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Phylogeny
Phylogeny
Kingdom: Animalia
Phylum: Cnidaria
Class: Hydrozoa
Order: Siphonophora
Family: Physaliidae
Genus: Physalia
Species: Physalia physalis
Introduction
Introduction
Despite their similar appearance, Portuguese Man o' War are not true jellyfish. Rather, they are a group of colonial animals called siphonophores that belong to the class Hydrozoa, with morphologies that are specialized to the particular function they complete in the colony. These specialized animals are called zooids and may complete a variety of tasks including hunting, feeding, and reproduction. Additionally, Portuguese Man o' War are pleustonic, meaning they float at the interface between water and air through the use of a gas-filled float.
Although these animals have a reputation for their painful and potentially deadly stings, not much is known about their development and drifting dynamics. Furthermore, there may be misconceptions about the severity of the Portuguese Man o' War sting. This website aims to address these issues and inform the reader about the incredible lifestyle of Physalia physalis.
Morphology and Development
Morphology and Development
General Morphology:
General Morphology:
The Portuguese Man o' War is a colony of animals with specialized morphologies designed to accomplish specific tasks. One of these key tasks is keeping the colony at the water's surface. This is accomplished through the use of an animal called the pneumatophore, which is filled with carbon monoxide and air to allow the colony to float. The pneumatophore also acts as a sail to catch the wind and move the colony through the water. This is the only means by which Physalia physalis moves from one location to another as it does not actively move itself. Later in the website, the drifting dynamics of the Portuguese Man o' War will be discussed in greater detail.
In addition to the pneumatophore, there are several other types of zooids which are found in the colony. These include the gastrozooid, gonodendron, and dactylozooid. The gastrozooid is the feeding polyp which consumes food for the colony. This is accomplished through the extracellular digestion of prey, and nutrients are carried to the rest of the colony from the gastrozooids. According to the article by Munro et al., fish and fish larvae comprise of 70%-90% of their diet. This prey is not captured by the gastrozooid itself however, and is instead captured by a zooid specialized for hunting.
The zooid which functions in prey capture is referred to as the dactylozooid, or tentacular palpon (Munro et al.). The tentacular palpon specializes in prey capture because it is responsible for nematocyst production. Nematocysts are the stinging cells which are responsible for the notoriety of the Portuguese Man o' War for their painful stings. These are used to paralyze their prey so that they may be consumed by the gastrozooids. The Portuguese Man o' War has only one type of nematocyst, which is only able to penetrate soft-bodied prey (Munro et al.).
Lastly, the gonodendron is responsible for reproduction. Because Physalia physalis is dioecious, these zooids only contain the gonophores for one sex. The gonodendron is actually a compound structure which contains gonophores, palpons similar to gastrozooids, nectophores that are thought to function in locomotion, and jelly polyps that do not currently have an identified function. The gonodendron is thought to detach from the rest of the colony once it has fully matured, at which time the nectophores may function in propelling the gonodendron through the water (Munro et al.). This phenomenon has not yet been observed, however.
Development:
Development:
Despite knowing the components that make up a Portuguese Man o' War colony, it has been challenging to determine the larval development of Physalia physalis. This is because such development has not been directly observed. However, through use of fixed specimens, Munro et al. described development by comparing the morphology of specimens at different stages in the lifecycle. It was determined that the animal is formed by invagination, with the first zooids being two gastrozooids and a tentacular palpon. Physalia physalis colonies are either left or right handed and is thought to be indicated by the attachment point of the first tentacular palpon. Subsequent budding is determined by the handedness of the colony, which secondary buds appearing on the same side as the tentacular palpon.
Growth is thought to occur in tripartite groups that contain a gastrozooid, a gonodendron, and a tentacular palpon. The gastrozooid and tentacular palpon develop first, with the gonodendron developing and maturing later. Although the colony may look unorganized when observing a mature Portuguese Man o' War, observations of colonies in the juvenile stage display a clear pattern of growth. There are three major axes of growth, which include posterior-anterior growth in the posterior growth zone and posterior and anterior growth in the main zone, secondary buds to the left or right of the original buds along the ventral side, and proximal-distal growth from the ventral side in mature specimens (Munro et al.).
