Ctenophore (comb jellyfish) Larva – Cyddipid Larva
February 19, 2013 Plankton Tow – Cadboro Bay
Unidentified Larva – Likely a Cydippid (ctenophore) Larva
Beroid Comb Jelly (Beroe abyssicola)
Common name: Beroid Comb Jelly
Scientific name: Beroe abyssicola
Size range: up to 7 centimetres
Beroe abyssicola has a cylindrical shape with rounded ends, they bear eight evenly spaced rows of cilia or “combs” which they beat in waves for locomotion. the comb rows stop just before the oral end where a mouth, resembling a pair of lips, is located. Their most distinguishing characteristics are their translucent, pinkish red colouration through which their more intensely coloured pharynx is visible, as well as their complete lack of tentacles.
They inhabit the waters of the North Pacific at an average depth of 1028-1840 metres. They will occasionally come to the surface, however they may lose their pinkish colouring in the process.
Beroe abyssicola is a carnivorous predator that swims, hunting for prey, with its mouth closed for a more streamlined shape. when it encounters prey, of which it prefers other ctenophores, it can open its mouth to quickly engulf its prey. It can even swallow other ctenophores larger than itself, or bite pieces off with its fused cilia, called macrocilia that line the inside of its mouth and function as simple teeth.
Not much is known about what exactly preys upon Beroe abyssicola, but the most likely predators are other ctenophores, jellyfish and other animals like fish and sea turtles.
Beroe abyssicola is a hermaphroditic species, meaning that it has both female and male gonads. As a result it is thought to be able to occasionally fertilize its own eggs. Regardless it will eject its sperm and/or eggs directly from the mouth into the open water where the eggs are fertilized externally. After fertilization the eggs will go through a larval stage, resembling a smaller adult, that will grow into a full adult. Throughout the life cycle it will remain part of the phytoplankton and is therefore considered holoplanktonic.
Beroe abyssicola does not have a very complex nervous system; it has a loose net of nerves spanning its body called a nerve net that may be more concentrated near sensory organs. Because of its simple nerve network it is limited to simple behaviors, such as swimming and navigating for prey, maneuvering away from obstacles and feeding on located prey, which it is able to sense with chemo receptors.
Photographs and Video by Adam Kitzler and D. Young
All gooseberries are hermaphrodites and reproduce sexually. Fertilization takes place externally and the resulting larvae (known as cydippid larva) are free swimming. Most gooseberries die after spawning. The Sea Gooseberry is planktonic its entire life, and there is no sessile stage. Once a larva has become a fully grown gooseberry, it is capable of releasing up to 1000 eggs per day. Gametes are released into the ocean via the gonopores, located on the comb-rows. The average lifespan of the Sea Gooseberry is 4.6 Months (140.01 days).
P. bachei hunt by extending their two long tentacles behind them and swimming through the water column. As the tentacles touch their prey, they become stuck to the specialized sticky cells on the tentacles called “colloblasts”. Once the prey is stuck, the gooseberry spins to wrap its tentacles around itself so that it can take the food trapped in its tentacles into its mouth. The P. bachei kept in our school aquarium feed upon newly hatched live brine shrimp (Artemia sp.). Unlike P. bachei, other gooseberry species such as the Beroid Gooseberry (Beroe abbysicola) are aggressive ambush predators that hunt without using tentacles. They primarily eat copepods and krill, but also eat fish eggs, mollusks, small crustaceans, larvae, and even other gooseberries.
The P. bachei is often preyed upon by large jellyfish such as Aurelia aurita and A. labiata. It is also eaten by fish like salmon and sometimes sea turtles. They can only escape from predators by beating the cilia in their comb-rows, and are the largest animals in the world to move through the use of cilia.
Video 1 by D. Young
Video 2 “Sea Gooseberry – close up” by Saidi, Hanna and Marijke
photos by D. Young and Cara Mackenzie
Interesting resources for research and photographer credit
Victoria High School
1260 Grant St.
Victoria. BC, Canada