Dendrodoris senegalensis

July 6, 2003
From: Bill Rudman

I have identified the Dendrodoris from Senegal in Marina Poddubetskaia's recent messages [juveniles, subadults, adults] as Dendrodoris senegalensis, which as its name implies was originally described from Senegal (Bouchet, 1975).

I have translated Bouchet's description of the external colour to read:
The nine individuals observed alive measured from 7 to 60 mm fully extended. Juveniles from [approx 7 to 20 mm long] are translucent reddish, as are the rhinophores and gills, which have whitish tips. In the older individuals, the mantle is translucent, ranging from pinkish red to brownish yellow, with brown and red marblings. The edge of the mantle is undulating and carries pink radiating lines. The underside of the mantle, and the foot, are a plain translucent greyish colour. Some individuals have more red pigment, which masks the underlying red and brown mottling.

More recently Valdes et al (1996) have reviewed the dendrodorids of the Atlantic and proposed some new species, including two from the West African coast, D. angolensis and D. guineana which both have similarities to Marina Poddubetskaia's animals. In particular, their photo of D. angolensis is almost identical to Marina's photos of adults from Senegal. The only difference is that in D. angolensis the tips of the rhinophores are described as red, while in D. senegalensis they are white, and 'usually' there is a thin red line at the mantle edge. D. guineana does not appear to have any red pigmentation, and the adult mottled colour pattern is described as grey rather than brown.

In their description of D. senegalensis from Cape Verde Island they describe the external morphology as:
"The background colour of the body is very variable, it can be white, yellow, orange, brown, grey or black. Most of the specimens studied have dark grey or black spots on the dorsum. No relationship between size and pigmentation has been observed in adult specimens. The rhinophores and the gills are similar in colour to the body, with the apex (in the rhinophores) and the exterior border (in the gills) white. Juvenile specimens are uniformly red. No spicules were observed. The mantle margin is wide and strongly striated. It is about as wide as ½ the foot"

Absent from this description is any mention of the red patches described by Bouchet and clearly visible in Marina's photos. These three species, especially D. senegalensis and D. angolensis show many external similarities. Some differences between the three species, in the shape and width of ducts in the reproductive system and in the detail of the penial spines are noted. It would be interesting if someone were to examine the anatomy of many more specimens of each of these species to see just how consistent the anatomical differences are. If these three very similar looking species, all living in close geographic proximity, are confirmed to be good species, it would suggest we should look very closely at the 'variable' species we have accepted in the Indo-West Pacific. Perhaps they are clusters of different species. Unfortunately no one has yet shown that the the few anatomical characters we have at our disposal - penial spine morphology, relative lengths and widths of reproductive ducts - are valuable in distinguishing species. We need to know that they are consistently different between species, and do not vary during growth.

• Bouchet, P. (1975) Nudibranches nouveaux des cotes du Senegal. Vie et Milieu, 25(1): 119-132
• Valdes, A., Ortea, J., Avila, C. & Ballesteros, M. (1996) Review of the genus Dendrodoris Ehrenberg, 1831 (Gastropoda: Nudibranchia) in the Atlantic Ocean. Journal of Molluscan Studies, 62: 1-31.

Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Jul 6) Dendrodoris senegalensis. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10394

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