August 3, 2005
From: Jussi Evertsen
Hi Bill, and Kaare.
Concerning message #14460: The reason I used Eubranchus vittatus and not Eubranchus cingulatus, is that the descriptions given by Alder & Hancock in their monograph (both are described and illustrated in there), best fits E. vittatus. The rarity of a species is not nescessarily true, that we time and time again see here in Norwegian waters where divers just recently have started looking for nudibranchs. In Brown (1980) they are kept as separate species, but characters do overlap. Alder & Hancock separate the species on the shape of the cerata (they are clavate in E. vittatus and ovate in E. cingulatus, and that E. vittatus has wrinkled rhinophores, whilst E. cingulatus is supposed to have smooth ones). I was fortunate enough to get 7 specimens from Kaare, from 5 to 20 mm in length. They had a translucent body with superficial light and dark brown pigmentation on the dorsal side in a patchy manner all the way down to the tail (the smallest specimens being the lightest in colour). White minute dots formed lines and blotches on the body. The cerata were club shaped (as clavate in Alder & Hancock), meaning they were more or less sylindrical in shape, but expanding towards the apex. They were set in 8-10 rows, with max 8 cerata counted in the foremost row. The cerata had white caped tips with a tinge of gold, and three distinct brown bands. The rhinophores had white pigmentation from the tip and maybe 1/4 down, had a brown band, and where wrinkled from the basis half way up, the wrinkling being more distinct in the bigger specimens. The oral tentacles were shorter than the rhinophores and smooth, with white tips and a brown band.
From the literature, Edmunds & Kress (1969) and Thompson & Brown (1984) all keep them as separate species, and as long as there has not been done a thorough investigation, we are but to consider all species available. These specimens happens to fit Alder & Hancock's (1852) description.
email@example.comEvertsen, J., 2005 (Aug 3) Re: First record of Eubranchus vittatus in Norway. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/14464
This species is one of the probems which still arise from early descriptions based in very few animals. We can concentrate on the particular features of a single specimen or try an envisage how the description of a sinmgle specimen relates to variation within a population. Thompson & Brown (1984) consider there are problems with earlier identifications of what they call E. cingulatus, noting that Schmekel & Portmann's (1982) account referred to E. doriae, and so possibly did Edmunds & Kress's (1969). They also note that they had earlier done the same (Thompson & Brown, 1976: Fig 89). Why I mentioned rarity is that Thompson & Brown's (1984) description of E. vittatus was based on a single specimen, so they had no opportunity to compare living populations of the two nominal species and see just how much variability occurred.
Hopefully Bernard Picton will have a moment to comment on this