{{Short description|Order of gastropods}} {{Redirect|Sea hare|the fairy tale|The Sea-Hare}} {{Redirect|Sea bag|the type of luggage|Duffel bag}} {{About|the clade of gastropod molluscs|the similarly named clade of extinct jawless fishes|Anaspida|the informal group of reptiles|Anapsida|the freshwater crustacean family|Anaspididae}} {{Automatic taxobox |image=Aplysiida (10.3897-zse.95.33707) Figure 2.jpg |image_caption= Aplysiida type specimens | image2 = Aplysia_californica.jpg | image2_caption = ''Aplysia californica'', a typical sea hare displaying inking behavior | taxon = Aplysiida | authority = P. Fischer, 1883 | subdivision_ranks = Families | subdivision = *Superfamily Akeroidea **Akeridae *Superfamily Aplysioidea **Aplysiidae | synonyms_ref= | synonyms = * Anaspidea * Aplysiomorpha |display_parents= 5 }}
The order '''Aplysiida''', commonly known as '''sea hares''' (''Aplysia'' species and related genera), are medium-sized to very large opisthobranch gastropod molluscs with a soft internal shell made of protein. These are marine gastropod molluscs in the superfamilies Aplysioidea and Akeroidea.
The common name "sea hare" is a direct translation from {{langx|la|lepus marinus}}, as the animal's existence was known in Roman times. The name derives from their rounded shape and from the two long rhinophores that project upward from their heads and that somewhat resemble the ears of a hare.
== Taxonomy == Many older textbooks and websites refer to this suborder as "Aplysiida". The original author Paul Henri Fischer described the taxon Aplysiida at unspecified rank above family.<ref>{{cite book | title=Manuel de conchyliologie et de paléontologie conchyliologique fasc. 6| last=Fischer| first=P.| year=1883| pages=513–608| publisher=Savy | location=Paris}}</ref> In 1925 Johannes Thiele established the taxon Aplysiida as a suborder.
=== 2005 taxonomy === Since the taxon Aplysiida was not based on an existing genus, this name is no longer available according to the rules of the ICZN.{{Citation needed|date=July 2014}} Aplysiida has been replaced in the new Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005) by the clade Aplysiomorpha.
The scientific name for the order in which they used to be classified, the Aplysiida, is derived from the Greek 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 small mantle cavity; some have no shell at all. All species have a radula and gizzard plates.
=== 2010 taxonomy === Jörger et al. (2010)<ref name="Jörger 2010">{{cite journal | last1 = Jörger | first1 = K. M. | last2 = Stöger | first2 = I. | last3 = Kano | first3 = Y. | last4 = Fukuda | first4 = H. | last5 = Knebelsberger | first5 = T. | last6 = Schrödl | first6 = M. | year = 2010 | title = On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia | journal = BMC Evolutionary Biology | volume = 10 | issue = 1| page = 323 | doi = 10.1186/1471-2148-10-323 | pmc = 3087543 | pmid=20973994 | doi-access = free }}</ref> have moved this taxon (named as Aplysiida) to Euopisthobranchia.
===2017 taxonomy=== 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.<ref>Gofas, S. (2010). [http://www.marinespecies.org/aphia.php?p=taxdetails&id=1752 Aplysiomorpha. In: MolluscaBase] (2017). Accessed through: World Register of Marine Species at marinespecies.org on 2017-03-30</ref>
==Description== 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 {{convert|99|cm|in}} and a weight of {{convert|14|kg|lb}} and is arguably the largest gastropod species.<ref>{{cite web |editor1=Rudman, W.B. |editor2=Firminger, P.I. |date=15 July 2010 |title=''Aplysia vaccaria'' |website=The Sea Slug Forum (seaslugforum.net) |place=New South Wales, AU |publisher=Australian Museum |url=http://www.seaslugforum.net/find/aplyvacc}}</ref>
Sea hares have soft bodies with an internal shell, and like all opisthobranch molluscs, they are hermaphroditic. Unlike many other gastropods, they are more or less bilaterally symmetrical in their external appearance. The foot has lateral projections, or "parapodia".<ref name=IZ>{{cite book |author=Barnes, Robert D. |year=1982 |title=Invertebrate Zoology |place=Philadelphia, PA |publisher=Holt-Saunders International |isbn=0-03-056747-5 |page=376}}</ref>
==Life habits== [[File:Sea hare DSC01663.jpg|thumb|left|Sea hare ''Dolabella auricularia'' at Big Island of Hawaii]] Sea hares are herbivorous, and are typically found on seaweed 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 their rhinophores, which are extremely sensitive chemoreceptors.
