Elysiella pusilla
'cylindrical form'
Order: SACOGLOSSA
Superfamily: ELYSIOIDEA
Family: Elysiidae
PHOTO
Koumac Beach (=Baie de Ouanap), near Koumac, New Caledonia, mixed grassbeds, algae, on Halimeda October 1993, 3 specimens, (all 17mm long alive). Upper photo showing 2 colour forms and more Elysia-like 'posture' of animals on Halimeda with cylindrical segments. In lower photo note the normal cryptic resting pose of the mottled animal on a terminal segment. Note also on the left of the photo how a lighter coloured subterminal segment, and its two terminal segments, have a remarkable resemblance to a resting elysiid. PHOTOS: Bill Rudman.
In all reports of Elysiella pusilla the point that is noted is its flattened cryptic appearance. This is true of specimens on plants with large flattened segments as I have illustrated on a separate page, but if you remove animals into a dish they become much more Elysia-like in shape when they begin crawling. I have seen no previous reports of individuals from species, or forms, of Halimeda with cylindrical segments. From my observations in New Caledonia their parapodia are held more erect and the whole body is held upright. However, when similar sized animals from both plant forms are put together in a dish it is impossible to separate them in colour or shape.
See Page 1 where 'typical' flattened form of Elysiella pusilla is illustrated.
Reference:
• Bergh, L.S.R. (1872). Malacologische Untersuchungen. In: C.G. Semper, Reisen im Archipel der Philippinen, Wissenschaftliche Resultate. Band 2, Heft 3: 137-176, Pls. 17-20.
Rudman, W.B., 1999 (July 24) Elysiella pusilla 'cylindrical form'. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/elyspus2
