Dear Brian,

Your animal certainly fits the description of H. rudmani, but I don't claim to be an expert on identifying it. It certainly looks very similar to Colin Ogden's photos [message #17554] but as I say in a later message [#19989], H. rudmani has similarities to H. sagamiensis. One feature which is very clear in your photos is the row of inverted triangles along each side of the mantle which are slightly darker than the background colour of the rest of the mantle. One character I used to think was unique to H. infucata was similar triangles which appeared darker than the background colour because they were translucent rather than pigmented. If this is H. rudmani then that species is a very good mimic of H. infucata, or it is in fact a very white pigmented colour form of H. infucata. Clearly I would prefer it to be a good species, but I still think we have some sorting out to do in this colour group of species.

For example in an earlier message from Teresa Zuberbühler [#21614] she has a photo showing a group of animals feeding on a sponge. I identified them as H. infucata but was puzzled by the spots on the gills of the largest specimen which are characteristic of H. kanga. On relooking at that photo I can see that the animal with spotted gills does not have the characteristic inverted triangles while all the others do. On reflection it looks like Zubi's photo shows both H. infucata and H. kanga feeding together. Another puzzle is Binaymin Koretz's photo [message #15795] of a strange colour form of H. infucata from the Red Sea. Perhaps this is H. rudmani?

As you can see, I am not a confident identifier of H. rudmani at present. No doubt as we learn more about these species it will become clearer, but at present I am somewhat cautious.

Best wishes,
Bill Rudman

Dear Colin,

I'm glad you are beginning to have heretical thoughts. I have been having similar thoughts myself which leads me to the conclusion that Hypselodoris sagamiensis and Hypselodoris rudmani might just be the geographical extremes of one species. In the original description of H. rudmani there is no mention of a yellow submarginal band down each side of the mantle and I can see none in the accompanying photo which looks very similar to Valda Fraser's photo [#1630]. However your animal [#17554] definitely has a row of submarginal yellow spots which links it to the western Pacific H. sagamiensis.

I can't say I really want to suggest H. rudmani may be just a junior synonym of H. sagamiensis but its a good example of the value of accumulating more records of all these species. I guess we are going to have to rely on you and any of your colleagues in South Africa to find and photograph some more specimens so we can see just what its colour range is in the southwestern Indian Ocean. It would also be interesting to get a photo of its egg ribbon. Nishina Masayoshi has given us an excellent photo [#7720] of the egg ribbon of H. sagamiensis and the relatively large eggs and wavy edge to the egg ribbon are quite unusual. If your South African animal has a similar egg ribbon I would be pretty convinced the two are but one species.

Best wishes,
Bill Rudman

Dear Colin,
Often after new species are described there is what could be called a 'settling in' period when we begin to look more closely at similarly coloured animals and try and work out just how much colour variation there is in the new species. Often we have no information on the juveniles, which sometimes may just have some parts of the adult pattern. I guess this specimen and some of the others I have tentatively called H. rudmani fit into that scenario. I suspect this may be a juvenile H. rudmani but there is always the possibility that there are a group of similarly coloured species in southern Africa which we still have to sort out.

Best wishes,
Bill Rudman

Dear Colin,
I am pleased to say these are Hypelodoris rudmani. I must say we haven't had much luck at finding animals which fit this species well, but I am pretty confident that these are it
Best wishes,
Bill Rudman

Dear Colin,
I am glad you sent two photos. The upper one certainly seems to be Hypselodoris rudmani, but the lower one is an unnamed animal I am calling Hypselodoris cf. maculosa. I have discussed this in a bit more detail in a separate message [#14850].
Best wishes,
Bill Rudman

Dear Lindsay,
If this photo had been sent to me from the east coast of South Africa I would have had no hesitation in identifying it as Hypselodoris rudmani. It is almost identical to photo 130 in Gosliner, 1987, except that the blue spots in your photo are larger and quite diffuse around the edges. However at 8mm I suspect your animal was a juvenile. If you look at my photos of the similarly coloured Hypselodoris infucata you will see that in juveniles the blue and yellow spots are proportionally very large, becoming much smaller in adults.

My feeling is that it is Hypselodoris rudmani. If so, your find increases its known distribution from one side of the Indian Ocean to the other.

An interesting find,
Bill Rudman.

Dear Valda,

This is also Hypselodoris rudmani. Hypselodoris sp.2 and Hypselodoris sp. 3 in Terry Gosliner's 1987 South African book are both colour forms of H. rudmani. Your earlier photo is of the form with quite opaque white patches and reticulations.
Best wishes,
Bill Rudman.

Dear Valda,

I can't throw this one away! Terry Gosliner and Rebecca Johnson have just kindly named it Hypselodoris rudmani.

Best wishes,
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.