Their color corresponds with the color of the seaweed they eat: red sea hares have been feeding on red seaweed. This camouflages 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|date=August 2009}} In addition to the colored ink, sea hares can secrete a clear slime akin to that released defensively by hagfish which physically plugs the olfactory receptors of predators like lobsters.<ref>{{cite web |last1=Ceurstemont |first1=Sandrine |title=New Scientist TV: Sea hares use sticky weapon to cripple predators |url=https://www.newscientist.com/blogs/nstv/2013/03/sea-hare-sticky-goo.html |date=2013-03-28 |access-date=2016-09-30}}</ref><ref>{{cite web |last1=Peterson |first1=Coyote |title=Inked by a Giant Slug! - YouTube |website=YouTube |url=https://www.youtube.com/watch?v=3CGhng_VviU |date=2016-09-30 |access-date=2016-09-30}}</ref>
Some sea hares can employ turbo jet 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 the cephalopods, 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.<ref name='Packard1972'>{{Cite journal| first1 = A.| title = Cephalopods and Fish: the Limits of Convergence| journal = Biological Reviews| volume = 47| issue = 2| last1 = Packard| pages = 241–307| year = 1972| doi = 10.1111/j.1469-185X.1972.tb00975.x| s2cid = 85088231}}</ref><ref>For details of locomotion in the Aplysiomorpha, see {{cite journal |author1=Bebbington |author2=Hughes |title=Locomotion in ''Aplysia'' (Gastropoda, Opisthobranchia) |journal=Journal of Molluscan Studies |year=1973 |volume=40 |issue=5 |pages=399–405|doi=10.1093/oxfordjournals.mollus.a065237}}</ref>
==Human use== Sea hares are consumed in several parts of the world.
In Hawaii, sea hares, or ''kualakai'', are typically cooked in an imu wrapped in ti leaves.{{citation needed|date=January 2015}}
In coastal areas in the Visayas and Mindanao islands in the Philippines, long strands of eggs of the wedge sea hare (''Dolabella auricularia'', locally known as ''donsol'' or ''dongsul'' in the Visayan languages) are traditionally eaten. The egg strands are known as ''lokot'' or ''lukot'' and are harvested from shallow rocks and seagrass meadows. They resemble twisted noodles (''pancit'') in appearance and texture, hence why they are also called ''pansit-pansitan'' ("mock noodles") in some areas. They are usually green, but can be reddish to yellowish in color. They are often mistaken for seaweed and have a taste described as salty and sweet. They are usually eaten raw with vinegar and spices as ''kinilaw'', sauteed like ''pancit guisado'', or added to soups like fish ''tinola''.<ref name="Pepito">{{cite journal |last1=Pepito |first1=Ador R. |last2=Delan |first2=Gloria G. |last3=Asakawa |first3=Manabu |last4=Ami |first4=Letecia J. |last5=Yap |first5=Emelia Encarnacion S. |last6=Olympia |first6=Minerva SD. |last7=Yasui |first7=Kaori |last8=Maningo |first8=Aurelia G. |last9=Rica |first9=Rachel Luz V. |last10=Lamayo |first10=Ma. Helian A. |title=Nutritional Quality of the Egg Mass Locally Known as “Lukot’ of the Wedge Seahare Dolabella auricularia (Lightfoot, 1786) |journal=Tropical Technology Journal |date=October 2015 |volume=19 |issue=1 |doi=10.7603/s40934-015-0007-z|doi-access=free }}</ref><ref>{{cite news |last1=Santos |first1=Jamil |title='Lokot' na tila pansit, alamin kung anong uri ng lamang-dagat na malinamnam |url=https://www.gmanetwork.com/news/balitambayan/talakayan/939863/lokot-na-tila-pansit-alamin-kung-anong-uri-ng-lamang-dagat-na-malinamnam/story/ |access-date=20 March 2025 |work=Balitambayan |agency=GMA News |date=19 March 2025}}</ref>
Egg masses of sea hares are also similarly eaten in Samoa, Kiribati, and Fiji.<ref>{{cite journal |last1=Liguez |first1=Chency Grace O. |last2=Tabugo |first2=Sharon Rose |title=Antibacterial activity of sea hare (''Dolabella auricularia'') egg string extracts against potentially pathogenic bacteria |journal=Biodiversitas |date=December 2023 |volume=24 |issue=12 |pages=6675-6683 |doi=10.13057/biodiv/d241229|doi-access=free }}</ref>
''Aplysia californica'' is a species of sea hare noteworthy for its use in studies of the neurobiology of learning and memory, due to its unusually large axons. It is especially associated with the work of Nobel Laureate Eric Kandel.<ref>{{Cite web|author=Edythe McNamee and Jacque Wilson|title=A Nobel Prize with help from sea slugs|url=https://www.cnn.com/2013/05/14/health/lifeswork-eric-kandel-memory/index.html|access-date=2020-10-31|website=CNN|date=14 May 2013 }}</ref> Research surrounding the aplysia gill and siphon withdrawal reflex may be of particular interest with respect to this.<ref>{{Cite journal|last1=Agranoff|first1=Bernard W.|last2=Cotman|first2=Carl W.|last3=Uhler|first3=Michael D.|date=1999|title=Invertebrate Learning and Memory|url=https://www.ncbi.nlm.nih.gov/books/NBK28212/|journal=Basic Neurochemistry: Molecular, Cellular and Medical Aspects. 6th Edition|language=en}}</ref>
==Gallery== <gallery> File:Sea hare, Aplysia dactylomela, 12 04 2009 2-00pm.jpg| Sea hare ''Aplysia dactylomela'' File:Sea hare, Aplysia dactylomela, 12 04 2009 2-02pm.jpg| ''Aplysia dactylomela'' showing mouth </gallery>
== References == {{reflist|22em}}
== External links == {{Commons category|Aplysiomorpha}} {{Wikispecies|Aplysiida}} * [http://www.cabrillomarineaquarium.org/exhibits/socal-species-details.asp?id=3 California Brown Sea Hare] — Cabrillo Marine Aquarium * [http://seaslugsofhawaii.com/general/aplysiidae.html Aplysiidae (sea slugs) of Hawaii]
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Category:Euopisthobranchia Category:Taxa named by Paul Henri Fischer Category:Taxa described in 1883