Re: Food & colour in Tritonia hombergi

May 3, 2001
From: Bernard Picton

Hi Bill,
Regarding small juvenile Tritonia hombergi, I have seen these on Alcyonium digitatum and as Jane says, they are well-camouflaged by their matching colour. However they must suffer high predation as juveniles can be very numerous but result in very few full-grown individuals at the same site. I wonder if in fact there is a balanced polymorphism with high fish predation controlling the colour of surviving individuals in shallow water - Alcyonium is usually in strong tidal streams or wave action and can also be in deep turbid water where fish would not see the Tritonia well. Tritonia hombergi adults seem to be more common in dredge hauls from deeper water and seem to be partly nocturnal or in crevices by daytime in shallow water. I suspect that we are not seeing the main breeding populations by diving.

Oddly Alcyonium on the west coast of Ireland is nearly all orange/yellow in colour whilst in SW England it is almost all white. In Scotland both colours occur.

Bernard Picton

bernard.picton.um@nics.gov.uk

Picton, B., 2001 (May 3) Re: Food & colour in Tritonia hombergi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4272

Thanks Bernard,
Bill Rudman

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Tritonia hombergii

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