The Jorunna parva, affectionately nicknamed the sea bunny, is a small marine gastropod that captured global attention due to its striking resemblance to a fuzzy rabbit. This tiny creature is often spotted with two prominent “ears” and a fluffy body, leading many to wonder how it navigates the underwater world. Understanding how this slug perceives its environment reveals a sophisticated reliance on senses other than sight.
Identifying the Sea Bunny: A Type of Nudibranch
The sea bunny is not a true rabbit but a species of dorid nudibranch, a type of shell-less marine mollusk commonly referred to as a sea slug. Adult individuals are remarkably small, typically measuring less than one inch long (about 2.5 centimeters). The creature’s signature fluffy appearance is not fur but an outer covering of sensory organs known as caryophyllidia. These tiny, fleshy rods cover its mantle and are often interspersed with black specks, giving the Jorunna parva its soft, spotted look and contributing to its sensory perception.
Visual Perception: The Location and Function of Their Eyes
The central question of whether sea bunnies have eyes is answered with a subtle “yes,” though their vision is extremely limited. Like other dorid nudibranchs, the sea bunny possesses a pair of simple eyes known as ocelli. These minute, dark spheres are deeply embedded within the slug’s skin, typically located near the base of the rhinophores. Because of their simple structure, the ocelli cannot form detailed images. Their function is primarily restricted to sensing light intensity and detecting shadows. This rudimentary vision allows the sea bunny to distinguish between light and dark, which helps detect the shadow of an overhead predator or regulate its internal body clock.
Sensing the Environment: The Role of External Sensory Organs
Since their vision is poor, the sea bunny relies heavily on chemosensory and tactile organs for navigation and survival. The two conspicuous “ears” are highly specialized chemosensory structures called rhinophores. These club-like organs are covered in fine folds that significantly increase the surface area available to detect minute chemical gradients in the water. The rhinophores function much like an underwater nose, allowing the slug to “smell” dissolved chemicals to locate a food source or a potential mate over large distances. The sea bunny also uses its oral tentacles, which are small, tapering feelers situated on either side of its mouth. These tentacles are primarily used for tactile sensing, helping the slug feel its way along the substrate, and they also taste the surface to confirm the presence of food.
Diet and Habitat
The Jorunna parva inhabits the tropical and subtropical waters of the Indo-Pacific Ocean, with notable sightings off the coasts of Japan, the Philippines, and Australia. They are benthic creatures, meaning they live on the sea floor, often in shallow coastal areas. The sea bunny is a specialist predator, feeding almost exclusively on sponges, particularly those belonging to the family Chalinidae. By consuming these toxic sponges, the nudibranch sequesters the ingested toxins and stores them in its own tissues for defense. This chemical defense mechanism makes the sea bunny an unappealing meal for most potential predators.