Comprehensive Description

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Biology/Natural History: This nudibranch is unusual in several ways. It lacks a radula, but its oral veil is expanded hugely into a hood which it extends ahead of itself and uses to trap small crustaceans and other prey. Its diet includes copepods, amphipods, and ostracods, as well as small post-larval mollusks. The animal stands attached to the substrate (often a blade of eelgrass) and expands the oral hood. It then sweeps the hood left and right or downward (photo). When the ventral surface of the hood contacts a small animal the hood rapidly closes and the fringing tentacles overlap, holding the prey in. The whole animal is then forced into the nudibranch's mouth. Predators include the kelp crab Pugettia producta. Pycnopodia helianthoides is repelled from contact. The polychaete scaleworm Halosydna brevisetosa is sometimes a symbiont, feeding on fecal pellets. Some may have symbiotic algae.

Branches of the gut extend out into the cerata. The name is due to the large hood which may look like a lion's mane.

This species hunts mainly attached, but is a good swimmer (movie). When swimming it is usually upside-down, and thrashes or undulates back and forth. It is often seen swimming near the water's surface in the summer (movie), or after fall and winter storms disturb the eelgrass. Eggs are laid in long, wide yellow or cream-colored ribbons in the summer, which are attached to kelp and eelgrass. The ribbons form tight coils or wavy folds. Eggs can be found in the Washington area at any season. They appear to live about one year, reciprocally fertilize one another (as with most nudibranchs they are hermaphrodites), lay their eggs and die. This species has been used for neurological research.


Creative Commons Attribution Non Commercial Share Alike 2.0 (CC BY-NC-SA 2.0)

© Rosario Beach Marine Laboratory

Source: Invertebrates of the Salish Sea

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