocapsales: f Pleurocapsa minor. III. Oscillatoriales: g Planktothrix agardhii, h Limnothrix redekei, i Arthrospira jenneri, j Johanseninema constricum, k Phormidium sp., l, m Oscillatoria sp., n Schizothrix sp., o Tolypothrix sp., p Katagnymene accurata., IV. Nostocales: q Dolichospermum planctonicum, r Dolichospermum sp., s Nostoc sp., t Nodularia moravica. V. Stigonematales: u, v Stigonema sp. Scale bar a–u = 10 lm, v = 20 lm. (Color figure online) “
#Biology Online. Cyanobacteria. Retrieved December 2025
– Together many filaments create a fortress. They intertwine like threads and form a vast emerald carpet.
Cyanobacteria commonly aggregate to form large colonies of different shapes, sizes and colours. At the microscopic level, it can look like threads woven into a loose carpet. At the macroscopic level, it can look like dense, slimy “mats”.
#Johnson P. Mat of filamentous cyanobacteria (Blue-Green Algae). Nikon Small World Photomicrography Competition 1980. Retrieved December 2025
#Stuij T, Cleary D, Gomes N, et al. High diversity of benthic cyanobacterial mats on coral reefs of Koh Tao, Gulf of Thailand. Coral Reefs (2022)
“Underwater photographs of the various benthic cyanobacterial mats observed around the Island of Koh Tao: (a) brown mat on benthos, (b) orange mat on benthos, (c) purple mat on Fungiidae spp., (d) red mat on Pocillopora sp., (e) greenbrown mat on coral rubble, (f) green mat on benthos, (g) lila mat on a vermetid gastropod, Ceraesignum maximum, (h) greyblack mat on green algae and benthos”
– To protect themselves they vomit out a defensive slime that encases them in a defensive cocoon. See- through like glass but strong, sticky and durable. The fortress is secure, the gates are closed.
Cyanobacteria defend themselves against protist grazers/predators by – among other things – retreating into a thick layer of self-produced “slime” called EPS (exopolysaccharides).
#Sekar N, Bharti, A., Gupta, H., Gupta, K., et al. Cyanobacterial extracellular polymeric substances (EPS): Biosynthesis and their potential applications. In S. Das & H. R. Dash (Eds.), Microbial and Natural Macromolecules (pp. 349–369). Academic Press. (2021)
https://doi.org/10.1016/B978-0-12-820084-1.00015-6
Quote: “Cyanobacterial extracellular polysaccharides (EPS) are high molecular weight hetero-biopolymers having tremendous ecological significance, particularly imparting innate resilience to the microbial communities in nature, and facilitating efficient functioning of ecosystems. Unlike other microorganisms such as eubacteria, archaebacteria, or fungi, cyanobacterial EPS are unique and found as three forms of biopolymers: slime, capsule, and sheath. These EPS vary in nature and composition, depending on the environmental conditions and type of microorganisms in association; often, found associated with pigments and bioactive compounds. This imparts vigor to withstanding considerable inimical conditions such as salinity, heavy metals, drought, and other extreme environments. In recent years, cyanobacterial EPS are considered to be a high-value macromolecule, but their applications are less explored, owing to the poorly documented knowledge regarding the complex nature of these polysaccharides. An overview of the biological properties of cyanobacterial exopolysaccharides toward new state-of-the-art applications, particularly in agriculture, diagnostics, and food industries is discussed. Further, insights into the characteristics, potential applications of this biopolymer in various fields—including environment and industrial biotechnology are illustrated. There is a need to devote more focused efforts towards the in-depth compositional analyses, at both molecular and genetic level. This can help design novel, efficient and effective delivery systems for use, not only in therapeutics, but also in other diverse fields.”
#Pajdak-Stós A, Fiakowska E, Fyda J. Phormidium autumnale (Cyanobacteria) defense against three ciliate grazer species. Aquat Microb Ecol (2001)
https://doi.org/10.3354/ame023237
Quote: “Investigations of the effects of grazing by 3 species of ciliates – Pseudomicrothorax dubius Peck, Nassula citrea Kahl and Furgasonia blochmanni Faure-Fremiet – on mats of Phormidium autumnale (Agardh) Gomont showed that the cyanobacterium was capable of surviving very strong grazer pressure, thanks to both an extracellular polysaccharide (EPS) layer and behavioral defense. In the presence of ciliates, cyanobacteria trichomes were confined to a protective layer of extracellular material enclosing the mat. Trichomes attacked by a ciliate usually escaped by retreating within the EPS layer. The effectiveness of this kind of defense was reflected in dramatic changes in the condition of the ciliates: within 30 h of the start of the experiments a significant fraction was starved because they were unable to reach trichomes hidden within the shielding EPS layer.”
– A group of Pseudomicrothorax dubius wants to get into the fortress and eat the inhabitants. They are small hunters, like hairy, squished slugs with tiny innocent looking mouth holes.
Pseudomicrothorax dubius is a protist known for feeding on cyanobacteria.
#Klaus Hausmann. Food acquisition, food ingestion and food digestion by protists, Japanese Journal of Protozoology. 2002
#Guenther, G. Pseudomicrothorax dubius ciliate, LM. Science Photo Library. Retrieved December 2025
https://www.science-photo.de/bilder/13416650-Pseudomicrothorax-dubius-ciliate-LM
Quote: “Light micrograph of the ciliate Pseudomicrothorax dubius. Pseudomicrothorax devours cyanobacterial filaments, mainly of the genus Oscillatoria, within a short time. The ciliate belongs to the order Nassulida, the members of which possess a special mouth-feeder with which filamentous cyanobacteria are devoured. Microscopic contrast method : Differential interference contrast. Magnification 800x at a print width of 10 cm.”
#Edyta Fiałkowska, A. Pajdak–stós; Inducible defence against a ciliate grazer Pseudomicrothorax dubius, in two strains of Phormidium (cyanobacteria). Proc Biol Sci 1997
Quote: “Experiments were done with two strain of filamentous, mat–forming Phormidiumand their ciliate grazer Pseudomicrothorax dubius, to explain why the ciliates remain hungry in an apparent surplus of food, except for the first 24 hours after feeding. Under grazing pressure, both strains of cyanobacteria showed statistically significant increases in the number of filaments terminating in an empty sheath, compared to the control. Direct observations revealed that the mechanism behind this effect was active withdrawal of the trichomes inside the sheaths when disturbed by grazers. As P. dubius is unable to ingest trichomes with such endings, we conclude that cyanobacteria are not limited to chemical means of defence against grazers but can also defend themselves by means of movement and changes in filament morphology. This is apparently the first report on behavioural defence observed in cyanobacteria.”
– Their cilia flatter manically as they rapidly shoot through the water attacking the fortress.
Pseudomicrothorax belong to the “Ciliates”, a group of protists named after their numerous cilia: hairlike structures that cover their bodies, involved in movement and feeding.
#Bayless BA, Navarro FM, Winey M. Motile Cilia: Innovation and Insight From Ciliate Model Organisms. Front Cell Dev Biol. 2019
https://pmc.ncbi.nlm.nih.gov/articles/PMC6838636/
Quote: ”Ciliates are a powerful model organism for the study of basal bodies and motile cilia. These single-celled protists contain hundreds of cilia organized in an array making them an ideal system for both light and electron microscopy studies. Isolation and subsequent proteomic analysis of both cilia and basal bodies have been carried out to great success in ciliates. These studies reveal that ciliates share remarkable protein conservation with metazoans and have identified a number of essential basal body/ciliary proteins. Ciliates also boast a genetic and molecular toolbox that allows for facile manipulation of ciliary genes. Reverse genetics studies in ciliates have expanded our understanding of how cilia are positioned within an array, assembled, stabilized, and function at a molecular level. The advantages of cilia number coupled with a robust genetic and molecular toolbox have established ciliates as an ideal system for motile cilia and basal body research and prove a promising system for future research.”
A video of Pseudomicrothorax dubius eating cyanobacteria can be found below.
#Hausmann, Klaus: Ingestion and Digestion in the Ciliate Pseudomicrothorax dubius. IWF (Göttingen), 1981.
– The Pseudomicrothorax throw themselves against the wall and try to penetrate the glassy wall but get stuck. They are probing for weaknesses, trying to find an in or pull a living green thread out but without luck. Finally one of them discovers an in. A small weakness in the wall ripped by some larger creature. Now all hell breaks loose.
Cyanobacteria defend themselves against protist grazers/predators by – among other things – retreating into a thick layer of self-produced “slime” called EPS (exopolysaccharides). If the protists cannot find a way around or through the slime, they are unable to feed on the cyanobacteria. They have no way of destroying the EPS themselves, so they have to search for an opening.
#Pajdak-Stós A, Fiakowska E, Fyda J. Phormidium autumnale (Cyanobacteria) defense against three ciliate grazer species. Aquat Microb Ecol. 2001
https://doi.org/10.3354/ame023237
Quote: “Investigations of the effects of grazing by 3 species of ciliates – Pseudomicrothorax dubius Peck, Nassula citrea Kahl and Furgasonia blochmanni Faure-Fremiet – on mats of Phormidium autumnale (Agardh) Gomont showed that the cyanobacterium was capable of surviving very strong grazer pressure, thanks to both an extracellular polysaccharide (EPS) layer and behavioral defense. In the presence of ciliates, cyanobacteria trichomes were confined to a protective layer of extracellular material enclosing the mat. Trichomes attacked by a ciliate usually escaped by retreating within the EPS layer. The effectiveness of this kind of defense was reflected in dramatic changes in the condition of the ciliates: within 30 h of the start of the experiments a significant fraction was starved because they were unable to reach trichomes hidden within the shielding EPS layer.”
