Aplysia gigantea
Sowerby, 1869

Order: ANASPIDEA
Superfamily: APLYSIOIDEA
Family: Aplysiidae

DISTRIBUTION

Common in southwestern corner of Western Australia [Duke of Orleans Bay, east of Esperance to Bluff Point, north of Geraldton].

PHOTO

Upper: animal washed up at Geraldton, Western Australia. See Peter Taylor's message. Photo: Peter Taylor.
Lower: Bicton Baths, Swan River, Western Australia, 20cm long, 30 December 2002, Photo: Masoud Abadi.

This giant Sea Hare can grow to 60cm in length, and are uniformly dark brown or black in colour. They can swim for short periods by flapping their large parapodia. It is considered that this species is restricted in range to the southwestern corner of Western Australia, but it is possible that it is identical to the large swimming Aplysia extraordinaria from eastern Australia. Wells (1986) redescribed A. gigantea but unfortunately did not compare it with A. extraordinaria.

Wells (1986) notes that A. gigantea is found spawning in shallow water during summer and early autumn, and is found most commonly from January to March. During summer, beach strandings of hundreds of animals can be found [see Mass Mortality Page]. He also describes a mating aggregation at Canal Rocks at 21m, March 1985:
" Mating groups of 2,3,5,8 and 17 animals were found, with each animal climbing up the back of the one in front and acting as a male for it. Spawn are typically aplysiid and orange in colour." [See Sea Hare mating Page]. See numerous messages below describing Sea Hares washing up on beaches and poisoning dogs who lick or eat them.

There is some problem with the identity of this species because it was first described from the shell alone, the locality accompanying the shells - "Swan River", being equivalent to "Western Australia" at the time. The size of this species differentiates it from all other species known from Wstern Australia. Unfortunately the original description and illustration (Sowerby in Reeve, 1869) gives no indications of size (other than 'large') and their is no scale on the accompanying plates. Presumably the aplysiid shells in Reeve are drawn to the same scale which would make the shells of A. gigantea at least 3 times the size of most other species of Aplysia illustrated. Surprisingly neither Wells (1986) nor Eales (1960) illustrate or describe the type specimen shells which are held at the British Museum.

References:
• Eales, N.B. (1960) Revision of the world species of Aplysia (Gastropoda, Opisthobranchia). Bulletin of the British Museum (Natural History). Zoology, 5(10): 1-404.
• Sowerby, G.B. (1869) Monograph of the Genus Aplysia Plates 1-10. [IN] Reeve, L.A., (1869) Conchologia Iconica Vol, 17. Reeve: London.
• Wells, F. E. (1986) A redescription of the sea hare Aplysia gigantea Sowerby, 1869. Journal of the malacological Society of Australia, 7(3-4): 173-180.

Authorship details
Rudman, W.B., 2002 (March 5) Aplysia gigantea Sowerby, 1869. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/aplygiga

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