The sea bunny has gained significant online attention due to its charming appearance. Its fluffy body and ear-like appendages often lead to a common question: are sea bunnies really slugs? This article clarifies their true classification.
Unpacking the “Sea Bunny” Name
The “sea bunny” name is descriptive, stemming from its physical resemblance to a rabbit. The most recognized species, Jorunna parva, has two distinctive structures mimicking a bunny’s ears and tail. The prominent “ears” are chemosensory organs called rhinophores, which detect chemical signals in the water. These rhinophores are often fuzzy, increasing their surface area for reception.
At the posterior end, a cluster of feathery structures resembles a fluffy “tail.” This is the branchial plume, which functions as the animal’s gills for respiration. The “furry” appearance is not actual fur, but a covering of small rod-like structures called caryophyllidia, interspersed with tiny black specks. These caryophyllidia are believed to play a sensory role.
The Slug Connection
Sea bunnies are a type of sea slug. They belong to a group of marine gastropod mollusks known as nudibranchs. The term “nudibranch” translates to “naked gills,” referring to exposed gill structures like the branchial plume. Unlike land slugs, sea slugs are exclusively marine and possess unique adaptations for their underwater existence.
Sea bunnies (Jorunna parva) are classified within the family Discodorididae, part of the order Nudibranchia. Nudibranchs are soft-bodied and lack a shell as adults, differentiating them from many other mollusks. They start life with a shell during their larval stage, shedding this protective layer through metamorphosis as they mature.
Life Under the Sea
Sea bunnies inhabit the Indo-Pacific Ocean, with populations in diverse locations including Japan, the Philippines, Papua New Guinea, and parts of the Indian Ocean. These tiny creatures, typically less than an inch long, are benthic, meaning they live on or near the seafloor. They thrive in areas with abundant food sources, often on rocks or marine vegetation.
Their diet primarily consists of marine sponges. Sea bunnies use a specialized feeding organ called a radula, a ribbon-like structure with tiny teeth, to scrape food from surfaces. They absorb toxins from their sponge prey, storing them in their bodies for defense against predators. This sequestration of toxins makes sea bunnies unpalatable to most potential threats.