Pseudomicrothorax is also known to search along filaments of cyanobacteria for the right point to start feeding from. This behaviour can be seen in this video at around 02:44:
#Hausmann, Klaus: Ingestion and Digestion in the Ciliate Pseudomicrothorax dubius. IWF (Göttingen), 1981.
#PECK, R.K. Feeding Behavior in the Ciliate Pseudomicrothorax dubius is a Series of Morphologically and Physiologically Distinct Events. The Journal of Protozoology (1985)
https://doi.org/10.1111/j.1550-7408.1985.tb04049.x
Quote: “Based upon light and electron microscopical observations, the feeding behavior of the ciliate Pseudomicrothorax dubius, when fed the cyanobacterium Oscilatoria formosa, is resolved into two principal phases, contact swimming and phagocytosis, the latter being separable into two steps, attachment and ingestion. Following collision with an O. formosa filament. cells swim along the filament with their ventral cilia in contact with it during the contact swimming phase. Phagocytosis commences with the attachment of the cytostome to the filament, which initiates lysosomal streaming in the cytostomal-cytopharyngeal region. The filament then enters the cytopharynx concomitant with food vacuole formation during the ingestion step. Treatment of cells with trypsin or modification of the extracellular ionic medium inhibits the attachment step of phagocytosis but does not affect contact swimming. Behavior of cells when fed different cyanobacterial species as well as artificial food substrates is also examined. Contact swimming is a form of contact guidance since the shape of the food substrate determines the direction of cell movement. Additionally, a chemical factor may be present in or on the cyanobacteria and play a role in contact swimming. Evidence is presented that suggests that during the attachment step, two phenomena are involved: direct adhesion between cell surfaces and adhesion due to material liberated by exocytosis.”
– The Kaijus push in, shredding the damaged defense like plastic wrap, their mouth-rings bristling with excitement. The long bacteria try to escape, moving deeper into the fortress but it is too late.
Chains or filaments of cyanobacterial cells are called “trichomes”. They can be straight, curved or twisted. In response to grazers/predators like Pseudomicrothorax, trichomes can react in different ways. Here we refer to the cells moving away from Pseudomicrothorax, to avoid being eaten.
#Edyta Fiałkowska, A. Pajdak–stós; Inducible defence against a ciliate grazer Pseudomicrothorax dubius, in two strains of Phormidium (cyanobacteria). Proc Biol Sci 1997
https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC1688439&blobtype=pdf
Quote: “Direct observations revealed marked differences in the defence reaction between the two strains. The situations occurring after the filaments were attacked can be grouped into five categories: (i) the trichome escaped inside the sheath (figure 2a), (ii) the exposed trichome moved away from the grazer (figure 2b), (iii) the trichome was sucked out of the sheath (figure 2c), (iv) the whole trichome was ingested, and (v) no reaction of the trichome was observed.”
“Figure 2. [...] (b) Withdrawal of exposed Ph2 trichome at the beginning of direct observations. From left to right: trichome ingested by a ciliate; position of trichome 5 s after ciliate detachment; position of trichome after 15 s.”
– The predators waste no time and start sucking them in like living spaghetti. Their tiny mouth holes are rings made from twenty two tiny arms pulling in at a horrifying speed.
A video of Pseudomicrothorax dubius eating cyanobacteria can be found below. The most relevant section for this part of the script starts at around 05:55.
#Hausmann, Klaus: Ingestion and Digestion in the Ciliate Pseudomicrothorax dubius. IWF (Göttingen), 1981.
Around the mouth (cytostome) of P. dubius there is a specialized feeding organelle, the cytopharyngeal basket: a tube made of about 22 (±3) microtubule bundles.
#Hausmann K, Peck RK. Microtubules and microfilaments as major components of a phagocytic apparatus: the cytopharyngeal basket of the ciliate Pseudomicrothorax dubius. Differentiation. 1978
https://www.sciencedirect.com/science/article/abs/pii/S0301468111611948?via%3Dihub
Quote: “The cytopharyngeal basket of Pseudomicrothorax dubius, through which filamentous blue-green algae are ingested, consists of 22 (± 3) nemadesmata and nemadesmal lamellae, in the form of a tube. A cytostome, delimited by the cell membrane and surrounded by 22 (± 3) major and minor cortical corrugations, covers the end of the basket where the latter is attached to the cell cortex. Each nemadesm, at its greatest diameter, consists of about 200 microtubules which are joined together by sheet-like cross-bridges. The cross-bridges appear to be responsible for the high structural resilience of the nemadesmata. Each nemadesmal lamella is a ribbon of 20–30 microtubules, with two arm-like structures associated with one side of each microtubule. The arms are partially embedded in a fine filamentous layer. Except for a perforated zone, the wall of the basket is completely closed due to the presence of a filamentous sheath which extends between adjacent nemadesmata. Absence of the sheath allows movement of vesicles between the cytoplasm and the lumen of the basket in the perforated zone. The sheath is capable of elastic stretching during food uptake.”
#Klaus Hausmann, Food acquisition, food ingestion and food digestion by protists, Japanese Journal of Protozoology. 2002
https://www.jstage.jst.go.jp/article/jjprotozool/35/2/35_85/_pdf/-char/en
– Pseudomicrothorax doesn't have teeth, so instead it ejects hundreds of tiny vesicles filled with the equivalent of superaggressive stomach acid on the prey. Turning them into soup as they fill up their entire bodies with their prey. Imagine a lion sucking up a whole giraffe and within a few seconds.
#Klaus Hausmann. Food acquisition, food ingestion and food digestion by protists, Japanese Journal of Protozoology, 2002
#Hausmann, K.; Peck, R. The Mode of Function of the Cytopharyngeal Basket of the Ciliate Pseudomicrothorax dubius. Differentiation (1979)
https://doi.org/10.1111/j.1432-0436.1979.tb01023.x.
Quote: “The ciliate Pseudomicrothorax dubius feeds on filamentous blue-green algae, ingesting them at rates of up to 15 μm per second, by means of a cytopharyngeal basket. The wall of the basket is composed of 22 ± 3 nemadesmata, each of which is a bundle of about 200 microtubules which are cross-linked in a hexagonal pattern. The lumen of the non-feeding basket is filled with cytoplasma into which project the nemadesmal lamellae. Each nemadesmal lamella is attached to a nemadesm and consists of a single row of 20–30 microtubules. Each microtubule of the nemadesmal lamella bears a row of pairs of arm-like projections which are embedded in a filamentous matrix. During feeding, the lumen of the basket is occupied by the developing food vacuole. The nemadesmal lamellae are observed between the vacuole membrane and the nemadesmata, and the arms of the nemadesmal lamellae microtubules are oriented toward the membrane of the food vacuole or of small vesicles. A mechanism for the generation of force for phagocytosis by means of the microtubule arms is proposed. During food uptake the membrane of the food vacuole increases rapidly at rates up to 270 μm2 per second. Vacuole growth results from the fusion of membrane-bound vesicles. During phagocytosis a fast streaming of these vesicles can be observed in the cytoplasm surrounding the basket. The direction of streaming is opposite to that of ingestion of the algal filament. The vesicles enter the lumen of the basket at its anterior end, in a zone where the wall of the basket is perforated.”
#PECK, R.K. and HAUSMANN, K. Primary Lysosomes of the Ciliate Pseudomicrothorax dubius: Cytochemical Identification and Role in Phagocytosis*. The Journal of Protozoology (1980)
https://doi.org/10.1111/j.1550-7408.1980.tb05384.x
Quote: “SYNOPSIS. Filamentous cyanobacteria are ingested through the cytopharynx of the ciliate Pseudomicrothorax dubius. The cytopharynx is a complex of microtubules and microfilaments located in a highly vesiculated cytoplasm, the phagoplasm. Two types of membrane-bounded phagoplasmic vesicles can be distinguished by their differences in size, fine structure, and acid phosphatase (AcPase) content. One type has a homogeneous, electron-dense interior which is AcPase-positive. These vesicles are present in fed cells and in unfed cells devoid of food vacuoles, and thus appear to be primary lysosomes. During phagocytosis, exocytosis within the cytopharynx of the primary lysosomes results in the elaboration of a food vacuole. The vacuole grows by incorporation of lysosomal membrane; lysosomal hydrolases are liberated into the vacuole. Within less than 1 second of AcPase's entry into the food vacuole, it is detectable within the cyanobacterial cytoplasm, and within 5 seconds, destruction of the cyanobacterial filament is observed. It is hypothesized that the rapidity of hydrolase penetration of the cyanobacterial cell wall is the result of the action of molecules analogous to the “killing agents” of neutrophil leukocytes, which rapidly render bacterial envelopes permeable. AcPase, and presumably other hydrolases, are present in the cyanobacterial filament when filament destruction occurs; they thus appear implicated in this process. Hydrolases may activate an autodestruction mechanism in the cyanobacterium. Firm adherence of the food vacuole membrane to the cyanobacterial filament is demonstrated, and its role in phagocytosis is discussed.”
