Dear Dishant,

Your animal is almost identical in colour to Brian Mayes photo from Oman [message #19677] which I identified as Hypselodoris carnea.

Yours has fewer white lines than the Oman animal but that is a link to the multi-lined animals from South Africa. Another similarity are the dark translucent brown patches with black spots  along each side of the mantle which are present in all specimens. The main difference is the colour of the mantle edge. The yellow is absent in southern animals and the blue has changed to a deep purplish plum colour. But Colin Ogden [message #21508] has shown is colour variants from South Africa which have a submarginal band of yellow which could be the ornage of the yellow spots in your animal. Chromodoris aureopurpurea shows a similar shift in yellow.

I could turn out to be quite wrong but we still have a lot to learn about variation in both these white-lined chromodorids and in the blue and yellow spotted Hypselodoris infucata group of species.. 

Best wishes,
Bill Rudman

Dear Colin,

I'm afraid I can't contribute much at this stage. The yellow seems to be a thin layer,  but I am not sure if the 'sand-grainy' material beneath is part of the colony or not. Some of these non-spicuate sponges incoporate sand grains into their skeleton. I will of course discuss it with my sponge expert, Dr Pat Bergquist, but even if we can't make a positive identification, it will certainly be a useful bit of information if we find it on a bright yellow sponge in future. Perhaps next time its stucture will make it a little more identifiable.

Best wishes,
Bill Rudman

Dear Colin,

It certainly looks as though the brown background colour in your upper photos is from the internal digestive gland and the yellowish band around the mantle edge could possibly be the result of mantle gland contents.

Concerning the yellow sponge which your animal looks to be feeding on. I am afraid I can't see any structural details which I can use. Amost all species of Hypselodoris feed on species of Dysidea, or related genera, and like the sponge in the lower photo the colony has cone-like shapes all over and a radiating pattern and network of structural fibres which are usually quite obvious. Although at times the colonies can be reasonably large and thick, often they consist of a very thin layer over the substrate, or over another sponge colony. It's possible in this case that the sponge the slug is eating is a fine layer over the yellow sponge which we can't really see, but I really can't say. It would be interesting to see what the sponge cover looked like just above the slug? If you have a photo showing just a bit more above the slug it might be useful. As to learning more about sponges, I'm afraid there is not an easily available general book, and no easy way for amateurs - or non-sponge specialists - to identify most sponges. This is for a host of reasons, not the least being that there is still a lot of research needed to sort out sponge taxonomy. Another big problem is that sponge colonies are often very variable in shape and even colour and so species can often only be identified by cutting sections through the tissue for microscopic examination. In sponges with skeletal spicules, we need to examine not only the shape of the spicules, but how they are arranged in the sponge colony. Most sponges eaten by chromodorids present even greater problems because they lack spicules, so we are left with examining the arrangement of the fibrous network to determine species and families. My advice is to try and become familiar with your local sponge fauna even if you can't actually name species. If you find slugs taking a particular interest in particular sponges, keep taking photos of both the sponge and the slug. It is proving an invaluable help.

Thanks very much,
Bill Rudman

Dear Colin,
It's a good photo at 6 mm in situ. My guess is that this is a juvenile of either Hypselodoris carnea or H. capensis. In colour it looks more like H. capensis, but since that species seems to be restricted to the temperate Cape region, my guess is that your animal is a very juvenile H. carnea.

Best wishes,
Bill Rudman

Dear Brian,
As you will see from the various discussions in messages concerning these two species, you are not the only one who has difficulties in distinguishing them externally. I guess the simplest difference is that H. capensis is a cool temperate species and H. carnea has a tropical distribution, at least in the Indian Ocean. On those grounds your animal is H. carnea.

Best wishes,
Bill Rudman

Dear Colin,
My first thought was that you had Hypselodoris carnea and the very similar looking H. capensis, but the locality would seem to preclude that. The bright patch seems to be something to do with the colour of the mantle glands, which in Hypselodoris are often much larger behind the gills. What you didn't mention is that the second specimen is nestled into a colony of a sponge (Family Dysideidae) which is almost certainly its food sponge. I am pretty sure, in this case, that the white mass at the front of the body is its everted buccal bulb. A nice new feeding record!
Best wishes,
Bill Rudman

Dear Colin,
I am pretty sure this is Hypselosoris carnea. Terry Gosliner says, that the very similalr looking H. capensis doesn't extend up the Natal coast. Concerning the gills conracting. This is entirely normal for one major group of the dorids, which has a chamber into which the gill circlet is able to retract. The higher classification of the dorids is under quite extensive research at the moment but in the past the dorids have been divided in to two superfamilies called the Cryptobranchia [= Eudoridoidea] and the Phanerobranchia [=Anadoridiodea]. - Crypto = hidden, Phanero = naked, branchia = gills. As the name suggests the other major group of dorids, the Phanerobranchia have gills that can contract, but don't have a pocket to retreat into.
Best wishes,
Bill Rudman

Dear Valda,
I am pretty sure this is a species of Hypselodoris and my first guess would be that it is a juvenile of one of the terrible twins, Hypselodoris carnea and H. capensis. The orange band on the rhinophores and the orange-edged gills fit that species and the pair of white lines on the mantle could easily be the beginnings of the multiple white lines which typify both species.

Then again it could be something else.
Best wishes,
Bill Rudman

Dear Gordon,
At first glance I thought of Thorunna daniellae but apart from other considerations, I think there are clear signs of longitudinal opaque white lines on the mantle which would suggest a pale form of Hypselodoris carnea.

I would welcome anyone else's ideas
Best wishes,
Bill Rudman.

Thanks Terry,
It would be intersting to know whether they feed on different sponges, or whether their egg ribbons differ. Not that that would help identify them from photos. I'll place them all under H. carnea. If you have a chance, a photo of H. capensis would be a nice comparison to add to the Forum for those without access to your book.
Bill Rudman.

Dear Valda,
Looking at both Terry's book and the recent Hypselodoris paper I must agree that there seem to be no good colour distinctions.

I also looked at presence and absence of spots on the foot. In Terry's book H. carnea has spots on the foot and H. capensis doesn't. However my guess would be that your 45 & 47 are both H. carnea and one has foot spots and the other doesn't. I don't know if spots on the mantle behind the gills is important but your 45, 47 and Terry's H. carnea have mantle spots behind the gills and his H.capensis and your 46 do not.

Gosliner & Johnson (1999) identify the photos of H. carnea (p.235) and H. capensis (p.234) in Debelius, 1996 as H. carnea.

Hopefully Terry will take pity on us and let us know what he thinks.

Cheers,
Bill Rudman.

Reference: Gosliner, T.M. & Johnson, R.F. (1999) Phylogeny of Hypselodoris (Nudibranchia: Chromodorididae) with a review of the monophyletic clade of Indo-Pacific species, including descriptions of twelve new species. Zoological Journal of the Linnean Society, 125: 1-114.