Dear Terence,

Thanks for your rapid response. I have included two photos above, which are from the last of your sequence of photos and show the nudibranch alongside the sponge siphon. I first thought it looked as though the Hypselodoris was aiming for this sponge siphon but then I noticed that in the first photo in your sequence, when the slug is furthest from the siphon, it is moving past another small colony of the same sponge [see rings in lower photo].

In your close-up, the fibrous skeleton doesn't seem right for the most likely families this animal would eat, so I think it is all just a coincidence.

Your effort is certainly not a waste of time, for these animals don't always do what they are supposed to do. If we start to get more records of it associated with this sponge we may need to change our mind.

Best wishes,
Bill Rudman

Dear Terence,

If you look at the messages attached to the Hypselodoris bayeri Fact Sheet you will see that I suspect this to be a colour form of H. bayeri rather than of H. acriba [see message #22632 for example]. Unfortunately the original descriptions of these two species were not that clear, and both seem to be variable in colour, but I think my interpretation fits the descriptions better. Unfortunately a lot more fieldwork is needed before some of the identification problems with Caribbean species can be sorted out.

Whatever its name, I am interested in what sponges these nudibranchs feed on. I first thought the pink colour in your photos was a thin layer of coralline algae over the underlying rock but I noticed a sponge siphon [see top of lower left close-up] so I suspect the whole of the substrate is covered with a thin sponge layer. If by chance you have other photos taken at the same time, perhaps you could have a look and see if you have any that show the sponge in more detail?

Best wishes,
Bill Rudman

Dear Wayne,

More photos of these puzzling caribbean chromodorids are always welcome. Although photos alone will not resolve the puzzles, I have found them extremely valuable in the past when you are trying to formulate the question to ask. For example can the animals I am calling H. acriba and H. bayeri on the Forum be just colour forms of one species. And is the animal in Lureen Ferretti's recent message [#22617] also a colour form? One problem is that some of the existing species were not well described, and another problem is that species of Hypselodoris and Chromodoris are well-known mimics, with groups of similarly coloured species evolving in the same geographic region. As I mentioned earlier, [message #7999], Eveline Marcus considered your animal to be a colour form of  H. bayeri, while in Carribean Sea Slugs it is considered a possible form of H. acriba.

Your animal could well be associated with the bright blue sponge in  your photos - which I suspect is a species of Dysidea. Interestingly this is the same sponge which is illustrated in Carribean Sea Slugs as the food of Hypselodoris sp. 3 - which I suspect is part of the H. bayeri complex. However most species of Hypselodoris feed on dysideid sponges so we can't make too much of them feeding on the same sponge.

Sorting out problems like this can't be done in an a chair 1000s of km away. I suspect what is needed is a local research worker who is able to study populations over a number of years, and record colour variability, study anatomy and biology and has the help of dedicated amateurs who can make extra collections and observations. Visiting researchers, no matter how skilled, can only collect small samples in place and time, and as we can see from the present situation, this can lead to confusion rather than clarification.

• Valdes, A., Hamann, J., Behrens, D.W. & DuPont, A. 2006. Caribbean Sea Slugs. Sea Challengers.

 Best wishes,
Bill Rudman

Dear Lureen,

This is an interesting find. From the sponge it is feeding on - a species of Dysidea - and its general shape, I'm pretty sure it is a species of Hypselodoris, and it certainly doesn't appear to fit any named species. On looking through Caribbean Sea Slugs it would appear to be a colour form of the species they call Hypselodoris sp. 3 [pp 164-5]. However, as I discuss in response to Linda's interesting finds in the Chromodoris binza- C. neona group [message #22560], we still have a lot to learn about the Caribbean fauna, and I don't think it helps at this stage to consider or name every new colour pattern as a new species.

Your animal seems to be the same as Ellen Muller's animals from Bonaire [message #21716] which I am calling Hypselodoris bayeri, and Phillip Gillette's photos [message #13022 ] give a good example showing the blue & yellow lines breaking up into spots in different animals. I note that in Caribbean Sea Slugs, H. bayeri is used for the lined animals and H. marci for the spotted forms.

Ones thing they all have in common is that half way down each side of the mantle there is a darker patch and often a darker orange line at the mantle edge. In this way they all have similarities to H. ruthae. The one difference with H. ruthae, is that in that species only the inner edge of the gills is lined with purple. In your animal there is a purple line only at the tip of each gill, but I can't see if it is on the outer edge, inner edge or both. In Ellen Muller's animals both the inner and outer edge of the upper half of the gills is lined purple while in Philip Gillette's both edges of the whole gill are lined. In Caribbean Sea Slugs a distinction is made between purple lines on the rhinophores and purple rhinophores but it seems that in some animals the lines diffuse to cover much of the rhinophore, so this dustinction may not be valid. I can't really say how many species there are at present in this yellow/orange-lined group. What makes it more difficult is that we know that this family is well known for having species mimicking each other in colour pattern.

