Ortea in Ortea, Valdés & García-Gómez, 1996
Cap d'Antibes, 20 m, Antibes, France, Mediterranean sea, 05 June 2006, vertical rock. Length: 15 mm. Photographer: Dominique Horst.
Another interesting 'blue chromodorid' from the Mediterranean which is very similar in colour to some forms of H. villafranca and juvenile H. orsinii. The background colour of the mantle and the body is dark blue. The mantle has a median white line running from between the rhinophores back to the gills where it forms a ring around the edge of the gill pocket. There can be a thin irregular white line on each side half way between the midline and the mantle edge. The mantle edge has a deep orange border which can change to white around the anterior and posterior ends. The blue rhinophores have a white line up the posterior midline, and the blue gills have a white line along the edge of the rachis. There is a white line along each side of the body and these join posteriorly to form a single mediodorsal line on the posterior tip of the foot.
Ortea et al, (1996) say that H. gasconi can be differentiated from H. villafranca because the mantle border in H. gasconi is a 'strong' orange. There seem to be few anatomical differences between the two species.
Ortea, J., Valdes, A. & Garcia-Gomez, J.C. (1996) Review of the atlantic species of the Family Chromodorididae (Mollusca: Nudibranchia) of the blue chromatic group. Avicennia (Suppl. 1): 1-160
Rudman, W.B., 2006 (June 6) Hypselodoris gasconi Ortea in Ortea, Valdés & García-Gómez, 1996. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/hypsgasc
June 8, 2006
From: Dominique Horst
Again, I have a doubt about the following dorid. I initially thought it was Hypselodoris tricolor, but I noticed that the yellow line bordering the mantle is turning to white at the front and the back. I know (now) that color is not a feature determining a species, but having a look all around on the net, I've found pictures identified as Hypselodoris gasconi ... which fits pretty well.
I realized also that there is a recent message ot the Forum [#16566] which you replied to already. So it seems that this animal is traveling from Adriatic to the Mediterranean sea thisweek...
Locality: Cap d'Antibes, 20m, Antibes, France, Mediterranean sea, 05 June 2006, vertical rock. Length: 15mm. Photographer: Dominique Horst.
firstname.lastname@example.orgHorst, D., 2006 (Jun 8) Hypselodoris gasconi from Antibes ?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16807
Thanks for these photos. The 'blue chromodorids' have been puzzling experts for 150 years. In the recent message you mention I express some doubts about how to distinguish H. gasconi from some of the colour forms of H. villafranca. Hopefully a local expert can help us. Both species are compared in the most recent revision of these animals but there seem to be few anatomical or colour differences between them.
All I can say is that your animals don't have a second white line near the mantle border, and so fit photographs of H. gasconi in the original description [Ortea et al, 1996: Fig 12A]. On that basis alone I have identified your animals as H. gasconi but I would appreciate some comments from local experts on how to distinguish the two species.
Concerning your comment that you now know 'that color is not a feature determining a species'. I hope I didn't mislead you in my earlier remarks. Colour is a good character in identification, but we need to know from other characters (such as anatomy) just what parts of the colour pattern are unique to a particular species. If we can do that, then the animal's colour pattern, or at least parts of it, become a valuable tool in accurate identification.
- Ortea, J., Valdes, A. & Garcia-Gomez, J.C. (1996) Review of the atlantic species of the Family Chromodorididae (Mollusca: Nudibranchia) of the blue chromatic group. Avicennia (Suppl. 1): 1-160