[4] There are unique granule filled cells at the base of the cerata that are found nowhere else in the animal that seem to be involved in breaking down connective tissue, as well as two special muscular sphincters.

It is thought that after the connective tissue is broken down, these sphincters contract to cut the cerata and then close the wound.

[1][2][3] M. leonina is the only member of the genus Melibe found on the Pacific coast of North America.

[3] Melibe leonina are common on seagrass and blades of Macrocystis kelp within their range,[3] from the lower intertidal to approximately 37m.

[6] Melibe leonina is a simultaneous hermaphrodite, with its female and male reproductive organs located on the right side of the body.

[7] Both females and males lay eggs in protective ribbons that are secreted from the mucous gland.

[3] While most nudibranchs are predators of sessile benthic organisms, M. leonina feeds on planktonic invertebrates.

Adults feed by pulling back their oral hood until it is almost perpendicular to the body, and then thrust it forward until contact is made with a prey organism.

[9] In aquarium settings, M. leonina have been observed exhibiting different feeding strategies, including surface floating and bottom grazing.

[12] Studies have shown that M. leonina individuals regularly move to other kelp blades, but have rarely been observed swimming during the day in nature.

[3] Experiments in a laboratory setting have supported this theory; showing that on average M. leonina swim 20 times more often at night.