Ellen Muller has a good photo of the egg ribbon of her colour 'form' and it seems to be the same as that in Caribbean Sea Slugs for their Hypselodoris sp. 3. It would be nice to get photos of egg ribbons from some of the other colour 'forms'. If they are markedly different we would at least know there is more than one species involved.

In short, I don't know if yours is an unnamed species, but whatever it is, it is one more piece of the jig saw puzzle.

• Valdes, A., Hamann, J., Behrens, D.W. & DuPont, A. 2006. Caribbean Sea Slugs. Sea Challengers. 

Best wishes,
Bill Rudman

Dear Pam,

That was a nice find - as I have discussed before, I am pretty sure this is a colour form of Hypselodoris bayeri, but more work needs to be done on the Caribbean species before we really understand what is going on.

Best wishes,
Bill Rudman

Dear Ellen,

Thanks for this valuable observation. This animal belongs to a somewhat confusing group of species which are still not sorted out. I think the most likely situation is that some of these 'species' were described from single specimens, which in fact represented colour variations of just one species with a very variable colour pattern. The most obvious difference is that in some animals there are yellow-brown and blue longitudinal lines while in others the blue can be reduced to a scattering of spots and the rest of the background becomes yellow-brown. Phillip Gillette's photos [message #13022 ] give a good example showing the blue lines breaking up into spots.

I may be quite wrong, as another feature of chromodorids is that species sometimes mimic other species in appearance, so it is possible we are looking at a case of mimicry. If they are different species, then hopefully some of these colour differences can be linked to anatomical differences, but sometimes anatomical differences are too subtle to be useful. Your inclusion of an egg ribbon however is very valuable, because often egg masses can give us a clue.  Hopefully, in time, other egg ribbons, which can be identified to particular colour forms will be found. I also note in Caribbean Sea Slugs that this colour form is reported to feed on a blue sponge of the genus Dysidea. If you have any photos showing the sponge you found these animals on, it could be an interesting addition. Species of Dysidea are the usual food of species of Hypselodoris but there is always a possibility that one of the 'colour forms' of this blue-lined/blue-spotted group eats a different type of sponge.

Best wishes,
Bill Rudman

Dear Per,

This species is on the Forum from Bonaire as Hypselodoris sp 5 [#9824] but it is also identified as H. bayeri. I am afraid it is one of a group of Caribbean species which were not well defined when they were first named. As we know very little about their colour variability it is still almost impossible to decide how many species there are. Other possible names are H. marci and perhaps H. acriba.

Best wishes,
Bill Rudman

Dear Florent,
Thanks for these photos. Although they look a bit like Hypselodoris sp. 5, this is one of the colour forms of Hypselodoris bayeri  On fact your animals looks very similar to the photo accompanying Marcus & Marcus's original description of the species. It suggests that the rhinophores can vary in colour from uniform purple all over, the animals like this where the purple is mainly concentrated near the tip. Looking at your photos, I suspect that animals in earlier messages from St Kitts [#12949] and Honduras [#15451] which I tentatively considered Hypselodoris sp. 5. are almost certainly H. bayeri.

One of the reasons I welcome more photos of species already present on the Forum is that every variation gives us further insight into understanding the full picture
Best wishes,
Bill Rudman

Dear Valda,
Your animal exactly matches a photo Eveline Marcus sent me [message #7999] which she identified as H. bayeri. It was also from the Virgin Islands. As I mention in the earlier message the main difference between this colour form and the one described by Marcus & Marcus (1967), when they named this species, is that it had a pattern of dark blue spots around the mantle edge rather than the radiating lines of your animal. However in a photo from Florida [#13022] we can see an animal with a spotted margin, but also with some small radiating lines suggesting this is a variable feature, as did Eveline Marcus.

Since we know so little about these species, your photo is a valuable contribution to our knowledge. It will be interesting to whether similar links been H. bayeri and H. acriba turn up, as there are many similarities between these two species.

