This is a Daphnia ssp., more commonly known as a water flea. It lives in ponds in North America, but it can sometimes be found in marine environments as well (Britannica 1999).

 Primary Literature Article: “Effects of Cell-Bound Microcystins on Survival and Feeding of Daphnia spp.” (Rohrlack et al. 2001) 

Kingdom: Animilia (Ebert 2005)

Phylum: Arthopoda

Subphylum: Crustacea

Class: Branchiopoda

Order: Diplostraca

Suborder: Cladocera

Family: Daphniidae

Genus: Dapnia

Species: Daphnia ssp.

This multicellular organism consumes organic material across the ponds and streams of North America. It is often eaten by many fish or other freshwater creatures that are larger than its size (.2-3mm) (Britannica 1999).

 They don't have many defense mechanisms, but they can move around in the water by stroking their antennae. It is said to look like a hopping motion rather than a smooth stroke (Britannica 1999).

 They are typically filter feeders, but some water fleas like to attach themselves to plants or feed off the bottom of ponds or streams. They use leaf-like legs to create a current in the water that places the organic material in their bodies (Britannica 1999).

For the majority of the time, the female water flea reproduces A-sexually, as she grows eggs in her body, and can hatch them as early as 3 days later. But as they get older, they may begin to have their eggs fertilized by a male water flea. This process is called cyclical parthenogenesis (Ebert 2005).

Microcystis: A genus of freshwater cyanobacteria that can consist of harmful algal blooms. They produce a harmful toxin called microcystin that affects the digestion and feeding of Daphnia ssp. (Rohrlack et al. 2001).

 In the primary literature article, they tested the Daphnia's digestion against these types of bacteria to see if they had harmful effects (Rohrlack et al. 2001). 

Strain PCC7806: the type of genetically modified mycrotosin used in the experiment (Rohrlack et al. 2001).

Summary: The study looked at how the ingestion of Microcystis affects the survival rates of Daphnia spp. They compared 2 types of these cyanobacteria: one that had Microcystis, and one that was genetically made in a lab to not have Microcystis (Rohrlack et al. 2001). 

Results: The toxin microcystin that was in microcystin harmed all of the Daphnia ssp. (Rohrlack et al. 2001). The time it took for the organism to die was closely related to the amount of microcystin ingested. Also, the Daphnia slowed down its ingestion of BOTH types of algae (the natural microcystin and the genetically modified one) meaning that it couldn't detect which type of algae contained the toxin (Rohrlack et al. 2001).

 Conclusion: The survival time was correlated with the amount of microcystin consumed, rather than the sensitivity to the toxin itself (Rohrlack et al. 2001). They were able to form a mathematical formula to show the relation between the survival time and the microcystin ingestion rate (Rohrlack et al. 2001). 

Overall, the Daphnia ssp. is sensitive to microcystin in the mircocystis algae, but it does not have the ability to detect whether or not the toxin is in the algae, so it tries to stay away from it more often (Rohrlack et al. 2001).

 Why is this important? 

Understanding how these harmful toxins affect the Daphnia ssp. can help us understand how they may affect the rest of the coastal marine ecosystem, as they are at the bottom of the food chain and are food to many types of fish. Also, there is a risk of a toxin transfer up the food chain if the Daphnia ssp. eat the toxin, fish eat the Daphnia ssp., and then humans eat the fish. It brought awareness to the harmful possibilities of the eating habits of the Daphnia ssp.