Hi there! Thanks for asking! I’ve actually never seen this one before and boy is it weird haha
The Melibe viridis is a predatory nudibranch, or type of sea slug that’s got some interesting adaptations to search for and catch its food.
There is in all of its glory. In the front you have its “oral veil” that acts like a net. It scans the sea floor for small fish and crustaceans. When something brushes the sensitive papillae along the edge of the veil, it quickly closes to trap and eat its prey (kind of similar to how a venous fly trap works).
This video shows one going after a little frog fish. It also looks like these sea slugs can swim for short bursts if necessary but they are going to be primarily benthic species (living on the sea floor). The Melibe viridis has also adapted to blend in with its environment, you can actually see in this video that the sea slug and the frog fish have similar colors and textures since they are living in the same environment.
Thanks again for bringing this stunning animal to my attention. I’m so glad you are enjoying the blog!