Best wishes,
Bill Rudman

Note added 26 June 2006: This is almost certainly a colour form of H. bayeri. See message #16979]

Thanks Les,
Yes this is what I am calling Hypselodoris sp. 5. Interestingly your animals show differences in the colour of the mantle border - small spots in one, large blotches in the other, and possibly differences in the rhinophore colours. I wouldn't be surprised if Hypselodoris sp. 5 and H. bayeri, and perhaps H. marci, turn out to be forms of one species, but unfortunately the two named species were not well described, so its difficult to know what they are. Combine that with the fact that we don't know whether we are dealing with one variable species of a number of similarly coloured species, and you get an idea of the problem. This problem is not going to be solved by someone giving names to a few apparently distinct colour forms. What we need is someone to study populations of these animals throughout the Caribbean, I am sure if there are really different species it will show up in different egg ribbons, development types, or even food choice.
Best wishes,
Bill Rudman

Note added 26 June 2006: This is almost certainly a colour form of H. bayeri. See message #16979]

Dear Kelly,
Thanks for these photos. We have had a few good photos of Caribbean chromodorids in the last couple of days. I am afraid there are no easy answers at the moment. I wonder whether your animal is an an extreme colour form of  Hypselodoris bayeri as illustrated in Phillip Gillette's recent message [#13022] ?  I am not sure if Hypselodoris sp. 5 is a good species. Perhaps there are two? I agree the white rhinophores with purple tips that some specimens have seems distinctive but there are others with pale purple rhinophores with deeper purple tips. Clearly we need more information on these animals, so photos such as yours are very useful.
Best wishes,
Bill Rudman

Dear Phillip,
Thanks for these photos. As you will have noted from the correspondence on the Forum I have had my doubts about many of the animals identified as H. bayeri in the literature. None of them have fitted the original description very well. These photos of yours do indeed fit Marcus' description almost exactly. The colour obviously varies from animals with a number of thin yellow longitudinal lines down the mantle, each outlined in black as in Marcus's description (and your uppermost photo), to animals in which the yellow lines are less clear and the blue spots more dominant, as in your photo alongside.
Best wishes,
Bill Rudman

Thanks Ron,
We still have a lot more to learn about this group. Almost every photo I get seems a bit different. I decided to treat the light purple rhinophore with a dark purple tip in Brian's photo to be a 'dark form' of those with a white rhinophore with a purple tip - but I could be wrong. We have two problems. Firstly we can't be sure of the colour pattern of the type specimens Marcus' species. Secondly we have no idea how many species we are dealing with and just how variable they are in colour. I'm afraid I put any data I get with photos so I'm afraid at thois stage we can't say whether colour variation is size related.
best wishes,
Bill Rudman

Dear Néstor,
It's good to get some more information on this group of species. I don't think the confusion surrounding this group of species can be blamed on Thompson's misidentification, which is on the Forum as Hypselodoris sp 5. The confusion is caused by the original description being based on two specimens, which in a species with a variable colour pattern is an inadequate sample. Clearly the Caribbean region has a group of similarly coloured species which are still not adequately understood.

Looking at your photos, I am now beginning to wonder whether the two animals that Marcus & Marcus had available to them when they described H. bayeri are in fact the same species. Your animal looks like Marcus & Marcus's colour plate Pl 1, fig 2, while the line drawing, Fig 76 [which was based on a colour slide of a second specimen], has a more reticulate pattern of yellow like the animal in Dave Behrens' message.

One thing that makes me wonder if there are two species is that in some photos the gills seem simple with a black or dark blue line up the outer edge, while in other photos, such as yours, the gills are really triangular in outline with the outer face being pale purple or blue and the edges bright yellow. This is not always easy to determine from slides, so I am not sure which gill type Marcus & Marcus were describing. We also don't know which of their two specimens they based their colour description on. The only way this can be sorted out is for a lot more Caribbean animals to be studied in detail.

I wouldn't be at all surprised if your animal turned out to be the one I am calling Hypselodoris sp. 4, although in most photos it seems to have a series of pale spots down the outer face of each gill. Another animal with a close similarity to your animal - including the yellow edging to the gills - is illustrated in Humann, 1999 [p. 233] as Hypselodoris acriba.

Thanks for these interesting photos. I have kept your latero-ventral photo at a larger size because it shows the arrangement of the mantle glands very well. Thanks also for the radula photos in your other message.
Best wishes,
Bill Rudman

Dear Néstor,
Thanks for these photos. They look very like the teeth illustrated by Marcus & Marcus in their original description. However they described an aberrant first lateral tooth as a central tooth and used this character to erect a new genus Felimare.
best wishes,
Bill Rudman

Thanks Dave,
The black spots around the edge of the mantle in Jeff Hamann's photo are certainly more as described by the Marcus's than in the photo I posted, and the rhinophores in Jeff's photo show only a hint of the spectacular blue of the other photo. I hesitated about posting the Marcus' photos, as I didn't know who the photographers were, and there was little accompanying data, so I am glad you have found them useful.
Cheers,
Bill Rudman