#Hausmann, K. Zur Digestion bei Pseudomicrothorax dubius Mermod Nahrungsvakuolen-Vesikulation (Ciliophora) im Anschluß an die Phagocytose. Zoomorphology (1980)
https://doi.org/10.1007/BF00310288
Quote: “The gulper Pseudomicrothorax dubius ingests a large volume of filamentous blue-green algae within 1–2 min. Immediately after this rapid phagocytosis, the food is enclosed in a single, extremely large food vacuole, which fills up the ciliate almost entirely. During the following hour this giant food vacuole vesiculates. Finally numerous small vacuoles are present, 1–2 μm in diam. Simultaneously the content of the vacuoles is noticeably condensed. At this time the digestion of the food starts as is indicated by numerous dictyosomes, which now surround the periphery of the food vacuoles. Due to both, the prior vesiculation of the food vacuole and the condensation of the food, the digestive enzymes can act very effectively. After 6–8 hours, when the digestion of the food is finished, numerous empty vacuoles are found. Each is characterized by a highly irregular, convoluted outline. Apparently these vacuoles are eventually recycled to the membrane pool of the cell.”
– Some Pseudomicrothorax don’t go for the ends but start sucking and dissolving bacteria in the middle, breaking their victims up and devouring them twice as fast – and a few predators suck on the same bacteria from both ends like they want to end up kissing.
#Hausmann, Klaus: Ingestion and Digestion in the Ciliate Pseudomicrothorax dubius. IWF (Göttingen), 1981.
The below paper describes a “breaking prey up in the middle” behaviour in Pseudomicrothorax feeding on a different species of cyanobacteria (Oscilatoria formosa).
#PECK, R.K. Feeding Behavior in the Ciliate Pseudomicrothorax dubius is a Series of Morphologically and Physiologically Distinct Events. The Journal of Protozoology (1985) https://doi.org/10.1111/j.1550-7408.1985.tb04049.x
Quote: “Based upon light and electron microscopical observations, the feeding behavior of the ciliate Pseudomicrothorax dubius, when fed the cyanobacterium Oscilatoria formosa, is resolved into two principal phases, contact swimming and phagocytosis, the latter being separable into two steps, attachment and ingestion. Following collision with an O. formosa filament. cells swim along the filament with their ventral cilia in contact with it during the contact swimming phase. Phagocytosis commences with the attachment of the cytostome to the filament, which initiates lysosomal streaming in the cytostomal-cytopharyngeal region. The filament then enters the cytopharynx concomitant with food vacuole formation during the ingestion step. Treatment of cells with trypsin or modification of the extracellular ionic medium inhibits the attachment step of phagocytosis but does not affect contact swimming. Behavior of cells when fed different cyanobacterial species as well as artificial food substrates is also examined. Contact swimming is a form of contact guidance since the shape of the food substrate determines the direction of cell movement. Additionally, a chemical factor may be present in or on the cyanobacteria and play a role in contact swimming. Evidence is presented that suggests that during the attachment step, two phenomena are involved: direct adhesion between cell surfaces and adhesion due to material liberated by exocytosis.”
– Now the bacteria try to defend themselves but its a bit pathetic and slow, thousands have died already. They begin to produce a stiff sheath at their ends. When a Pseudomicrothorax begins to try to suck it up, the bacteria pulls itself away, it breaks off and leaves its attacker hungry. As if our giraffe could lose its tail like a lizard to avoid the lion’s bite.
#Agnieszka Pajdak-Stós, Wojciech Fiałkowski, Edyta Fiałkowska. Rotifers weaken the efficiency of the cyanobacterium defence against ciliate grazers. FEMS Microbiology Ecology (2020)
https://doi.org/10.1093/femsec/fiaa189
Quote: “Cyanobacteria can protect themselves through limited dispersion and by increasing the compactness of the mucilage-covered cyanobacterial mat as well as by producing sheaths covering their trichomes. These features have been used in research to measure their degree of inducible defence. The influence of the presence of the rotifers Lecane inermis on the effectiveness of Phormidium sp. (Ph2) cyanobacterium defence was investigated. Experiments were conducted on the ciliates Pseudomicrothorax dubius and Furgasonia blochmanni, specialised in the ingestion of filamentous cyanobacteria. The most compact were cyanobacterial mats that were subjected exclusively to ciliates and the most dispersed were mats in the presence of rotifers alone. The presence of rotifers feeding on cyanobacterial mucilage led to the decreased effectiveness of the defence in two ways, by increasing the dispersion of cyanobacterial trichomes, thus loosening the cyanobacterial mat, and through the ingestion of the exopolysaccharide material covering the trichomes. As a result, in the presence of rotifers and the high density of ciliates, almost all the trichomes were removed. Moreover, in comparison with other treatments, a higher number of ciliates and rotifers remained active until the end of the experiments. This is the first report to show how rotifers can weaken the defence of cyanobacteria.
[...]
The more effective, cost-saving mechanism is inducible defence, which is evoked only in the presence of a predator or a grazer (Tollrian and Harvell 1999). The first report on the inducible defence of cyanobacteria described the ability of Phormidium sp. to accelerate the production of sheaths in the presence of a ciliate grazer specialising in filament ingestion. As a direct response to ciliate attacks, cyanobacterium filaments withdrew inside the sheath and thus became inaccessible to the grazers (Fiałkowska and Pajdak-Stós 1997). Cyanobacteria such as Microcystis aeruginosa and Planktothrix agardhii are able to increase their toxin production in the presence of grazers such as Daphnia magna and Moina macrocopa (Jang, Jung and Takamura 2007).”
#Edyta Fiałkowska, A. Pajdak–stós; Inducible defence against a ciliate grazer Pseudomicrothorax dubius, in two strains of Phormidium (cyanobacteria). Proc Biol Sci (1997)
https://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC1688439&blobtype=pdf
“Figure 2. (a) Reaction of Ph2 trichome attacked by a ciliate. From left to right : ciliate starts to ingest a trichome, which begins withdrawing immediately after being broken; position of trichome inside the sheath after 5 s ; trichome safely hidden inside the stiff sheath 45 s after being broken by a ciliate. (b) Withdrawal of exposed Ph2 trichome at the beginning of direct observations. From left to right : trichome ingested by a ciliate ; position of trichome 5 s after ciliate detachment ; position of trichome after 15 s. (c) Ciliate sucking a trichome out of the sheath. This is observed only when the trichome is so short that the ciliate is able to suck it out. From left to right : a ciliate has just started to suck a trichome out of the sheath; position of trichome after 5 s ; after 15 s the whole trichome is sucked out of the sheath.“
#Edyta Fiałkowska, Agnieszka Pajdak-Stós. Chemical and mechanical signals in inducing Phormidium (Cyanobacteria) defence against their grazers. FEMS Microbiology Ecology. 2014
https://doi.org/10.1111/1574-6941.12367
Quote: “The nature of stimuli evoking cyanobacterium defence was investigated in experiments on Phormidium sp. strain able to defend itself against ciliate grazers. Limited dispersion of trichomes in reaction to Pseudomicrothorax dubius separated from cyanobacterium with a mesh insert indicates the existence of a chemical cue originating from the ciliates. Grazers released into the wells where trichomes' dispersion was already limited by the cue initially had no difficulty finding food, but started to starve 24 h later. Similar situation was observed in control wells. Direct observations of trichomes attacked by the ciliates showed a distinct difference between the trichomes previously subjected to mesh-separated ciliate and the control ones. The former withdrew more frequently into a rigid sheath, whereas the latter usually withdrew into elastic tubes. This suggests that both chemical and mechanical stimuli are necessary to express cyanobacterium defence to the fullest extent. Further investigations showed that ciliates specialised in ingesting filamentous Cyanobacteria limit trichomes' dispersion, whereas filter-feeding Euplotes and Cyanobacteria-feeding rotifer do not. The cyanobacterium can detect grazer presence even without direct contact and modify its morphology in a way enabling full expression of defence reaction. This is the first report on ciliate–cyanobacterium chemical mediation.”
– And they produce more slime trying to fix the holes in the fortress and push the attackers out.
#Pajdak-Stós A, Fiakowska E, Fyda J. Phormidium autumnale (Cyanobacteria) defense against three ciliate grazer species. Aquat Microb Ecol (2001)
https://doi.org/10.3354/ame023237
Quote: “In response to ciliate attacks, cyanobacteria are also able to form more compact mats resembling clumps. The acceleration of mucilage production in the presence of grazers helps them to form a barrier to protect the cyanobacterial trichomes that are entangled inside the mat from ingestion by ciliates specialising in the ingestion of filamentous cyanobacteria (Pajdak-Stós, Fiałkowska and Fyda 2001). Similarly, the cyanobacterium Mi. aeruginosa was subjected to grazing by flagellates and it responded by synthesising and secreting exopolysaccharides to surround the cyanobacterial cells in the newly formed colonies (Yang et al. 2008).”
– This story begins with an environmental disaster: Alexandrium minutum, protists hiding behind thick cellulose armour plates are taking over the warm waters near the coast.
