Hypselodoris maridadilus from South Africa

Dear Valda,
In my opinion both these animals are Hypselodoris maridadilus which I described from Tanzania. The main external difference between it and the western Pacific species Hypselodoris whitei is that the gills and rhinophores are a uniform translucent orange or orange-red in H. maridadilus while in H. whitei they are both tipped with white. Yonow (1994) described a species from the Maldives, H. centunculus, which differs in having a whitish tip to the rhinophores but not the gills. Erwin Koehler's photo from the Maldives, which I have tentatively identified as H. maridadilus is identical in colour to the photo published by Yonow of H. centunculus.

At this stage I cannot say whether H. centunculus is a distinct species. If you look carefully at the rhinophores of H. maridadilus the tip sometimes apears to be very pale, obviously because the skin pigment is much more transparent when there is no layer of tissue behind it. What I can't tell from the photos of H. centunculus is whether the white tips of the rhinophores are caused by a white pigment or whether some trick of the light is making the translucent tips appear pigmented white.

•Yonow, N. (1994) Opisthobranchs from the Maldive Islands, including descriptions of seven new species (Mollusca: Gastropoda). Revue fr. Aquariol., 20(4): 97-130.

Best wishes,
Bill Rudman.