Aplysiidae
Encyclopedia
The superfamily
Aplysioidea is a superfamily of mostly rather large sea slug
s, marine gastropod mollusks in the clade
Aplysiomorpha within the informal group Opisthobranchia
.
This superfamily contains only one family
, the Aplysiidae; the sea hare
s. These animals are commonly called sea hares because, unlike most sea slugs, they are often quite large, and when they are underwater, their rounded body shape and the long rhinophores on their heads mean that their overall shape resembles that of a sitting rabbit or hare
.
Sea hares are however shell-less sea snail
s, and some species are extremely large. The Californian black sea hare, Aplysia vaccaria
is arguably the largest living gastropod species, and is certainly the largest living shell-less gastropod.
In Australia
sea hares are sometimes known as "beach blobbies". Sea hares do sometimes become stranded on beaches, and when this happens, they contract as much as possible to minimize desiccation, and when the sea hare's body is not fully supported by water, the rhinophores collapse and the animal looks more blob-like.
s, which have no shell at all). In Aplysia and Syphonota, this shell is a soft flattened plate over the visceral 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 varies between 20 cm and 75 cm (Aplysia vaccaria), and they can weigh well over 2 kg. They are cosmopolitan
and found in temperate and tropical seas, inhabiting shallow coastal areas and sheltered bays, thick with vegetation.
The Aplysiidae are herbivorous
, eating a variety of red, green or brown algae and eelgrass
. Their color is diet-derived from the pigments of the algae. They concentrate the toxins found on algae.
Sea hares have two main secretory glands in their mantle cavity.
The genus Aplysia
has proved useful as a model in neurobiology for the study of electrical synapse
s, which mediate the release of the clouds of ink (Kandel et al., 2000).
s, with fully functional male and female reproductive organs.
The penis
is on the right side of the head while the vagina
is situated in the mantle cavity, beneath the shell, deep down between the parapodia. It is therefore physically impossible for mating partners to act as both male and female at the same time.
They have unusual mating habits: they can mate in pairs with one acting as a male, the other as a female, but they commonly occur in quite crowded numbers during the mating season, and this often leads to chains of three or more sea hares mating together. The one at the front acts as a female and the one at the back as a male. The animal(s) in between are acting as both males and females, in other words, the animal receiving sperm passes its own sperm to a third sea hare.
, wrasse
s and sea turtle
s.
The authority of this family is still somewhat in dispute. The family was incorrectly originally spelled as Laplysiana. This was a Latinized form of the original common name "les Laplysiens" as described in Philosophie zoologique, 1:320 by Lamarck
in 1809. Rafinesque introduced the new name Laplysinia in 1815. In 2001 Bouchet & Rocroi advocated the attribution of the name Aplysiidae to Lamarck.
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
Aplysioidea is a superfamily of mostly rather large sea slug
Slug
Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
s, marine gastropod mollusks in the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Aplysiomorpha within the informal group Opisthobranchia
Opisthobranchia
Opisthobranchs are a large and diverse group of specialized complex marine gastropods previously united under Opisthobranchia within the Heterobranchia, but no longer considered to represent a monophyletic grouping...
.
This superfamily contains only one family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
, the Aplysiidae; the sea hare
Sea hare
The clade Aplysiomorpha, commonly known as Sea hares or Sea Bags , are medium-sized to very large Opisthobranchia with a soft internal shell made of protein...
s. These animals are commonly called sea hares because, unlike most sea slugs, they are often quite large, and when they are underwater, their rounded body shape and the long rhinophores on their heads mean that their overall shape resembles that of a sitting rabbit or hare
Hare
Hares and jackrabbits are leporids belonging to the genus Lepus. Hares less than one year old are called leverets. Four species commonly known as types of hare are classified outside of Lepus: the hispid hare , and three species known as red rock hares .Hares are very fast-moving...
.
Sea hares are however shell-less sea snail
Sea snail
Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....
s, and some species are extremely large. The Californian black sea hare, Aplysia vaccaria
Aplysia vaccaria
Aplysia vaccaria, also known as the "black sea hare," and the "California black sea hare," is a species of extremely large sea slug, a marine, opisthobranch, gastropod mollusk in the family Aplysiidae. It is the largest known species of sea slug, and may be the world's largest living gastropod. -...
is arguably the largest living gastropod species, and is certainly the largest living shell-less gastropod.
In Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
sea hares are sometimes known as "beach blobbies". Sea hares do sometimes become stranded on beaches, and when this happens, they contract as much as possible to minimize desiccation, and when the sea hare's body is not fully supported by water, the rhinophores collapse and the animal looks more blob-like.
Description
Members of the Aplysiidae have an atrophied inner shell (in contrast with the nudibranchNudibranch
A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...
s, which have no shell at all). In Aplysia and Syphonota, this shell is a soft flattened plate over the visceral rear end, where it is fully or partially enclosed in the mantle
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
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 varies between 20 cm and 75 cm (Aplysia vaccaria), and they can weigh well over 2 kg. They are cosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
and found in temperate and tropical seas, inhabiting shallow coastal areas and sheltered bays, thick with vegetation.
The Aplysiidae are herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, eating a variety of red, green or brown algae and eelgrass
Seagrass
Seagrasses are flowering plants from one of four plant families , all in the order Alismatales , which grow in marine, fully saline environments.-Ecology:...
. Their color is diet-derived from the pigments of the algae. They concentrate the toxins found on algae.
