This fascinating carnivorous sea slug is called a melibe leonina, a lion’s mane sea slug, or a hooded nudibranch. The ‘hood’ refers to its large mouth that expands like a net to trap at small crustaceans and mollusks, jellyfish and ctenophores, amphipods, copepods, and more.
This nudibranch is up to 102 mm long, 25 mm wide, and 51 mm across the expanded oral hood.
The body of this nudibranch is translucent. It is usually colorless to pale yellow or green, with opaque brown hepatic diverticula. It has a large expandable oral hood, fringed with sensory tentacles, which it opens and throws forward in order to catch food. A single pair of rhinophores on the hood are rounded and earlike. 4-6 pairs of flat paddle shaped cerata run along its dorsum in two rows.
Melibe leonina exudes a sweet fruity aroma when it is removed from the water, or when numerous individuals are kept together in captivity. Because of their smell and the way they expand their oral hoods while attached to kelp and eelgrass, a group of Melibe is called a “bouquet”.
h/t Katie Mack.