#Chan WS, Kwok ACM and Wong JTY. Knockdown of Dinoflagellate Cellulose Synthase CesA1 Resulted in Malformed Intracellular Cellulosic Thecal Plates and Severely Impeded Cyst-to-Swarmer Transition. Front. Microbiol. (2019)
https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00546/full
Quote: “Dinoflagellates have profound ecological importance, with many species being significant members of phytoplankton, as both primary producers and grazers, as well as causing regular seasonal blooms and red tide. Symbiotic dinoflagellates of corals form the primary productivity base in coral reef ecosystems (Davy et al., 2012; Hart et al., 2015; Hu et al., 2015). Cellulose is commonly deposited on extracellular matrix during cell wall formation. The “internal” cell wall (or amphiesma) in dinoflagellates consists of two cortical intracellular layers: (i) the highly patterned CTPs (Figures 1B–D) in AV (thecal vesicle or alveoli) (Morrill and Loeblich, 1983; Bogus et al., 2014) in thecate species and (ii) the pellicular layer with no or questionable cellulose content (Morrill and Loeblich, 1981). CTPs, the prominent cortical structures in thecate dinoflagellates, have precise architecture and dimensions, which are used for taxonomic differentiation between species. CTPs are commonly regarded to have protective functions and our nanoindentation study suggested they have similar mechanical properties to soft wood (Lau et al., 2007). CTPs can be up to microns in thickness and 30–50 microns in width (Morrill and Loeblich, 1983), and representing substantial weight of the dinoflagellate cell and renewable carbon.”
#U.S. National Office for Harmful Algal Blooms (HABs) – Woods Hole Oceanographic Institution (WHOI). Alexandrium. Retrieved January 2026.
https://hab.whoi.edu/species/species-by-name/alexandrium/
Quote: “Alexandrium
Bloom forming dinoflagellate genus
More than 30 recognized species
Found globally in coastal waters
Certain species produce saxitoxins, which may lead to:
Human poisoning cases - Paralytic Shellfish Poisoning (PSP)
Economic losses in aquaculture and fisheries industries
Marine animal mortalities
Food web disruptions”
#E. Nogueira, I. Bravo, P. Montero, et al. HABs in coastal upwelling systems: Insights from an exceptional red tide of the toxigenic dinoflagellate Alexandrium minutum. Ecological Indicators. 2022
https://www.sciencedirect.com/science/article/pii/S1470160X22002618?via%3Dihub
Quote: “Alexandrium minutum blooms generally occur in semi-enclosed sites such as estuaries, harbours and lagoons, where enhanced stratification, restricted circulation and accumulation of resting cysts in the sediment set suitable habitat conditions for the proliferation of this paralytic shellfish poisoning toxigenic species.”
– Within days billions turn into quadrillions – a toxic algae bloom is clouding the water in rust red curtains.
During a bloom of cyanobacteria, cell concentrations of up to 1 million (106) cells per mL can be reached. One billion (109) cells would then be the equivalent of 1000 mL (1 L) of densely colonized water. One quadrillion (1015) would be the equivalent of 1 million L (1000 m3) densely colonized water – or a cube with side length of 10 m. Assuming lower cell densities in the bloom, the volume occupied by quadrillions of cells would of course be bigger but still roughly on the order of magnitude of e.g. a part of a bay somewhere.
#Mishra, S., Stumpf, R.P., Schaeffer, B.A. et al. Measurement of Cyanobacterial Bloom Magnitude using Satellite Remote Sensing. Sci Rep (2019)
https://doi.org/10.1038/s41598-019-54453-y
Quote: “We have also added ‘Very High’ (V.High) category when estimated cyanobacteria concentration and area-normalized magnitude exceeded 1,000,000 cell mL−1 and 0.111, respectively.”
#Carles Guallar, Cedric Bacher, Annie Chapelle. Global and local factors driving the phenology of Alexandrium minutum (Halim) blooms and its toxicity. Harmful Algae. 2017
https://doi.org/10.1016/j.hal.2017.05.005
Quote: “The dinoflagellate Alexandrium minutum is a toxic bloom-forming species distributed worldwide. The mechanisms driving and promoting the species blooms and their toxicity are studied and presented here. Most previously published work focuses on local and/or short-term scales. In this study, a broad temporal and spatial approach is addressed using time series covering several sites over several years and combining environmental variables and A. minutum abundances from the French English Channel − Atlantic coasts. Data were explored by means of phenology and threshold analysis.
The A. minutum bloom characteristics are defined. Only one bloom per year is measured and it may reach more than a million of cells L−1. Bloom period extends from April to October and the bloom length ranges from two weeks to six months. In the ecosystems studied, water temperature and river flow, as regional and local factors respectively, are the main environmental drivers influencing the magnitude, growth rate and length of the blooms. Bloom toxicity is linked to the bloom maximum abundance and river flow. This work provides new knowledge for further managing tools for A. minutum blooms in the ecosystems studied.”
Various Alexandrium species can cause toxic red blooms. Below is a picture of a toxic bloom caused by A. monilatum.
#David Malmquist, Virginia Institute of Marine Science. VIMS reports intense and widespread algal blooms. 2015
https://phys.org/news/2015-09-vims-intense-widespread-algal-blooms.html
“An exceptionally dense bloom of Alexandrium monilatum was observed in lower Chesapeake Bay along the north shore of the York River between Sarah's Creek and the Perrin River on 8/17/2015. Credit: © W. Vogelbein/VIMS.”
#Lewis, A.M., Coates, L.N., Turner, A.D., et al. A review of the global distribution of Alexandrium minutum (Dinophyceae) and comments on ecology and associated paralytic shellfish toxin profiles, with a focus on Northern Europe. J. Phycol. (2018)
https://onlinelibrary.wiley.com/doi/10.1111/jpy.12768
Quote: “Alexandrium minutum is a globally distributed harmful algal bloom species with many strains that are known to produce paralytic shellfish toxins (PSTs) and consequently represent a concern to human and ecosystem health. This review highlights that A. minutum typically occurs in sheltered locations, with cell growth occurring during periods of stable water conditions. Sediment characteristics are important in the persistence of this species within a location, with fine sediments providing cyst deposits for ongoing inoculation to the water column. Toxic strains of A. minutum do not produce a consistent toxin profile, different populations produce a range of PSTs in differing quantities. Novel cluster analysis of published A. minutum toxin profiles indicates five PST profile clusters globally. Some clusters are grouped geographically (Northern Europe) while others are widely spread. Isolates from Taiwan have a range of toxin profile clusters and this area appears to have the most diverse set of PST producing A. minutum populations. These toxin profiles indicate that within the United Kingdom there are two populations of A. minutum grouping with strains from Northern France and Southern Ireland. There is a degree of interconnectivity in this region due to oceanic circulation and a high level of shipping and recreational boating. Further research into the interrelationships between the A. minutum populations in this global region would be of value.”
– Each of them is a chemical weapons factory vomiting saxitoxin, one of the most potent neurotoxins on earth.
#Antonella Penna, Federico Perini, Carmela Dell’Aversano, et al. The sxt Gene and Paralytic Shellfish Poisoning Toxins as Markers for the Monitoring of Toxic Alexandrium Species Blooms. Environmental Science & Technology (2015)
https://pubs.acs.org/doi/10.1021/acs.est.5b03298
Quote: “Paralytic shellfish poisoning (PSP) is a serious human illness caused by the ingestion of seafood contaminated with saxitoxin and its derivatives (STXs). These toxins are produced by some species of marine dinoflagellates within the genus Alexandrium. In the Mediterranean Sea, toxic Alexandrium spp. blooms, especially of A. minutum, are frequent and intense with negative impact to coastal ecosystem, aquaculture practices and other economic activities. We conducted a large scale study on the sxt gene and toxin distribution and content in toxic dinoflagellate A. minutum of the Mediterranean Sea using both quantitative PCR (qPCR) and HILIC-HRMS techniques. We developed a new qPCR assay for the estimation of the sxtA1 gene copy number in seawater samples during a bloom event in Syracuse Bay (Mediterranean Sea) with an analytical sensitivity of 2.0 × 10° sxtA1 gene copy number per reaction. The linear correlation between sxtA1 gene copy number and microalgal abundance and between the sxtA1 gene and STX content allowed us to rapidly determine the STX-producing cell concentrations of two Alexandrium species in environmental samples. In these samples, the amount of sxtA1 gene was in the range of 1.38 × 105 – 2.55 × 108 copies/L and the STX concentrations ranged from 41–201 nmol/L. This study described a potential PSP scenario in the Mediterranean Sea.”
#Wiese, Maria, Paul M. D’Agostino, Troco K. Mihali, et al. Neurotoxic Alkaloids: Saxitoxin and Its Analogs. Marine Drugs. 2010
https://doi.org/10.3390/md8072185
Quote: “2. Saxitoxin and Its Analogs, the Paralytic Shellfish Toxins
STX is one of the most potent natural neurotoxins known. A dose of approximately 1 mg of the toxin from a single serving of contaminated shellfish is fatal to humans.”
– Fish flee or die, shellfish store it inside and become incredibly dangerous for humans to eat.
#Deng H, Shang X, Zhu H, et al. Saxitoxin: A Comprehensive Review of Its History, Structure, Toxicology, Biosynthesis, Detection, and Preventive Implications. Mar Drugs. 2025
https://pmc.ncbi.nlm.nih.gov/articles/PMC12300590/
Quote: “In the field of ecotoxicology, the accumulation of STX at the top of the food chain can lead to population cascading effects. For instance, high concentrations of STX in shellfish can cause foodborne poisoning, including PSP [93,94]. Toxins’ metabolic transformation significantly affects their toxicity level. The latest studies show that when mussels are exposed to dynamic algal cell densities (simulating natural blooms), the concentration of PSTs (paralytic shellfish toxins) in their bodies increases by 1.8 times compared with exposure to fixed densities. Moreover, low-toxicity sulfocarbamoyl toxins (such as GTX5) are converted into highly toxic derivatives (e.g., dcSTX) through decarbamoylation reactions, a process associated with the inhibition of sulfotransferase activity in the hepatopancreas [95]. The consumption of contaminated fish may lead to the mass death of marine predators that feed on fish (such as seabirds and cetaceans) [96,97,98]. Exposure to STX during the development of zebrafish can lead to changes in the expression of genes related to axon growth and affect the functionality of NaVs [99]. Studies on Saxidomus gigantea (Alaska butter clams) have shown that when humans consume 200 g of tissue containing 900 μg of saxitoxin (STX), the probability of severe symptoms in average males reaches 11%, and the mortality risk is 0.27%. This confirms the potential threats of STX to the ecological chain and human health [100].