Defenses
Some species spout ink when disturbed or attacked, and they may also swim (rather than crawl) away, using their broad wing-like flaps or parapodia. The ink is extracted from their algal food, rather than being synthesized.Sea hares have two main secretory glands in their mantle cavity.
- purple gland: lying on top of the mantle cavity, above the gill. It gives off a red or purple fluid, or, in some species, a white ink.
- opaline gland: situated on the floor of the mantle cavity, beneath the gill. It gives off a white opaque secretion.
The genus Aplysia
Aplysia
Aplysia is a genus of medium-sized to extremely large sea slugs, specifically sea hares, which are one clade of large sea slugs, marine gastropod mollusks. The general description of sea hares can be found in the article on the superfamily Aplysioidea....
has proved useful as a model in neurobiology for the study of electrical synapse
Electrical synapse
An electrical synapse is a mechanical and electrically conductive link between two abutting neurons that is formed at a narrow gap between the pre- and postsynaptic neurons known as a gap junction. At gap junctions, such cells approach within about 3.5 nm of each other, a much shorter...
s, which mediate the release of the clouds of ink (Kandel et al., 2000).
Mating habits
Sea hares are hermaphroditeHermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
s, with fully functional male and female reproductive organs.
The penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
is on the right side of the head while the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
is situated in the mantle cavity, beneath the shell, deep down between the parapodia. It is therefore physically impossible for mating partners to act as both male and female at the same time.
They have unusual mating habits: they can mate in pairs with one acting as a male, the other as a female, but they commonly occur in quite crowded numbers during the mating season, and this often leads to chains of three or more sea hares mating together. The one at the front acts as a female and the one at the back as a male. The animal(s) in between are acting as both males and females, in other words, the animal receiving sperm passes its own sperm to a third sea hare.
Predators
Predators include pycnogonid sea spidersSea spider
Sea spiders, also called Pantopoda or pycnogonids, are marine arthropods of class Pycnogonida. They are cosmopolitan, found especially in the Mediterranean and Caribbean Seas, as well as the Arctic and Antarctic Oceans. There are over 1300 known species, ranging in size from to over in some deep...
, wrasse
Wrasse
The wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 82 genera, which are divided into nine subgroups or tribes....
s and sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...
s.
Taxonomy
A 2004 study has shown that Aplysiidae is a monophyletic taxon with two distinct clades: Aplysiinae and Dolabellinae + Dolabriferinae + Notarchinae.The authority of this family is still somewhat in dispute. The family was incorrectly originally spelled as Laplysiana. This was a Latinized form of the original common name "les Laplysiens" as described in Philosophie zoologique, 1:320 by Lamarck
Jean-Baptiste Lamarck
Jean-Baptiste Pierre Antoine de Monet, Chevalier de la Marck , often known simply as Lamarck, was a French naturalist...
in 1809. Rafinesque introduced the new name Laplysinia in 1815. In 2001 Bouchet & Rocroi advocated the attribution of the name Aplysiidae to Lamarck.
Subfamilies
Classification after N. B. Eales (1984):- Aplysiinae Lamarck, 1809
- Dolabellinae Pilsbry, 1895
- Dolabriferinae Pilsbry, 1895
- Notarchinae Mazzarelli, 1893
Genera
- AplysiaAplysiaAplysia is a genus of medium-sized to extremely large sea slugs, specifically sea hares, which are one clade of large sea slugs, marine gastropod mollusks. The general description of sea hares can be found in the article on the superfamily Aplysioidea....
Linnaeus, 1767 - type genus - BursatellaBursatellaBursatella leachii, common name the ragged sea hare or shaggy sea hare, is a species of large sea slug or sea hare, a marine gastropod mollusk in the family Aplysiidae, the sea hares.-Distribution:...
Blainville, 1817 - the only one species: Bursatella leachii Blainville, 1817 - Dolabella Lamarck, 1801
- DolabriferaDolabriferaDolabrifera is a genus of sea hares, a taxonomic group of sea slugs or marine opisthobranch gastropod mollusks belonging to the family Aplysiidae.-Species:Species within the genus Dolabrifera include:* Dolabrifera ascifera...
Gray, 1847 - NotarchusNotarchusNotarchus is a genus of sea slugs or sea hares, marine opisthobranch gastropod mollusks in the family Aplysiidae, the sea hares.-Description:...
Cuvier, 1817 - PetaliferaPetaliferaPetalifera is a genus of sea slugs or sea hares, marine gastropod mollusks belonging to the family Aplysiidae, the sea hares.Some authors place this genus in a separate family Dolabriferidae...
Gray, 1847 - PhyllaplysiaPhyllaplysiaPhyllaplysia is a genus of sea slugs, specifically sea hares, marine gastropod mollusks in the family Aplysiidae, the sea hares.Some authors place this genus in a separate family, Dolabriferidae.-Species:...
Fischer, 1872 - SyphonotaSyphonotaSyphonota geographica, or the geographic sea hare, is a species of sea slug or sea hare, a marine opisthobranch gastropod mollusk in the family Aplysiidae, the sea hares....
H. Adams & A. Adams, 1854 - the only one species: Syphonota geographica (A. Adams & Reeve, 1850) - StylocheilusStylocheilusStylocheilus is a genus of sea slugs, specifically sea hares, marine opisthobranch gastropod mollusks in the family Aplysiidae, the sea hares.According to some authors this genus belongs in the family Dolabriferidae....
Gould, 1852