The pneumatophore itself has differing theories as to its ability to release gas during development. Some hypothesize that the pore is completely closed in the larval stage, while others believe that it may not be completely closed but so constricted that gas release is unlikely to occur naturally. Still other reports suggest that juvenile Physalia physalis may be able to release gas, carbon monoxide and air, from the pore. Carbon monoxide is created through aeriform cells, and air is allowed to enter through gas exchange and diffusion.
Drifting Dynamics
Drifting Dynamics
Computations:
Computations:
It was determined in the report by Lee et al. that the drifting dynamics of Physalia physalis are determined by multiple factors including wind speed and direction, ocean currents, the size of the colony, the size and camber of the sail, and the orientation of the sail with respect to the wind, otherwise known as the angle of attack.
Past studies had excluded factors such as the angle of attack, sail camber, and the current. These factors were determined to have a significant impact on the course taken by the colony, however. For instance, the angle of attack was typically determined to be 40 degrees clockwise or counterclockwise depending on the handedness of the colony, which would set a small colony to drift at an angle of approximately 53 degrees from the wind at 2.66% of the speed of the wind. This was consistent with the average size of the bluebottle, to which there is currently debate over whether it is the same species as the Portuguese Man o' War. When using the same conditions with the average size of the Portuguese Man o' War, the drift angle was 51.5 degrees and the speed was 3.73% of that of the wind. This angle did however vary based upon the intensity of the wind speed, which would affect the course of the colony. A greater sail camber was also calculated to impact the angle of attack of the colony and affect the speed of travel. Lastly, the current had a significant affect on the course of the colony as seen in the image below.
Some factors that the authors were unable to include in their study were the influence of the waves, which are currently too complicated to accurately simulate, and variations in the angle of attack for different wind speeds. These are factors that the authors determined would require physical experiments to more accurately model. Furthermore, the drag created by the tentacles was not considered given that this would be highly variable because of its ability to extend and retract, changing its angle and length. This was not believed to significantly affect the calculations for the smaller bluebottle, but would impact the results for the larger Portuguese Man o' War.
Recent Outbreaks:
Recent Outbreaks:
In relation to the drifting dynamics of Physalia physalis, locations in Europe and Brazil have experienced unprecedented numbers of Portuguese Man o' War colonies in past years. With these unexpected swarms, many have scrambled to determine if these swarms are to be expected in the future or if they were simply a freak occurrence resulting from unusual wind and current conditions.
One article describes unusual swarms of Physalia physalis in the Mediterranean, which resulted in the fatality of one woman in Sardinia (Prieto et al.). Recognizing the potential impact the movement of Physalia physalis into the Mediterranean could have on the tourism industry in the area, the authors were motivated to determine if such swarms could be predicted in the future. They used mathematical models to simulate the swarms seen that year and used it to determine if this situation was to be expected in following years.
From the calculations, it was determined that the sudden invasion of Physalia physalis into the Mediterranean was likely the result of unique climatic conditions from the previous winter and was unlikely to be a repeated occurrence in the future. This could likely explain the unusual beachings in Brazil and other parts of Europe as well.
Envenomation
Envenomation
Introduction:
Introduction:
Portuguese Man o' War are notorious for their painful and potentially life-threatening stings. However, one must consider whether this notoriety is warranted or whether it has become overblown in a way reminiscent of the terror that struck the public after the creation of the movie Jaws, which led to the mass hunting of sharks. The Mediterranean basin experienced its first human fatality from a jellyfish sting during the 2010 invasion of Physalia physalis (Prieto et al.). This fatality was the result of an allergic reaction to the Portuguese Man o' War sting, however; and it begs the question as to whether such severe reactions are normal with Physalia physalis stings. This section utilizes articles from two different areas to analyze the reactions to Physalia physalis stings and their response to medical treatment.
