Siphonophores are carnivorous animals part of the phylum Cnidaria, which also includes sea anemones, jellyfish and corals. Most siphonophores are active swimmers that spend majority of their time in the deep sea. A specific siphonophore is a colonial jellyfish called Marrus orthocanna.

Marrus orthocanna – credit google images


Morphology and movement

It appears like a “rocket” with a main body and then tentacles extending from the bottom. Its main body is comprised of multiple bells arising from the main stem.Along the protozooid are nectophores, these are jar like shapes that structure M. orthocanna. These jar shapes have a red/ orange lining which is its food canal that the entire colony of nectophores share.

Marrus orthocanna can have a colony that exceeds between 1 to 2 meters and its nectosome can extend up to 10cm.

The colonial jellyfish moves as a colony by the nectophores contracting and propelling in any direction chosen. It has a small yellow orange pneumatophore, a gas filled float, at the top that makes sure it does not sink to the bottom.


Marrus orthocanna bell structure – photo credit Kevin Raskoff

How and what does is eat?

It is an ambush predator that feeds on copepods, decapods (groups of small crustaceans)  and rarely small fish. The zooids of the colony are feeding polyps, they feed by capturing food using its mouth: a single long tentacle. This is done by extending the tentacle and tentilla (nematocysts) into the water to create a transparent net. To bring the prey in once being trapped by the filament (chain of protein) contracts and the cnidae (an explosive cell).


M. orthocanna lives in the deep sea at depths ranging between 200 and 800 meters, it has even been found at depths of 2000 meters. The unusual looking siphonophore occurs pelagically in open waters in the Arctic Ocean, northwest Pacific Ocean, North Atlantic Ocean and Mediterranean Sea.


These jellyfish have have reproductive structures located in the siphosome, area that contains feeding, reproductive and defensive zooids. The eggs and sperm mature in specialized medusae (a free swimming form). Some siphonophores have male and female structures in the same colony and others have both sexes separate.


Although M. orthocanna may have a fragile gelatinous body however it has learn’t to survive the extreme cold temperatures, high pressure and minimal food source availability. It has done this by being able to capitalize on its swimming capability and it spread it tentacles widely to have a greater chance at catching prey.

Fun fact

Submarines in World War II were able to hide from the enemy’s sonar using a large group of siphonophores, this is because the sonar waves could be scattered by the siphonophores soft bodies.


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