Aplysiidae is the only family in the superfamily

Aplysioidea Aplysioidea is a Taxonomic rank, superfamily of predatory sea snails, marine (ocean), marine gastropod Mollusc, mollusks within the clade Anaspidea.Gofas, S. (2010). Akeroidea. In: MolluscaBase (2017). Accessed through: World Register of Marine S ...

, within the clade Anaspidea. These animals are commonly called sea hares because, unlike most

sea slugs Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time ...

, they are often quite large, and when they are underwater, their rounded body shape and the long

rhinophores A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea ha ...

on their heads mean that their overall shape resembles that of a sitting rabbit or hare. Sea hares are however sea snails with shells reduced to a small plate hidden between the parapodia, and some species are extremely large. The Californian black sea hare, ''

Aplysia vaccaria ''Aplysia vaccaria'', also known as the black sea hare and California black sea hare, is a species of extremely large sea slug, a marine, opisthobranch, gastropod mollusk in the family Aplysiidae.Bouchet, P. (2011). Aplysia vaccaria Winkler, ...

'' is arguably the largest living gastropod species, and is certainly the largest living

heterobranch Heterobranchia, the ''heterobranchs'' (meaning "different-gilled snails"), is a taxonomic clade of snails and slugs, which includes marine, aquatic and terrestrial gastropod mollusks. Heterobranchia is one of the main clades of gastropods. Cur ...

gastropod.

Description

Members of the Aplysiidae have an atrophied inner shell (in contrast with the

nudibranch Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, ...

s, which have no shell at all). In ''Aplysia'' and ''Syphonota'', this shell is a soft flattened plate over the

visceral In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...

rear end, where it is fully or partially enclosed in the mantle skin. In ''Dolabella auricularia'', the shell is ear-shaped. The shell is only present in the larval stage of the two genera '' Bursatella'' and ''Stylocheilus'', and on this basis they have been grouped into the subfamily Dolabriferinae. They are rather large animals. Their length can reach up to 75 cm (''Aplysia vaccaria''), and they can weigh well over 2 kg. They are

cosmopolitan Cosmopolitan may refer to: Food and drink * Cosmopolitan (cocktail), also known as a "Cosmo" History * Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953 Hotels and resorts * Cosmopoli ...

and found in temperate and tropical seas, inhabiting shallow coastal areas and sheltered bays, thick with vegetation. The Aplysiidae are

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

, eating a variety of red, green or brown

alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

e and

eelgrass Eelgrass is a common name for several plants and may refer to: * ''Zostera'', marine eelgrass * ''Vallisneria'', freshwater eelgrass {{Short pages monitor