The acute guideline value for STXs proposed by the WHO is 0.003 mg/L (3 μg/L) for the total STXs (including congeners, free forms, and cell-bound forms). Exposure routes include drinking contaminated surface water, consuming contaminated marine shellfish, and having contact with high-concentration water bodies during recreational activities. In terms of protection, avoiding contact and accidental ingestion is fundamental. So far, there is no specifically approved antidote, and treatment after poisoning mainly focuses on symptomatic and supportive care [101,102]. Health risks should be addressed through water source protection and water treatment process control, while paying attention to their impacts on the sensory quality of drinking water."
– But this explosion is waking up our final monster, that has waited out times of famine in the form of a spore. Now that prey is all around Polykrikos kofoidii, the mecha fusion Kaiju, awakes.
These “spores” are the dormant, thick-walled resting cysts (also called hypnozygote cysts) in Polykrikos. Cyst formation is triggered by a lack of food, and they allow it to endure harsh conditions before hatching into new vegetative cells. The cues responsible for hatching of Polykrikos cysts are not completely understood, but likely include favorable environmental conditions such as light, temperature, and food availability.
#Kazumi Matsuoka, Hisae Kawami, Satoshi Nagai, et al. Re-examination of cyst–motile relationships of Polykrikos kofoidii Chatton and Polykrikos schwartzii Bütschli (Gymnodiniales, Dinophyceae). Review of Palaeobotany and Palynology. 2009
https://doi.org/10.1016/j.revpalbo.2008.12.013
Quote: “The unarmored heterotrophic dinoflagellate Polykrikos is common in coastal waters throughout the world, and Polykrikos cysts often occur in surface sediments from tropical to sub-arctic coastal regions. Two different species, Polykrikos schwartzii Bütschli and P. kofoidii Chatton, that produce resting cysts, are recognized as indicators of eutrophic to hypertrophic coastal waters (Matsuoka et al., 2003, Pospelova et al., 2004). These cysts possess distinct morphological features characterized by a large, dark brown, elongate body with coarsely reticulate, and shelf- or rod-like surface ornaments, and a tremic archeopyle.”
#Tillmann, U. and Hoppenrath, M. Life cycle of the pseudocolonial dinoflagellate Polykrikos kofoidii (Gymnodiniales, Dinoflagellata). Journal of Phycology (2013)
https://epic.awi.de/id/eprint/32804/
Quote: “The athecate, pseudocolonial polykrikoid dinoflagellates show a greater morphological complexity than many other dinoflagellate cells and contain not only elaborate extrusomes but sulci, cinguli, flagellar pairs, and nuclei in multiple copies. Among polykrikoids, Polykrikos kofoidii is a common species that plays an important role as a grazer of toxic planktonic algae but whose life cycle is poorly known. In this study, the main life cycle stages of P. kofoidii were examined and documented for the first time. The formation of gametes, 2-zooid-1-nucleus stages very different from vegetative cells, was observed and the process of gamete fusion, isogamy, was recorded. Karyogamy followed shortly after completed plasmogamy. A complex reorganization of furrows (cinguli and sulci) and flagella followed zygote formation, resulting in a 4-zooid zygote with one nucleus. The fate of zygotes under different nutritional conditions was also investigated; well-fed zygotes were able to reenter the vegetative cycle via meiotic divisions as indicated by nuclear cyclosis. However, nuclear cyclosis was preceded by a presumably mitotic division of the primary zygote nucleus which by definition would imply that P. kofoidii has a diplohaplontic life cycle. Nuclear cyclosis in germlings hatched from spiny resting cysts indicate that these cysts are of zygote origin (hypnozygotes). Hypnozygote formation, cyst hatching, the morphology of the germling (a 1-zooid cell), and its development into a normal pseudocolony are documented here for the first time. There is evidence that P. kofoidii has a system of complex heterothallism.”
#Nagai, S., Matsuyama, Y., Takayama, H., & Kotani, Y. Morphology of Polykrikos kofoidii and P. schwartzii (Dinophyceae, Polykrikaceae) cysts obtained in culture. Phycologia (2002)
https://doi.org/10.2216/i0031-8884-41-4-319.1
Quote: “We induced encystment in Polykrikos kofoidii and P. schwartzii under laboratory conditions by repeated starvation and feeding of strains previously maintained on a prey culture of Cochlodinium sp. We demonstrate the morphological differences of the pseudocolonies and cysts and also describe the time course of the encystment process in both species. Polykrikos kofoidii cysts were ovoid, with the posterior part wider than the anterior part, thus showing a longitudinal asymmetry, and the cyst wall was commonly covered with coarse reticulate ornaments. They possessed a network of ridges formed by the periphragm and bifurcate, trifurcate, or spinous processes were usually well developed. In contrast, P. schwartzii cysts were typically elongate-elliptical or spindle-shaped and showed a rather evident longitudinal symmetry. They were covered with cylindrical, hatchet-shaped or spinous processes, arranged to form shelf-like ornamentation as seen in the light microscope. The morphological differences between the cysts of the two dinoflagellates allow unambiguous identification of the cysts, judging by data from several strains of both P. kofoidii and P. schwartzii. Cyst formation in both species progressed according to a similar time course: 1.5–2.5 hours elapsed from the time when pseudocolonies stopped swimming and sank to the bottom to when the cysts completed their ornamentation.”
#Wenjing Guo, Qisheng Yu, Yue Yu, et al. Recent advances in dinoflagellate cyst: Integrating review with visual taxonomic perspectives. Ecological Informatics. 2025
https://doi.org/10.1016/j.ecoinf.2025.103460
Quote: “Cyst germination is the process by which resting cysts, influenced by various internal and external factors, resume active metabolic activities, germinate, and undergo cell division, even resulting in rapid population growth. Chai et al. (2020) observed that rapid morphological changes occur during the germination of Pheopolykrikos hartmannii cysts, which can be defined as the “amoeboid stage.” These changes can occur multiple times within one second, and the entire germination process, which includes breaking through the cyst wall and subsequent rapid morphological transformations, is completed in approximately 15 s.”
– It is a merger of four individual semi beings that act as one bigger cell and looks like a stack of fused macarons with very disturbing filling.
Pseudocolonies of Polykrikos can be made of various numbers of individuals (zooids), typical is 4 or 8. With 4 zooids, it looks like 8 macarons (stacks of 4, duplicated next to each other) or 4 macarons, depending on the viewing angle.
#Tillmann, U. and Hoppenrath, M. Life cycle of the pseudocolonial dinoflagellate Polykrikos kofoidii (Gymnodiniales, Dinoflagellata). Journal of Phycology (2013)
#Shimoda Plankton Team – Polykrikos kofoidii. Autotranslated from Japanese to Germany by Chrome browser. Retrieved January 2026.
https://www.biol.tsukuba.ac.jp/~algae/PS/Dinophyta/Polykrikos_kofoidii/index.html
#Center for Freshwater Biology – University of New Hampshire. Retrieved January 2026.
https://cfb.unh.edu/phycokey/Choices/Dinophyceae/NonPS-dinos/POLYKRIKOS/Polykrikos_Image_page.html
#Nagai, S., Matsuyama, Y., Takayama, H., & Kotani, Y. Morphology of Polykrikos kofoidii and P. schwartzii (Dinophyceae, Polykrikaceae) cysts obtained in culture. Phycologia (2002)
– Eight flagella emerging from the grooves between them enable it to move quickly in all directions.
Pseudocolonies of Polykrikos can be made of various numbers of individuals (zooids), typical is 4 or 8. Each zooid has one pair of flagella, so 4 zooids have 8 flagella.
#Bradbury PC, Westfall JA, Townsend JW. Ultrastructure of the dinoflagellate Polykrikos. II. The nucleus and its connections to the flagellar apparatus. J Ultrastruct Res. 1983
https://pubmed.ncbi.nlm.nih.gov/6686618/
Quote: “Electron microscopy of the colonial dinoflagellate Polykrikos kofoidi revealed a nuclear cortex formed of two electron-dense cortical layers directly beneath the nuclear envelope. Nuclear pores were confined to vesicular outpocketings of the nuclear envelope over circular discontinuities in the cortical layers. A conspicuous fibrous ribbon extended from the nucleus to the flagellar apparatus of each zooid. The ribbons resembled in their structure and position the attractophores of termite flagellates. Each flagellar apparatus consisted of two flagella, two elongate axial kinetosomes, an oblique kinetosome, and two roots of markedly different periodicities.”
#Tillmann, U. and Hoppenrath, M. Life cycle of the pseudocolonial dinoflagellate Polykrikos kofoidii (Gymnodiniales, Dinoflagellata). Journal of Phycology (2013)
– Its favorite prey are protists that cause toxic blooms, making it an accidental ally to humanity.
