| Aplysiida | |
|---|---|
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| Aplysia californica, a typical sea hare displaying inking behavior | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Subclass: | Heterobranchia |
| Infraclass: | Euthyneura |
| Subterclass: | Tectipleura |
| Order: | Aplysiida P. Fischer, 1883 |
| Families | |
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| Synonyms | |
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TheorderAplysiida, commonly known assea hares (Aplysia species and related genera), are medium-sized to very largeopisthobranchgastropodmolluscs with a soft internal shell made of protein. These aremarinegastropodmolluscs in the superfamiliesAplysioidea andAkeroidea.
Thecommon name "sea hare" is adirect translation fromLatin:lepus marinus, as the animal's existence was known in Roman times. The name derives from their rounded shape and from the two longrhinophores that project upward from their heads and that somewhat resemble the ears of ahare.
Many older textbooks and websites refer to this suborder as "Aplysiida". The original authorPaul Henri Fischer described the taxon Aplysiida at unspecified rank above family.[1] In 1925Johannes Thiele established the taxon Aplysiida as a suborder.
Since the taxon Aplysiida was not based on an existing genus, this name is no longer available according to the rules of theICZN.[citation needed] Aplysiida has been replaced in the newTaxonomy of the Gastropoda (Bouchet & Rocroi, 2005) by theclade Aplysiomorpha.
The scientific name for the order in which they used to be classified, the Aplysiida, is derived from theGreek for "without a shield" and refers to the lack of the characteristic head shield found in the cephalaspidean opisthobranchs. Many Aplysiidans have only a thin, internal and much-reduced shell with a smallmantle cavity; some have no shell at all. All species have aradula and gizzard plates.
Jörger et al. (2010)[2] have moved this taxon (named as Aplysiida) to Euopisthobranchia.
The name "Aplysiomorpha" was preferred by Bouchet and Rocroi (2005) over "Aplysiida Fischer", 1883, but the authors now agree that there is a consistent usage for Aplysiida in the recent literature and that the older name must be preferred.[3]
Sea hares are mostly rather large, bulky creatures when adults. Juveniles are mainly unobserved on the shoreline. The biggest species,Aplysia vaccaria, can reach a length of 75 centimetres (30 in) and a weight of 14 kilograms (31 lb) and is arguably the largest gastropod species.[4]
Sea hares have soft bodies with an internal shell, and like all opisthobranch molluscs, they arehermaphroditic. Unlike many other gastropods, they are more or less bilaterally symmetrical in their external appearance. The foot has lateral projections, or "parapodia".[5]
Sea hares are herbivorous, and are typically found onseaweed in shallow water. Some young sea hares seemingly are capable of burrowing in soft sediment, leaving only their rhinophores and mantle opening showing. Sea hares have an extremely good sense of smell. They can follow even the faintest scent using theirrhinophores, which are extremelysensitive chemoreceptors.
Their color corresponds with the color of the seaweed they eat: red sea hares have been feeding on red seaweed. Thiscamouflages them from predators. When disturbed, a sea hare can release ink from its ink glands, providing a fluid, smoke-like toxic screen, adversely affecting its predators' olfactory senses while acting as a powerful deterrent. The toxic ink may be white, purple, or red, depending on the pigments in their seaweed food source and lightens in color as it spreads, diluted by seawater. Their skin contains a similar toxin that renders sea hares largely inedible to many predators.[citation needed] In addition to the colored ink, sea hares can secrete a clear slime akin to that released defensively byhagfish which physically plugs the olfactory receptors of predators like lobsters.[6][7]
Some sea hares can employjet propulsion as a locomotion and others move like stingrays but with greater fluttering fluidity in their jelly-like "wings". In the moving marine environment and without the sophisticated cognitive machinery of thecephalopods, their motion appears to be somewhat erratic, but they do reach their goals, such as the seabed, according to the wave-action, currents, or calmness of their area.[8][9]
Sea hares are consumed in several parts of the world. An example may be "酱爆海兔"[10] (jiàng bào hǎi tù), lit. "sauce-fried sea hare", aChinese dish featuring sea hare and occasionally squid quickly fried in a sauce.
InHawaii, sea hares, orkualakai, are typically cooked in animu wrapped inti leaves.[citation needed]
In coastal areas in theVisayas andMindanao islands in thePhilippines, long strands of eggs of the wedge sea hare (Dolabella auricularia, locally known asdonsol ordongsul in theVisayan languages) are traditionally eaten. The egg strands are known aslokot orlukot and are harvested from shallow rocks andseagrass meadows. They resemble twisted noodles (pancit) in appearance and texture, hence why they are also calledpansit-pansitan ("mock noodles") in some areas. They are usually green, but can be reddish to yellowish in color. They are often mistaken forseaweed and have a taste described as salty and sweet. They are usually eaten raw with vinegar and spices askinilaw, sauteed likepancit guisado, or added to soups like fishtinola.[11][12]
Egg masses of sea hares are also similarly eaten inSamoa,Kiribati, andFiji.[13]
Aplysia californica is a species of sea hare noteworthy for its use in studies of theneurobiology oflearning andmemory, due to its unusually largeaxons. It is especially associated with the work ofNobel LaureateEric Kandel.[14] Research surrounding theaplysia gill and siphon withdrawal reflex may be of particular interest with respect to this.[15]
