Aplysia is a genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of medium-sized to extremely large sea 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, specifically 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, which are one 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...

 of large sea slug
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...

s, marine
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

 gastropod mollusks. The general description of sea hares can be found in the article on the superfamily Aplysioidea.

These benthic herbivorous sea hares can become rather large compared with most other mollusks. They graze in tidal and subtidal zones of tropical waters, mostly in the Indo-Pacific Ocean (23 species); but they can also be found in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 (12 species), with a few species occurring in the Mediterranean.

Aplysia species, when threatened, mostly release clouds of ink to blind the attacker. Following the lead of Eric R. Kandel
Eric R. Kandel
Eric Richard Kandel is an American neuropsychiatrist who was a recipient of the 2000 Nobel Prize in Physiology or Medicine for his research on the physiological basis of memory storage in neurons...

, the genus has been studied as a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...

 by neurobiologists, because its siphon-withdrawal response, as studied in Aplysia californica, is mediated by 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 allow several neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s to fire synchronously (Kandel et al., 2000). (See : Aplysia gill and siphon withdrawal reflex
Aplysia gill and siphon withdrawal reflex
The Aplysia gill and siphon withdrawal reflex is an involuntary, defensive reflex of the sea hare Aplysia californica, a large shell-less sea snail or sea slug...

) This quick neural response is necessary for a speedy reaction to danger by the animal. Aplysia has only about 20,000 neurons making it a favorite case to study for reductionist neuroscientists.


Species within the genus Aplysia are as follows.
This list follows the studies of Medina et al. who established a phylogenetic hypothesis for the genus Aplysia through study of the partial mitochondrial DNA (mtDNA) sequence data of ribosomal genes
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....

  • Aplysia brasiliana
    Aplysia brasiliana
    Aplysia brasiliana, common name the "mottled sea hare", or the "sooty sea hare", is a species of sea hare or sea slug, a marine opisthobranch gastropod mollusk in the family Aplysiidae....

    (Rang, 1828) Mottled sea hare, sooty sea hare (junior synonym of Aplysia fasciata; different geographical populations of the same species)
    • Distribution : West-Atlantic from New Jersey to Brazil, East-Atlantic around Ghana
    • Length : up to 27 cm
    • Color : variable

  • Aplysia californica (J.G. Cooper, 1863) California sea hare
    • Distribution : Northeast Pacific
  • Aplysia cedrocensis (Bartsch & Rehder, 1939)
    • Distribution : Northeast Pacific
  • Aplysia cervina (Dall & Simpson, 1901)
    • Distribution : West Atlantic
  • Aplysia cornigera Sowerby, 1869
    • Distributuion: Indian Ocean, West Pacific
  • Aplysia cronullae Eales, 1960
    • Distribution : Southwest Pacific
  • Aplysia dactylomela
    Aplysia dactylomela
    Aplysia dactylomela, common name the "spotted sea hare", is a species of large sea slug, a marine opisthobranch gastropod mollusc in the family Aplysiidae, the sea hares.-Distribution:...

    (Rang, 1828) Spotted sea hare
    • Distribution : 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...

      ; tropical and temperate seas.
    • Color : from pale gray to green to dark brown.
    • Description : large black rings on the mantle; good swimmer
  • Aplysia denisoni Smith, 1884
    • Distribution : Indian Ocean, West Pacific
  • Aplysia depilans (Gmelin
    Johann Friedrich Gmelin
    Johann Friedrich Gmelin was a German naturalist, botanist, entomologist, herpetologist and malacologist.- Education :Johann Friedrich Gmelin was born as the eldest son of Philipp Friedrich Gmelin in 1748 in Tübingen...

    , 1791)
    • Distribution : Northeast Atlantic, Mediterranean.
    • Description : thin, yellow inner shell
  • Aplysia donca (Ev. Marcus & Er. Marcus, 1960)
    • Distribution : North America, West-Atlantic
  • Aplysia dura Eales, 1960
    • Distribution : Southeast Atlantic, Southwest Pacific
  • Aplysia euchlora Adams in M.E.Gray, 1850
    • Distribution : Northwest Pacific
  • Aplysia extraordinaria
    Aplysia extraordinaria
    Aplysia extraordinaria, common name the "extraordinary sea hare", is a very large species of sea slug, more specifically a sea hare, a marine opisthobranch gastropod mollusk in the family Aplysiidae, the sea hares.- Further reading :...

    (Allan, 1932) (possibly = Aplysia gigantea)
    • Distribution : Western Australia, New Zealand.
    • Length : more than 40 cm
  • Aplysia fasciata (Poiret, 1798) ( Aplysia brasiliana Rang, 1828 is a junior synonym).
    • Distribution : East Atlantic, Mediterranean, West Africa, Red Sea
    • Length : 40 cm
    • Color : dark brown to black.
    • Description : sometimes has a red border to the parapodia and oral tentacles;
  • Aplysia geographica (Adams & Reeve, 1850) (?)
    • Distribution : Western Australia.
    • Length : 60 cm
    • Color : dark brown to black
    • Description : the skin secretions are very distasteful, washed-up specimens have been implicated in the deaths of dogs
  • Aplysia gigantea Sowerby, 1869
    • Distribution : Indian Ocean, West Pacific
  • Aplysia gracilis Eales, 1960
    • Distribution : Red Sea
  • Aplysia inca d'Orbigny, 1837
    • Distribution : Southeast Pacific
  • Aplysia juliana
    Aplysia juliana
    Aplysia juliana, common name the walking sea hare, is a species of sea slug, more specifically a sea hare, a marine gastropod mollusk in the family Aplysiidae, the sea hares.- Distribution:...

