|Aplysia californica, a typical sea hare, shown here releasing a cloud of purple pigment, probably as a reaction to being disturbed.|
Members of the Aplysiidae have an atrophied inner shell (in contrast with the nudibranchs, 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 can reach up to 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.
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.
Sea hares are hermaphrodites, 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.
- 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 in 1809. Rafinesque introduced the new name Laplysinia in 1815. In 2001 Bouchet & Rocroi advocated the attribution of the name Aplysiidae to Lamarck.
Classification after N. B. Eales (1984):
- 海鹿亞科 Aplysiinae Lamarck, 1809
- 黃花瓣螺亞科 Dolabellinae Pilsbry, 1895
- Dolabriferinae Pilsbry, 1895
- Notarchinae Mazzarelli, 1893
- 海兔属 Aplysia Linnaeus, 1767：模式屬
- Barnardaclesia Eales & Engel, 1935
- Bursatella Blainville, 1817 - the only one species: Bursatella leachii Blainville, 1817
- 黃花瓣螺屬 Dolabella Lamarck, 1801
- Dolabrifera Gray, 1847
- † Floribella Woodring, 1970
- Notarchus Cuvier, 1817
- Paraplysia Pilsbry, 1895
- Petalifera Gray, 1847
- Phyllaplysia Fischer, 1872
- Stylocheilus Gould, 1852
- Syphonota H. Adams & A. Adams, 1854 - the only one species: Syphonota geographica (A. Adams & Reeve, 1850)
- Genera brought into synonymy
- Aclesia Rang, 1828: synonym of Bursatella Blainville, 1817
- Aplysiella P. Fischer, 1872: synonym of Petalifera Gray, 1847
- Busiris Risso, 1826: synonym of Notarchus Cuvier, 1816
- Laplysia Linnaeus, 1767: synonym of Aplysia Linnaeus, 1767
- Neaplysia J. G. Cooper, 1863: synonym of Aplysia (Neaplysia) J. G. Cooper, 1863 represented as Aplysia Linnaeus, 1767
- Phycophila A. Adams, 1861: synonym of Aplysia (Phycophila) A. Adams, 1861 represented as Aplysia Linnaeus, 1767
- Pruvotaplysia Engel, 1936: synonym of Aplysia (Pruvotaplysia) Engel, 1936 represented as Aplysia Linnaeus, 1767
- Ramosaclesia Iredale, 1929: synonym of Bursatella Blainville, 1817
- Siphonotus A. Adams & Reeve, 1850: synonym of Syphonota H. Adams & A. Adams, 1854
- Tullia Pruvot-Fol, 1933: synonym of Aplysia (Tullia) Pruvot-Fol, 1933 represented as Aplysia Linnaeus, 1767
- Varria Eales, 1960: synonym of Aplysia (Varria) Eales, 1960 represented as Aplysia Linnaeus, 1767
- 貝科基本解說：台灣Aplysiidae 海鹿科貝類共 8 種. 臺灣貝類資料庫 （中文（繁體））.
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- Vue Z., Kamel B. S., Capo T. R., Bardales A. T. & Medina M. (2014). "Comparative analysis of early ontogeny in Bursatella leachii and Aplysia californica". PeerJ 2: e700 doi:10.7717/peerj.700