#Jeong, H.J., Kim, S.K., Kim, J.S., et al. Growth and Grazing Rates of the Heterotrophic Dinoflagellate Polykrikos kofoidii on Red-Tide and Toxic Dinoflagellates. Journal of Eukaryotic Microbiology (2001)
https://doi.org/10.1111/j.1550-7408.2001.tb00318.x
Quote: “ABSTRACT. We investigated growth rates, grazing rates, and prey selection of Polykrikos kofoidii when feeding on several species of red-tide and/or toxic dinoflagellates. Polykrikos kofoidii ingested all prey species used in this study, exhibiting positive growth on Lingulodinium polyedrum, Scrippsiella trochoidea, Ceratium furca, Gymnodinium catenatum, Gyrodinium impudicum, Prorocentrum micans, and the toxic dinoflagellate Amphidinium carterae, but not on P. minimum. Specific growth rates of P. kofoidii increased rapidly with increasing density of L. polyedrum, S. trochoidea, C. furca, and G. catenatum before saturating between 500–2,000 ng C ml 1. Specific growth rates increased continuously when P. kofoidii was fed the other prey species. Maximum specific growth rates of P. kofoidii on G. catenatum (1.12 d−1), S. trochoidea (0.97 d−1), and L. polyedrum (0.83 d−1) were higher than those on C. furca (0.35 d−1), A. carterae (0.10 d−1), P. micans (0.06 d−1), G. impudicum (0.06 d−1), and P. minimum (−0.03 d−1). Threshold prey concentrations (where net growth = 0) were 54–288 ng C ml−1. Maximum ingestion and clearance rates of P. kofoidii on these dinoflagellates were 5–24 ng C pseudocolony−1 d−1 and 1.0–5.9 μl pseudocolony−1 h−1, respectively. Polykrikos kofoidii strongly selected L. polyedrum over S. trochoidea in prey mixtures. Polykrikos kofoidii exhibited higher maximum growth, ingestion, and clearance rates than previously reported for the mixotrophic dinoflagellate Fragilidium cf. mexicanum or the heterotrophic dinoflageilates Protoperidinium cf. divergens and P. crassipes, when grown on the same prey species. Grazing coefficients calculated by combining field data on abundances of Polykrikos spp. and co-occurring red-tide dinoflagellate prey with laboratory data on ingestion rates obtained in the present study suggest that Polykrikos spp. sometimes have a considerable grazing impact on prey populations.”
#Kang HC, Jin Jeong H, So Jin K, et al. Differential feeding by common heterotrophic protists on 12 different Alexandrium species. Harmful Algae. 2018
https://pubmed.ncbi.nlm.nih.gov/30196918/
Quote: “The genus Alexandrium often forms harmful algal blooms causing human illness and large-scale mortality of fish and shellfish. Thus, Alexandrium bloom dynamics are primary concerns for scientists, government officials, aquaculture farmers, and the public. To understand bloom dynamics, mortality due to predation needs to be assessed; however, interactions between many Alexandrium species and their potential predators have not previously been reported. Thus, feeding by five common heterotrophic dinoflagellates (Oxyrrhis marina, Gyrodinium dominans, Polykrikos kofoidii, Pfiesteria piscicida, and Oblea rotunda) and a naked ciliate (Strombidinopsis sp.) on 12 Alexandrium species was examined. Furthermore, the growth and ingestion rates of P. kofoidii on A. minutum CCMP 1888 (previously A. lusitanicum), A. minutum CCMP 113, and A. tamarense were measured as a function of prey concentration. The growth rates of P. kofoidii on the other Alexandrium species at single high prey concentrations were measured, at which the growth rates on A. minutum CCMP 1888 and A. tamarense were saturated. Feeding occurrence by these predators on 12 Alexandrium species could be categorized into 6 different prey groups. Each Alexandrium species was consumed by at least one predator; however, there was no Alexandrium species that was eaten by all six predators. Cells of A. minutum CCMP 1888, A. minutum CCMP 113, and A. tamarense were fed upon by four predators, but A. affine and A. pacificum by only one predator species, P. kofoidii or Strombidinopsis sp. Furthermore, A. minutum CCMP 1888 and A. tamarense supported high growth rates of P. kofoidii, but the other Alexandrium species did not support, but rather inhibited P. kofoidii growth. With increasing prey concentrations, the growth and ingestion rates of P. kofoidii on A. minutum CCMP 1888 and A. tamarense increased and became saturated, whereas those on A. minutum CCMP 113 continuously decreased. The maximum growth rates of P. kofoidii on A. tamarense and A. minutum CCMP 1888 were 1.010 and 0.765 d-1, respectively, and P. kofoidii maximum ingestion rates were 26.2 and 11.1 ng C predator-1d-1, respectively. In contrast, the growth rates of P. kofoidii on the other Alexandrium species at single high prey concentrations were almost zero (A. pacificum) or negative. Based on the feeding occurrence and growth and ingestion rates of predators on 12 Alexandrium species, it is suggested that common heterotrophic protistan predators respond differently to different Alexandrium species, and thus ecological niches of the Alexandrium species may be different from each other. These results may provide an insight into the roles of protistan predators in bloom dynamics of Alexandrium species.”
#Uwe John, Urban Tillmann, Jennifer Hülskötter, et al. Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population. Proc Biol Sci. 2015
https://doi.org/10.1098/rspb.2014.1268
Quote: “Dinoflagellates are a major cause of harmful algal blooms (HABs), with consequences for coastal marine ecosystem functioning and services. Alexandrium fundyense (previously Alexandrium tamarense) is one of the most abundant and widespread toxigenic species in the temperate Northern and Southern Hemisphere and produces paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive compounds may support the success of A. fundyense and its ability to form blooms. Here we investigate the impact of grazing on monoclonal and mixed set-ups of highly (Alex2) and moderately (Alex4) allelochemically active A. fundyense strains and a non-allelochemically active conspecific (Alex5) by the heterotrophic dinoflagellate Polykrikos kofoidii. While Alex4 and particularly Alex5 were strongly grazed by P. kofoidii when offered alone, both strains grew well in the mixed assemblages (Alex4 + Alex5 and Alex2 + Alex5). Hence, the allelochemical active strains facilitated growth of the non-active strain by protecting the population as a whole against grazing. Based on our results, we argue that facilitation among clonal lineages within a species may partly explain the high genotypic and phenotypic diversity of Alexandrium populations. Populations of Alexandrium may comprise multiple cooperative traits that act in concert with intraspecific facilitation, and hence promote the success of this notorious HAB species.”
#Jeong HJ, Park KH, Kim JS, et al. Reduction in the toxicity of the dinoflagellate Gymnodinium catenatum when fed on by the heterotrophic dinoflagellate Polykrikos kofoidii. Aquat Microb Ecol. (2003)
https://doi.org/10.3354/ame031307
Quote: “To investigate the ability of the heterotrophic dinoflagellate Polykrikos kofoidii to reduce the toxicity produced by the dinoflagellate Gymnodinium catenatum (toxicity = 2.0 to 3.9 Mouse Units [MU]/105G. catenatum cells), we used the mouse bioassay to measure the toxicity retained in a population of P. kofoidii, originally fed G. catenatum for 2 d (ingestion rate = 5.6 cells grazer-1 d-1) and then starved. As a control, we measured the toxicity retained in a population of P. kofoidii originally fed a non-toxic strain of Scrippsiella trochoidea. The toxicity retained in a population of P. kofoidii at Hour 0 (P. kofoidii starved for 0 to 48 h after being fed) was 17.3 MU/105P. kofoidii cells. With increasing elapsed time after starvation the toxicity rapidly decreased to 3.6 MU/105P. kofoidii cells at Hour 24, slowly decreased between Hours 36 and 81, and was not detectable at Hour 96. The decay constant in the exponential equation of the regression line for the toxicity in 105P. kofoidii cells between Hours 0 and 96 was 0.059. No toxicity was detected in P. kofoidii fed S. trochoidea. This evidence suggests that the starvation of P. kofoidii fed G. catenatum may provide dissipation of the toxicity caused by this prey in marine food webs.”
#Matsuoka, K., Cho, H. J., & Jacobson, D. M. Observations of the feeding behavior and growth rates of the heterotrophic dinoflagellate Polykrikos kofoidii (Polykrikaceae, Dinophyceae). Phycologia (2000)
https://doi.org/10.2216/i0031-8884-39-1-82.1
Quote: “This paper describes the feeding behavior of the heterotrophic dinoflagellate Polykrikos kofoidii Chatton on Gymnodinium catenatum Graham. Polykrikos kofoidii used a nematocyst to pull the prey into its body through the posterior sulcus, finally engulfing the prey completely. We measured growth rates of P. kofoidii on diverse assemblages of dinoflagellate prey. Gymnodinium catenatum was one of the best food sources for P. kofoidii, supporting a rapid growth rate in excess of one doubling per day. This suggests that G. catenatum populations may be controlled by P. kofoidii predation in natural bloom conditions. However, P. kofoidii cannot be a potential bloom-controlling factor in all toxic dinoflagellate blooms because it is rapidly killed by at least three Alexandrium strains.”
– The taeniocyst–nematocyst complex. A double barrel, harpoon gun.
