Elysia tomentosa
Jensen, 1997

Order: SACOGLOSSA
Superfamily: ELYSIOIDEA
Family: Elysiidae

DISTRIBUTION

Probably Indo-West Pacific.

PHOTO

Koumac Beach (=Baie de Ouanap), near Koumac, New Caledonia, 20°34'S, 164°16'E, Mixed soft and hard substrate, grassbeds, algae, 23 October 1993,
Upper Photo: 2 animals, 14, 20mm long alive, AM C200589. Lower Photo: 50mm long alive, on Caulerpa taxifolia. This specimen shows the elongate renal ridge behind the pericardium. AM C200588. Photos: Bill Rudman

This species was described from the Abrolhos Ids in northwestern Australia. In colour it was described as olive green, 'more or less covered in tiny white dots which may form larger white dots especially on the head and the distal part of the inner parapodial surface.' The edge of the parapodia were described as having an orange or light red margin and the rhinophores were either olive green or reddish brown. Orange brown dots are scattered dorsally as are small black spots many of which are ocellate. The papillae are white or transparent if along the parapodial margin. The body is extremely papillose and many of the papillae, especially on the parapodial margins, are branched. There is a long renal ridge extending a considerable distance behind the pericardium, and there is an anterior transverse groove across the foot. Grows up to 50mm long alive.

Jensen compares E. tomentosa with E. expansa (O'Donoghue, 1924), which was also described from the Abrolhos Islands, but in that species there are fewer papillae, they are never branched, and there is a black line at the parapodial edge [see Jensen 1993]. It is possible that E. pilosa Risbecia 1927, from New Caledonia, is the same species, but Risbec's description of the external features of his species are not clear enough to make an adequate comparison.

Specimens illustrated here fit Jensen's description well but they usually differ in having a black line on the inside and outside of the parapodia, along the inside edge of the pink parapodial margin. The presence and absence of this line seems to be variable in this species. Jensen does not mention its food, but records from New Caledonia and Sydney suggest it feeds on Caulerpa taxifolia.

See close-up photos of papillae and colour pattern. See also Elysia cf. tomentosa Page. The animals on that page may be this species, but appear much more papillate than illustrated by Jensen (1997) [see message from Kathe Jensen with photo of type material].

References:
• Jensen, K.R. (1993) Sacoglossa (Mollusca, Opisthobranchia) from Rottnest Island and central Western Australia. [In]: Proceedings of the 5th International marine Biological Workshop: The marine Flora and Fauna of Rottnest Island, Western Australia. (Eds: Wells, F.E.; Walker, D.I.; Kirkman, H., Lethbridge, R.) Western Australian Museum, Perth, 207-253.
• Jensen, K.R. (1997) Sacoglossa (Mollusca,Opisthobranchia) from the Houtman Abrolhos Islands and central Western Australia. [In:] The Marine Flora and Fauna of the Houtman Abrolhos Islands, Western Australia. (Ed: Wells, F.E.) Western Australian Museum, Perth, 307-333.
• O'Donoghue, C. H. (1924) Report on Opisthobranchiata from the Abrolhos Islands, Western Australia, with description of a new
parasitic copepod. Journal of the Linnean Society of London, 35: 521-579, pls. 27-30.
• Risbec, J. (1928). Contribution à l'étude des nudibranches Néo-Calédoniens. Faune des Colonies Françaises, 2: 1-328.
• Risbec, J. (1953) Mollusques nudibranches de la Nouvelle-Caledonie. Faune de l'Union Francaise, Paris: Libraire Larouse, 15: 1-189.

Authorship details
Rudman, W.B., 2003 (July 23) Elysia tomentosa Jensen, 1997. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/elystome

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