Phyllidiopsis bayi or Fryeria bayi

Dear Alma,
Thanks for mentioning the Valdés & Gosliner (1999) paper. I have read it two or three times wondering how I should respond on the Forum. Traditionally in taxonomy, when major changes, or major ideas are proposed, it takes some years before a consensus has emerged on the 'rightness' or 'wrongness' of the proposal. With so few workers in the field it takes time before others are in the position to re-examine the evidence, do their own research and publish their thoughts. With the world wide web, and rapid ways to publish our thoughts, like the Forum, a new way of dealing with new ideas will have to emerge. If we act immediately, every time a new taxonomic decision is published, then I suspect we will descend into chaos very quickly. My feeling on this paper was to wait and see what others thought of the paper.

But since you have raised the topic we might as well open it up for discussion. it is after all the Sea Slug Forum. I have a few problems with it. Firstly I think that before we can clarify the relationship between the dendrodorids and the phyllidiids we need to have a clearer understanding of the homologies between the various parts of the foregut. Perhaps further histological studies will help or perhaps it may be possible to undertake embryological studies. However at the moment it seems to me we don't know. The most sophisticated cladistic analysis is only as good as the data that is put into it.

The main concern of the paper is to consider the phylogenetic relationships of all the 'radula-less' dorids. There is little discussion or much evidence presented concerning the inter-relationships of the phyllidiids. In the paper the authors decide that the genus Fryeria is superfluous and of the two species of Fryeria they deal with, they place one, F. marindica in the genus Phyllidia, and the other, F. bayi in Phyllidiopsis. They assert that the only character separating species of Fryeria from other phyllidiids is the position of the anus - opening ventrally in Fryeria and dorsally in all other genera. They may be right, but I think they raise many questions which I think deserve a much fuller study.

It is no surprise that the position of the anus has been used as a key character but Brunckhorst (1993) considers there are other characters in the foregut, and reproductive system that do differentiate the genera. Now again, he may be wrong, but I would like to see a publication that presents the evidence in more detail. I think we need to know about more than just the type species of these genera and we need to know just how much intraspecific variability there is in some of these characters.

To my knowledge, one specimen of one species, Phyllidiopis blanca, has shown variability in the position of the anus. It was described from the Pacific coast of central America (Gosliner & Behrens (1988) and one specimen was discovered to have a ventral anus. This one specimen seems to be the reason the authors consider the ventral anus to be a feeble character.

To the position of the Mediterranean Fryeria bayi. To my knowledge very few specimens have been examined. Valdes & Gosliner (1999) on the basis of the elongate buccal bulb and fused oral tentacles, consider that it should be considered a species of Phyllidiopsis despite its ventral anus. They might be right. However so few specimens of this species seem to have been examined that perhaps the reported ventral anus is an unusual occurrence in the species. Perhaps both the Atlantic species are better placed in Phyllidopsis. It does not necessarily follow that all Indo-West species of Fryeria should be placed in Phyllidia.

It seems a bit premature, on the basis of the peculiarites with these two Atlantic species, which may not be congeneric with the Indo-West Pacific species of Fryeria, to assert that they present sufficient evidence to show that Fryeria and Phyllidia are synonymous. Ventral gills do occur at times as an anomaly, after all Chromodoridella mirabilis Eliot 1905 was based on an aberrant animal of Hypselodoris infucata and Scott Johnson's photo shows a specimen of Chromodoris geometrica with the same feature. But the point is that these are unusual developmental faults. We wouldn't think of using them to suggest a phylogenetic relationship, so perhaps we shouldn't give the peculiarities of the two Atlantic phyllidiids much phylogenetic weight until we know more about their occurrence.

In summary, I think Valdes & Gosliner's paper presents some interesting ideas but I think we need more information. I also think that sorting out the validity of Fryeria is a separate question from the monophyly of the 'Porostomata'.

I'm sorry for such a long answer to your very short suggestion. At present I don't feel able to agree or disagree with the Valdes-Gosliner proposal that the radula-less dorids are a monophyletic group. I think in the long run it will depend on a fuller understanding of the homology of the foregut organs. When such a preponderance of characters are related to the alimentary canal, it does not matter whether you use your brain and a pen, or a sophisticated cladistics program, or both, the evidence must have a tendency to veer towards a close relationship.

Any thoughts very welcome
Best wishes,
Bill Rudman