Stiliger bellulus an egg-eating sacoglossan

March 16, 1999
From: Bernard Picton

Note added 26 March 2009: I have reverted to the name Calliopaea bellula for this species. See Fact Sheet.

Hi Bill,

Following on from Philine aperta I enclose 3 scans of Stiliger bellulus. One shows a mass of individuals feeding on the eggs of Philine aperta (quality is poor as they were taken with a Nikonos close-up kit in poor visibility). Another photo taken at the same time shows a single animal on a Philine - hitching a ride? These were taken in Carlingford Lough during our Northern Ireland Survey in 1984 by Christine Howson and Dave Connor. The larger image is of an animal collected intertidally in NW Spain in 1978. Our database has records from several sheltered sites in SW Ireland where Philine was usually also present.

As a sacoglossan Stiliger bellulus might be expected to feed on algae, but these observations suggest that it feeds on Philine eggs (and possibly other
Opisthobranch eggs). In 1974 Lemche described a new species Calliopoea oophaga (named from its habit of eating Philine eggs) but this description is likely to be based on juvenile Stiliger bellulus (see Thompson & Brown, Biology of Opisthobranch Molluscs, p.167 for discussion). Thompson also mentions that the Mediterranean species Stiliger vesiculosus is oophagous.

Bernard

bernard.picton.um@nics.gov.uk

Picton, B., 1999 (Mar 16) Stiliger bellulus an egg-eating sacoglossan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/680

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