Polykrikos has two special connected organelles for catching prey: the taeniocyst and the nematocyst. The mature taeniocyst–nematocyst complex is positioned in a membrane-bound compartment (the "chute") near the flagellar bases, ready for rapid deployment. The taeniocyst (the top part; the “first stage”) first # contact with the prey, often discharging its contents through a channel at the tip. This is immediately followed by the nematocyst (the “second stage”) firing, which punctures the prey’s cell wall. The prey is then retrieved using a tow filament, allowing Polykrikos to engulf and ingest it.
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
“Fig. 1 Diversity and independent origins of extrusomes.
(A to E) Nematocysts in the dinoflagellate P. kofoidii, including a live whole cell (A) and a cell that was preserved in Lugol’s iodide solution while capturing a prey cell of A. tamarense (B). (C) Enhanced contrast image shows the defensive trichocysts deployed by A. tamarense (arrows) in response to attack by P. kofoidii. (D and E) Isolated nematocysts from P. kofoidii, seen as unfired (D) and discharged (E).”
#Hoppenrath M, Bachvaroff TR, Handy SM, et al. Molecular phylogeny of ocelloid-bearing dinoflagellates (Warnowiaceae) as inferred from SSU and LSU rDNA sequences. BMC Evol Biol. 2009
https://pmc.ncbi.nlm.nih.gov/articles/PMC2694157/pdf/1471-2148-9-116.pdf
“(l) An extruded nematocyst of Polykrikos kofoidii. [...] Scale bars 10 μm.”
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
https://www.science.org/doi/10.1126/sciadv.1602552
“movie S1 [S2]. FIB-SEM reconstruction of the nematocyst-taeniocyst complex in P. kofoidii.”
https://www.science.org/doi/suppl/10.1126/sciadv.1602552/suppl_file/1602552_movie_s2.mov
– Polykrikos eerily behaves like a shark. Instead of just going for Alexandrium straight on, it begins to circle it, looping around it closer and closer as if it was sizing up its prey. Let’s slow down time so we don’t miss anything…
The below videos show Polykrikos swimming and circling around prey. The prey species shown is not Alexandrium but a different species of dinoflagellate (Lingulodinium polyedra). The hunting behaviour of P. kofoidii is likely to be very similar if not identical when it hunts Alexandrium.
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
https://www.science.org/doi/10.1126/sciadv.1602552
“movie S4 [S1]. P. kofoidii hunting L. polyedra.”
https://www.science.org/doi/suppl/10.1126/sciadv.1602552/suppl_file/1602552_movie_s1.mpg
#Tillmann U. UBC Science. Tiny plankton deploys sophisticated harpoon. YouTube. 2017
https://www.youtube.com/watch?v=uXsiVaAioNk
– Suddenly Polykrikos attacks. The upper part of its nematocyst-taeniocyst complex discharges, its top explodes off and a finger-like dart smashes into the hard shell of the Alexandrium. It ruptures and covers the prey in a layer of slime.
The upper part of the complex is the taeniocyst. Its function, and the function of what it secretes (the “slime”), is not fully understood, but it is likely involved in adhering to the prey and possibly immobilizing it.
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
https://www.science.org/doi/10.1126/sciadv.1602552
Quote: “Positioned distally to each nematocyst is a previously described organelle—the taeniocyst—that emerges from a finger-like projection near the top of each Polykrikos cell (Fig. 2A). Although the taeniocyst makes first contact with the prey, its functions are unclear. We provide evidence that taeniocysts are also ballistic structures. On five occasions, we observed that taeniocysts violently discharge when isolated from the cell (movie S5) by launching their contents through an apical channel (Fig. 2B). The taeniocyst and nematocyst seem to work in tandem, with (i) the taeniocyst initially adhering to the prey, followed by (ii) discharge of the nematocyst, which punctures the prey, and last (iii), the prey is retrieved using a tow filament.”
“SEM micrograph of an isolated taeniocyst that has discharged its amorphous contents.”
[...] “movie S5. Discharge of a taeniocyst isolated from P. kofoidii.”
https://www.science.org/doi/suppl/10.1126/sciadv.1602552/suppl_file/1602552_movie_s5.mpg
– Just a moment later the second stage fires – a long coil with a sharp head unspools explosively, traversing the distance, pierces deep into the prey cell and anchors itself firmly.
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
https://www.science.org/doi/10.1126/sciadv.1602552
“movie S2. [S3] Discharge of nematocyst isolated from P. kofoidii.
https://www.science.org/doi/suppl/10.1126/sciadv.1602552/suppl_file/1602552_movie_s3.mpg
“movie S3. [S4] Discharge of nematocyst isolated from P. kofoidii.”
https://www.science.org/doi/suppl/10.1126/sciadv.1602552/suppl_file/1602552_movie_s4.mpg
The video below shows Polykrikos kofoidii hunting not Alexandrium but a different species of dinoflagellate (Lingulodinium polyedra). The hunting behaviour of Polykrikos kofoidii is likely to be very similar if not identical when it hunts Alexandrium.
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
https://www.science.org/doi/10.1126/sciadv.1602552
“movie S4 [S1]. P. kofoidii hunting L. polyedra.”
https://www.science.org/doi/suppl/10.1126/sciadv.1602552/suppl_file/1602552_movie_s1.mpg
– Alexandrium desperately launches its defenses, crystalline trichocysts, hard little hedgehog spikes supposed to free itself, but to no avail.
Trichocysts are ejectile organelles widespread in dinoflagellates and related protists. They are usually membrane‑bound, crystalline bodies that can rapidly discharge as long rods or filaments, and are implicated in defence, prey capture, attachment, and formation of mucilage structures.
#Khalili, Nahid & Usup, Gires. Ultrastructure and Molecular Analysis of the Harmful Armored Dinoflagellate Alexandrium minutum. Journal of Advanced Microscopy Research (2015)
Quote: “Dinoflagellates are microscopic unicellular microalgae found in aquatic environments worldwide. Several marine dinoflagellate species are producers of a wide variety of toxins that can cause seafood poisoning, including fatalities in humans. In this study a combination of ultrastructure studies using transmission electron microscopy (TEM), and molecular analysis of transcriptomics data was used to gain understanding on the flagella apparatus of the toxic marine dinoflagellate Alexandrium minutum (Halim). For molecular analysis, total RNA was harvested from exponential phase cultures during the light and dark culture periods. Ultrastructure observation by TEM showed that the Cells had the typical dinoflagellate organelles. The apical groove is U-shaped and connected to the anterior sulcal extension on the dorsal side of the epicene. The chloroplast contained two or three apprised thylakoids, and was surrounded by three membranes, the eyespot was located dorsally and composed of one or two layers of globules situated within the chloroplast, in the periphery of the cell, trichocysts, mucocysts, and unidentified multilayered materials.”
Fig. 1C below shows Alexandrium tamarense (synonym A. fundyense) firing trichocysts (white arrows) in response to a Polykrikos attack.
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
“Fig. 1 Diversity and independent origins of extrusomes.
(A to E) Nematocysts in the dinoflagellate P. kofoidii, including a live whole cell (A) and a cell that was preserved in Lugol’s iodide solution while capturing a prey cell of A. tamarense (B). (C) Enhanced contrast image shows the defensive trichocysts deployed by A. tamarense (arrows) in response to attack by P. kofoidii. (D and E) Isolated nematocysts from P. kofoidii, seen as unfired (D) and discharged (E).”
#Britannica Editors. "trichocyst". Encyclopedia Britannica, 12 May. 2023. Accessed January 2026.
“Discharged trichocysts of Paramecium (highly magnified)”
– Polykrikos is too powerful and hungry – slowly the line begins to retract, pulling the victim into its now emerging mouth hole until its entire body is inside the monster, giving it a weird bulky appearance.
The videos below show Polykrikos kofoidii hunting not Alexandrium but a different species of dinoflagellate (Lingulodinium polyedra). The hunting behaviour of Polykrikos kofoidii is likely to be very similar if not identical when it hunts Alexandrium.
#Gregory S. Gavelis et al. Microbial arms race: Ballistic “nematocysts” in dinoflagellates represent a new extreme in organelle complexity. Sci. Adv. (2017)
https://www.science.org/doi/10.1126/sciadv.1602552
“Movie [...] P. kofoidii hunting L. polyedra.”
https://www.science.org/doi/suppl/10.1126/sciadv.1602552/suppl_file/1602552_movie_s1.mpg
#Tillmann U. UBC Science. Tiny plankton deploys sophisticated harpoon. YouTube. 2017
https://www.youtube.com/watch?v=uXsiVaAioNk
A different species of Polykrikos (P. hartmannii) capturing prey by retracting its “harpoon”, ingesting various prey species and looking somewhat bulky afterwards:
#Moo Joon Lee, Hae Jin Jeong, Kyung Ha Lee, et al. Mixotrophy in the nematocyst–taeniocyst complex-bearing phototrophic dinoflagellate Polykrikos hartmannii. Harmful Algae. 2015
https://www.researchgate.net/publication/282673410_HA_49_124-134_Polykrikos_hartmannii
A different species of Polykrikos (P. lebourae) after ingesting various prey species:
#Kim, Sunju & Yoon, Jihae & Park, Myung. Obligate mixotrophy of the pigmented dinoflagellate Polykrikos lebourae (Dinophyceae, Dinoflagellata). ALGAE (2015)
“Polykrikos lebourae ingested each prey organism tested in this study. Polykrikos fed Chroomonas sp. 1 (gCR07) (A), Chroomonas sp. 2 (gCR09) (B), Rhodomonas sp. 1 (rCR02) (C), Rhodomonas sp. 2 (rCR04) (D), Rhodomonas sp. 3 (rCR05) (E), Amphidinium sp. (bdAmp01) (F), Heterocapsa sp. (bdHet01) (G), Prorocentrum fukuyoi (bdPF03) (H), and Thecadinium kofoidii (bdTK01) (I) as prey. Scale bars represent: A-I, 20 µm.”
