Cuthona genovae, a new species for the Forum

Dear Miquel,

Thanks for this interesting additon to the Forum. Concerning your two questions.

Food: Unfortunately the literature has many food records which are unsubstantiated. When someone records a species of nudibranch they usually include a description of its shape or colour and hopefully a drawing or photo. Unfortunately when they record a food item, they don't think it is just as necessary to describe the food or include a photo or drawing or deposit a sample in a museum collection. In the case of hydroids, it may be easier in Europe, but in less studied parts of the world, getting hydroids identified is quite difficult - there are few experts and they want to get on with their research rather than act solely as identification services. I can't say in this case, but often hydroids in the past have been incorrectly identified - and probably still are. One other problem is that hydroids often settle and grow in mixed colonies, the stalks and 'root' systems of several species being intertwined. It is quite possible to misidentify the actual hydroid an aeolid is interested in in such a situation. Another complication is that Cuthona genovae has long been confused with Cuthona foliata, which is very similar in external features (Bouchet, 1976). Greg Brown (1980) and Michael Miller (1961) report C. foliata feeding on a variety of hydroids. Picton & Morrow (1994) confirms that C. foliata feeds on various hydroids but has only found C. genovae feeding on Tubularia so it is possible that food records for C. foliata have been unintentionally added to those for C. genovae. I haven't checked for recent records and research, but since C. genovae is fairly common in the Mediterranean it could be an interesting little project for someone.

Concerning Trinchesia or Cuthona. I haven't much more to add to my earlier message [#21285].  When I wrote that, I had not seen Debelius & Kuiter but predicted that they would not give reasons or references to why they had decided to use Trinchesia. I have now seen the book and can  find no references to any information in the book. In his foreward, Helmut Debelius says his books present 'scientifically proven information'  but in my understanding of science, books that don't acknowledge the work of others or refer to the source of their information aren't doing their job. So I can only presume that they base their usage on Michael Miller's paper (2004). All I can repeat is that I feel there is little point in us changing present usage from Cuthona to Trinchesia until a full review of the family is undertaken and a more robust hypothesis of the phylogeny of the family developed.

• Bouchet, P. (1976) Trinchesia genovae (O'Donoghue, 1926) éolidien méconnu du littoral Méditerranéen. Beaufortia, Zoological Museum Univ. Amsterdam 26: 235-242 .
• Brown, G.H. (1980) The British species of the aeolidiacean family Tergipedidae (Gastropoda: Opisthobranchia) with a discussion of the genera. Zoological Journal of the Linnean Society 69: 225-255
• Miller, M. C. (1961) Distribution and food of the nudibranchiate Mollusca of the south of the Isle of Man. Journal of Animal Ecology, 30: 95-116.
• Miller, M. C. (2004) An appraisal of the identity of the New Zealand species of the aeolid family Tergipedidae (Gastropoda: Opisthobranchia). Journal of Natural History 38: 1183-1192.
• Picton, B. E. and Morrow, C. C. (1994) A Field Guide to the Nudibranchs of the British Isles. London, Immel Publishing Ltd.  143pp.

Best wishes,
Bill Rudman