Brazil:
Brazil:
According to Haddad et al., the discharge of cnidae in Physalia physalis is a result of mechanical and chemical stimuli. When an individual is stung by these cnidae, they can experience local symptoms such as intense pain and a burning sensation. More extreme reactions can result in vomiting, nausea, arterial hypotension, seizures, cardiac arrhythmias, respiratory failure, and death. To observe the most commonly expressed symptoms and their reactions to treatment, 331 patients were examined over a period of 4 days, with follow-up questionnaires sent out 2 years after the incident.
Patients were all observed to show the same local signs of extremely painful linear plaques of variable length and skin lesions that presented in a characteristic rosary-like pattern. Cold sweats were the most common systemic manifestation (16.3%), followed by vomiting/nausea (9.9%) and tachychardia (7.2%). Chest pain and arterial hypotension were only present in 0.9% of patients.
Recommended treatment included vinegar baths and cold marine water compresses and was accepted by 84.2% of the patients. Of the remaining patients, 14.8% arrived at the hospital without pain and dismissed treatment, while 0.9% refused any treatment. All patients initially reported severe pain. Using the information collected from the questionnaires, it was determined that, of the 124 responses, 12.9% of patients reported late clinical symptoms with local persistence of pigmentation being the most common (8.8%).
In conclusion of the study, the authors of the article determined that most symptoms were not severe and were restricted to local symptoms. It was noted that the pain disappeared for 88.5% of patients within 3 hours, but could last up to 24 hours if not treated. The recommended treatments were observed to be largely successful.
France:
France:
In another article by Labadie et al., victims of Physalia physalis stings were observed along the Aquitaine Coast of France. In this study, both symptoms and treatments appeared to present themselves slightly differently despite being the same species as the ones observed in Brazil. The study examined 40 cases in 2008, 154 cases in 2010, and 885 cases in 2011.
It was observed that most cases resulted in lesions that progress to local skin necrosis within 24 hours, resulting in the formation of multiple scab wounds. These scabs would disappear in two weeks, leaving behind a scar that would last for a prolonged period or become permanent. The general symptoms recorded include abdominal pain, vomiting, aching, cramps, and spasms. In the most severe cases, drowsiness, diffuse sweating, confusion, fainting, dyspnea, and precordialgia were reported. Six-month follow-up appointments indicated that approximately 30% of the patients still displayed definitive dermal marks and pigmented scars from the incidents.
To treat the patients, the stings were liberally rinsed with seawater, and tentacles were removed with shaving cream. Symptomatic cases were then also treated with painkillers, corticoisteroids, and/or anxiolytic drugs. Vinegar application was controversial at the time of the study and was therefore not used.
This study noted that the appearance of Physalia physalis was unusually high in these years, and the reason for this had not yet been determined. However, this corresponds rather closely with the massive swarms that appeared in the Mediterranean basin; and the swarms observed in this study may be the result of the reasons found for the swarms detailed in the other article.
References
References
Peer Reviewed Sources:
Munro, Catriona, et al. "Morphology and development of the Portuguese man of war, Physalia physalis." Scientific Reports, 2019
Lee, Daniel, et al. "Drifting dynamics of the bluebottle (Physalia physalis)." Ocean Science, 1 Oct. 2021, pp. 1341-1351.
Prieto, L. et al. "Portuguese Man-of-War (Physalia physalis) in the Mediterranean: A permanent invasion or a casual appearance?" Scientific Reports, 25 June 2015
Haddad, Vidal, et al. "An outbreak of Portuguese man-of-war (Physalia physalis - Linnaeus, 1758) envenoming in Southeastern Brazil." Revista da Sociedade Brasiliera de Medicina Tropical, Sept. 2013, pp. 641-644.
Labadie, Magali, et al. " Portuguese man-of-war (Physalia physalis) envenomation on the Aquitaine Coast of France: An emerging health risk." Clinical Toxicology, 2012, pp. 567-570.
Images Sources:
https://animals.howstuffworks.com/marine-life/portuguese-man-of-war.htm
https://wiki.nus.edu.sg/display/TAX/Physalia+physalis+-+Portuguese+Man-of-War
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