(Alder & Hancock, 1851)
Little is known about this species. Thompson & Brown (1964) state that most UK records are from the Irish Sea, but the species was originally reported from Northumberland on the east coast. Records from outside the UK are problematic until identifications can be confirmed.
Scapa Flow, Orkney, intertidal, Scotland, U.K., North Atlantic, 29 March 1975, Sheltered rocky shore. Length: 6 mm and 10 mm. Photographer: Ian F. Smith.
In a separate message [#23075], Bernard Picton considers the animals photographed in Ian Smith's message #22871 are most probably Onchidoris inconspicua, a species which have never been previously photographed.
"I'm pretty certain that it is Onchidoris inconspicua. In the original description the pale yellow rhinophores, dull white gills and sprinkled brown spots are all mentioned. The illustration shows less spotting than in these individuals, but the nature of the spots is very similar, individually irregular in shape and distributed evenly but randomly. Some indication of spots on the tips of tubercles is apparent in the drawing. The underside is illustrated with a large dark patch of 'liver' and the description says "the liver appears in a large, broad patch of dark purple through the centre" exactly as shown in Ian's photograph of the underside. As far as I am aware this species has not been reliably reported since its original description except for a record by Chris Todd in his PhD study at Robin Hood's Bay, Yorkshire, North Sea. Thompson also gives records for the Irish Sea, Gullmarfjord and Arcachon, but as there are several very similar species it is difficult to be certain of these."
- Alder, J. and Hancock, A. 1845-1855, A monograph of the British nudibranchiate Mollusca parts 1-7, London, Ray Society
- Thompson, T.E. and Brown, G.H. (1976) British Opisthobranch Molluscs. Linnean Society of London / Academic Press
- Thompson, T.E. and Brown, G.H. (1984) Biology of Opisthobranch Molluscs Vol 2. Ray Society, London .
Rudman, W.B., 2010 (January 12) Onchidoris inconspicua (Alder & Hancock, 1851). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/onchinco
Re: Unknown Onchidoris from Scapa Flow, Scotland
From: Bernard Picton, January 12, 2010