– Now trapped within, the prey is showered in acids that dissolve it alive as it powerlessly struggles to escape.
Many dinoflagellates –, the protist group that Polykrikos belongs to – are able to capture, ingest and digest their prey internally. In such eukaryotic protists that feed by phagocytosis, a main mechanism of digestion is the acidification of intracellular digestive vacuoles by so-called V‑type H⁺‑ATPases: ancient enzymes capable of turning water into acid.
#Yee DP, Samo TJ, Abbriano RM, et al. The V-type ATPase enhances photosynthesis in marine phytoplankton and further links phagocytosis to symbiogenesis. Curr Biol. 2023
https://pmc.ncbi.nlm.nih.gov/articles/PMC10326425/
Quote: “Engulfment of food particles by phagocytosis followed by lysosomal digestion is ubiquitously used by eukaryotic cells,3 protists,47 and invertebrate animals.48 Acidification by VHA [V-type H+-ATPase], which is conserved in all eukaryotes, is essential to these processes.20”
– Just as blood draws more sharks, more and more Polykrikos awake or are attracted and begin killing so mercilessly that they actually contain and then reduce the toxic algae bloom.
Phagotrophic protists – i.e. protists that feed by engulfing other organisms or fragments of tissue –; including dinoflagellates which is the group of protists Polykrikos belongs to, can sense the presence of food and guide their movement towards it. While direct evidence of numerous cells aggregating around prey is not available for Polykrikos, based on contextual evidence from other species it is a reasonable assumption to make that they would engage in this behaviour.
#Jiang H, Kulis DM, Brosnahan ML, Anderson DM. Behavioral and mechanistic characteristics of the predator-prey interaction between the dinoflagellate Dinophysis acuminata and the ciliate Mesodinium rubrum. Harmful Algae. 2018
https://pmc.ncbi.nlm.nih.gov/articles/PMC6089243/
Quote: “•D. acuminata detects its M. rubrum prey via chemoreception at 89 μm mean distance.
•M. rubrum detects D. acuminata via mechanoreception at 41 μm mean distance.
•On detection, D. acuminata approaches M. rubrum with reduced speed.
•M. rubrum responds through long enough escape jumps to detach its chemical trail.
•The desmokont flagellar arrangement of D. acuminata suits itself to phagotrophy.”
#Fenchel T, Blackburn N. Motile chemosensory behaviour of phagotrophic protists: mechanisms for and efficiency in congregating at food patches. Protist. 1999
https://www.sciencedirect.com/science/article/abs/pii/S1434461099700337?via%3Dihub
Quote: “Phagotrophic protists are capable of congregating at point sources of food within a few minutes, from distances of up to several cm in the case of ciliates, or several mm in the case of microflagellates. This is exemplified by four ciliate species and a heterotrophic flagellate. Congregation is accomplished by the combined effect of more than one type of chemosensory motile behaviour including “kinetic responses”, “temporal-gradient sensing”, and “helical klinotaxis”. The results are discussed in terms of microscale patchiness in nature.”
Laboratory evidence suggests that Polykrikos can cause significant killing of Alexandrium and other protists involved in toxic blooms. It is not yet known whether Polykrikos would also reduce or inhibit a large-scale toxic algae bloom in nature.
#Kang HC, Jin Jeong H, So Jin K, et al. Differential feeding by common heterotrophic protists on 12 different Alexandrium species. Harmful Algae. 2018
https://pubmed.ncbi.nlm.nih.gov/30196918/
Quote: “The genus Alexandrium often forms harmful algal blooms causing human illness and large-scale mortality of fish and shellfish. Thus, Alexandrium bloom dynamics are primary concerns for scientists, government officials, aquaculture farmers, and the public. To understand bloom dynamics, mortality due to predation needs to be assessed; however, interactions between many Alexandrium species and their potential predators have not previously been reported. Thus, feeding by five common heterotrophic dinoflagellates (Oxyrrhis marina, Gyrodinium dominans, Polykrikos kofoidii, Pfiesteria piscicida, and Oblea rotunda) and a naked ciliate (Strombidinopsis sp.) on 12 Alexandrium species was examined. Furthermore, the growth and ingestion rates of P. kofoidii on A. minutum CCMP 1888 (previously A. lusitanicum), A. minutum CCMP 113, and A. tamarense were measured as a function of prey concentration. The growth rates of P. kofoidii on the other Alexandrium species at single high prey concentrations were measured, at which the growth rates on A. minutum CCMP 1888 and A. tamarense were saturated. Feeding occurrence by these predators on 12 Alexandrium species could be categorized into 6 different prey groups. Each Alexandrium species was consumed by at least one predator; however, there was no Alexandrium species that was eaten by all six predators. Cells of A. minutum CCMP 1888, A. minutum CCMP 113, and A. tamarense were fed upon by four predators, but A. affine and A. pacificum by only one predator species, P. kofoidii or Strombidinopsis sp. Furthermore, A. minutum CCMP 1888 and A. tamarense supported high growth rates of P. kofoidii, but the other Alexandrium species did not support, but rather inhibited P. kofoidii growth. With increasing prey concentrations, the growth and ingestion rates of P. kofoidii on A. minutum CCMP 1888 and A. tamarense increased and became saturated, whereas those on A. minutum CCMP 113 continuously decreased. The maximum growth rates of P. kofoidii on A. tamarense and A. minutum CCMP 1888 were 1.010 and 0.765 d-1, respectively, and P. kofoidii maximum ingestion rates were 26.2 and 11.1 ng C predator-1d-1, respectively. In contrast, the growth rates of P. kofoidii on the other Alexandrium species at single high prey concentrations were almost zero (A. pacificum) or negative. Based on the feeding occurrence and growth and ingestion rates of predators on 12 Alexandrium species, it is suggested that common heterotrophic protistan predators respond differently to different Alexandrium species, and thus ecological niches of the Alexandrium species may be different from each other. These results may provide an insight into the roles of protistan predators in bloom dynamics of Alexandrium species.”
#Uwe John, Urban Tillmann, Jennifer Hülskötter, et al. Intraspecific facilitation by allelochemical mediated grazing protection within a toxigenic dinoflagellate population. Proc Biol Sci. 2015
https://doi.org/10.1098/rspb.2014.1268
Quote: “Dinoflagellates are a major cause of harmful algal blooms (HABs), with consequences for coastal marine ecosystem functioning and services. Alexandrium fundyense (previously Alexandrium tamarense) is one of the most abundant and widespread toxigenic species in the temperate Northern and Southern Hemisphere and produces paralytic shellfish poisoning toxins as well as lytic allelochemical substances. These bioactive compounds may support the success of A. fundyense and its ability to form blooms. Here we investigate the impact of grazing on monoclonal and mixed set-ups of highly (Alex2) and moderately (Alex4) allelochemically active A. fundyense strains and a non-allelochemically active conspecific (Alex5) by the heterotrophic dinoflagellate Polykrikos kofoidii. While Alex4 and particularly Alex5 were strongly grazed by P. kofoidii when offered alone, both strains grew well in the mixed assemblages (Alex4 + Alex5 and Alex2 + Alex5). Hence, the allelochemical active strains facilitated growth of the non-active strain by protecting the population as a whole against grazing. Based on our results, we argue that facilitation among clonal lineages within a species may partly explain the high genotypic and phenotypic diversity of Alexandrium populations. Populations of Alexandrium may comprise multiple cooperative traits that act in concert with intraspecific facilitation, and hence promote the success of this notorious HAB species.”
#Jeong HJ, Park KH, Kim JS, et al. Reduction in the toxicity of the dinoflagellate Gymnodinium catenatum when fed on by the heterotrophic dinoflagellate Polykrikos kofoidii. Aquat Microb Ecol. (2003)
https://doi.org/10.3354/ame031307
Quote: “To investigate the ability of the heterotrophic dinoflagellate Polykrikos kofoidii to reduce the toxicity produced by the dinoflagellate Gymnodinium catenatum (toxicity = 2.0 to 3.9 Mouse Units [MU]/105G. catenatum cells), we used the mouse bioassay to measure the toxicity retained in a population of P. kofoidii, originally fed G. catenatum for 2 d (ingestion rate = 5.6 cells grazer-1 d-1) and then starved. As a control, we measured the toxicity retained in a population of P. kofoidii originally fed a non-toxic strain of Scrippsiella trochoidea. The toxicity retained in a population of P. kofoidii at Hour 0 (P. kofoidii starved for 0 to 48 h after being fed) was 17.3 MU/105P. kofoidii cells. With increasing elapsed time after starvation the toxicity rapidly decreased to 3.6 MU/105P. kofoidii cells at Hour 24, slowly decreased between Hours 36 and 81, and was not detectable at Hour 96. The decay constant in the exponential equation of the regression line for the toxicity in 105P. kofoidii cells between Hours 0 and 96 was 0.059. No toxicity was detected in P. kofoidii fed S. trochoidea. This evidence suggests that the starvation of P. kofoidii fed G. catenatum may provide dissipation of the toxicity caused by this prey in marine food webs.”
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