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 by D. Young, photos by D. Young and Cara Mackenzie