    Jean René Constant Quoy
    Jean René Constant Quoy was a French zoologist.Along with Joseph Paul Gaimard he served as naturalist aboard La Coquille under Louis Isidore Duperrey during its circumnavigation of the globe , and the Astrolabe under the command of Jules Dumont d'Urville...

     & Gaimard
    Joseph Paul Gaimard
    Joseph Paul Gaimard was a French naval surgeon and naturalist.Along with Jean René Constant Quoy he served as naturalist on the ships L'Uranie under Louis de Freycinet 1817-1820, and L'Astrolabe under Jules Dumont d'Urville 1826-1829...

    , 1832)
    Walking sea hare
    • Distribution: cosmopolitan, circumtropical in all warm seas
    • Color: various, from uniform to pale brown
    • Description: no purple gland, therefore no ink secretions; posterior end of the foot can act as a sucker
  • Aplysia keraudreni Rang, 1828
    • Distribution: South Pacific
    • Length: 25 cm
    • Color: dark brown
  • Aplysia kurodai (Baba, 1937)
    • Distribution: NW Pacific
    • Length: 30 cm
    • Color: dark brown to purplish black, dotted with white spots
  • Aplysia maculata Rang, 1828
    • Distribution : Western Indian Ocean
  • Aplysia morio (A. E. Verrill
    Addison Emery Verrill
    Addison Emery Verrill was an American zoologist. He was a student of Louis Agassiz at Harvard University and graduated in 1862...

    , 1901)
    Atlantic black sea hare, sooty sea hare
    • Distribution: Northwest Atlantic
    • Length: 40 cm
    • Color: black to deep brown; no spots
  • Aplysia nigra d'Orbigny, 1837
    • Distribution : Southwest Atlantic, South Pacific
  • Aplysia nigra brunnea Hutton, 1875
    • Distribution: New Zealand
      New Zealand
      New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

    • Length: 10 cm
    • Color: dark brown
  • Aplysia oculifera (Adams & Reeve, 1850) Spotted sea hare
    • Distribution: Indian Ocean; West Pacific; common along the north, east and south coast of South Africa
      South Africa
      The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

    • Length: 15 cm
    • Description: greenish brown, with small brown to black spots with white centres
    • Habitat: shallow bays and estuaries
    • Behaviour: hides by day; emerges at night to feed on seaweed
  • Aplysia parvula (Guilding in Moerch, 1863) Pygmy sea hare, Dwarf sea hare
    Dwarf sea hare
    The dwarf sea hare or pygmy sea hare, Aplysia parvula, is a species of sea slug, specifically a sea hare, a marine gastropod mollusc in the family Aplysiidae, the sea hares.-Distribution:This is a circumtropical sea hare...

    • Distribution : worldwide in warm to temperate seas
    • Length: 6 cm
    • Color: brown to green spots
  • Aplysia pulmonica Gould, 1852
    • Distribution : West Pacific
  • Aplysia punctata
    Aplysia punctata
    Aplysia punctata is a species of sea slug, a sea hare, a marine opisthobranch gastropod mollusk in the family Aplysiidae, the sea hares....

    Georges Cuvier
    Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...

    , 1803)
    • Distribution: NE Atlantic
    • Length: 20 cm
    • Color: very variable
  • Aplysia rehderi Eales, 1960
    • Distribution : Northeast Pacific
  • Aplysia reticulata Eales, 1960
    • Distribution : Southwest Pacific
  • Aplysia reticulopoda (Beeman, 1960) Net-foot sea hare
    • Distribution : Northeast Pacific
  • Aplysia robertsi Pilsbry, 1895
    • Distribution : Northeast Pacific
  • Aplysia rudmani Bebbington, 1974
    • Distribution : Indian Ocean
  • Aplysia sagamiana (Baba, 1949)
    • Distribution: East Australia, Japan; Northwest Pacific
  • Aplysia sibogae (Bergh, 1905) (?)(probably = Aplysia juliana)
  • Aplysia sowerbyi  Pilsbry, 1895
    • Distribution : Southwest Pacific
  • Aplysia sydneyensis (Sowerby, 1869)
    • Distribution: Australia
    • Length: 15 cm
    • Description: not clearly defined
  • Aplysia tanzanensis Bebbington, 1974
    • Distribution : Indian Ocean
  • 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. -...

    (Winkler, 1955) California black sea hare (possibly ?= Aplysia cedrocensis)
    • Distribution: Pacific Coast of California
    • Length: very big – up to 75 cm
    • Color: black
    • Description: no purple ink; huge internal shell
  • Aplysia willcoxi (Hellprin, 1886) (?)
  • Aplysia winneba Eales, 1957
    • Distribution : tropical East Atlantic

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