Dear Angel,
Thanks for your comments. I am glad we agree on most things. What I find most frustrating is how little anatomical information has actually been published. By information I mean diagrams and illustrations of actual dissections. Even Brunckhorst's extensive monograph (1993) has few anatomical diagrams and usually only the type species of each genus is described. This means that the only way to review such work is to do it again, which is just not practical. For example, there are a number of comparative tables in Brunckhorst which suggest that as well as the position of the anus, there are considerable anatomical differences in the foregut and reproductive systems of Phyllidia and Fryeria. I would like to be able to make my own judgement on that, but the published evidence is not there for me to do so. Similarly with species of Phyllidiopsis, it would be useful if sufficient evidence could be presented to the reader for them to make an 'armchair' judgement on the hypothesis being presented to them. I have searched the literature for some anatomical illustrations of different species which would allow me to get a feel for the similarities and differences but can't find them. One growing problem is that many authors are replacing illustrative information with data matrices and tables of character states. This makes it almost impossible for readers to make a judgement on the hypothesis being presented, unless they are willing to 'trust' the authors to have interpreted the anatomy correctly [NB: I don't include the well-illustrated Valdes & Gosliner, 1999 in this comment]. I realise that illustrations can be 'doctored' but at least if there are detailed illustrations available the reader can see what the author has in mind, and make a judgement on whether they agree with how the author has interpreted the anatomy. Without naming names, I once had a puzzling correspondence with a colleague over the anatomy of an animal. It only became clear when they sent me a diagram of the anatomy, that they had confused part of the reproductive system with the alimentary canal. Easy enough to do, but a fatal and untraceable error, if all a reader has to work on is a character matrix based on an anatomical error.

Sorry I am making this so long. Let's discuss you last point - the 'paraphyly' of Fryeria. I think its a bit early to say we understand the evolution of this group. In your cladistic analysis you only include one species of each genus and one branch of your cladogram ends up with an unresolved trichotomy consisting of Phyllidia varicosa, Fryeria marindica [in the middle] and Phyllidiella pustulosa. You may have later cladograms with more species analysed, but the one in your 1999 paper doesn't look as though the evidence for Fryeria nesting in the middle of a large Phyllidia clade is very strong. Have you published a later analysis with more species?
Best wishes,
Bill Rudman

Thanks Terry,
I think it would be wrong to give our readers the impression that all taxonomists are as polite and civilised as we are in our taxonomic debates. In fact, like all human endeavours, there are taxonomists who are outrageous, egotistical, self-opinionated, bigoted etc etc, and most of us have stories about colleagues and events which make humorous anecdotes in conference 'happy-hours'.

To return to our polite discussion. Basically I will be happy with any conclusion that is reached on the monophyly of the Porostomata, the position of Fryeria bayi and the relationship of Phyllidia and Fryeria. Interestingly, the concept of the Porostomata as a monophyletic group is more than 100 years old, but seemed to go out of fashion in the 1970s ironically because people were interested in evolutionary relationships and felt that the similar suctorial foregut in the Dendrodorids and Phyllidiids were just as likely to have evolved independently as to have had a common origin. It will certainly be interesting to see the publications on Gilianne's histological work and Angel's mitochondrial DNA.

My mention of the Atlantic species was really about the Phyllidiopsis - Fryeria bayi question. I have a philosophical difficulty with the same character apparently popping up independently a number of times in closely related groups. It seems quite logical to remove F. bayi from Fryeria but to place it in Phyllidiopsis and to merge Fryeria with Phyllidia means that we believe that there is some gene in the family which allows the anus to switch from dorsal to ventral, even within a single species. I think we should be asking geneticists whether this is a likely scenario.

I don't quite understand your point that removing the Fryeria clade from Phyllidia would render Phyllidia paraphyletic. This doesn't necessarily follow from your paper where you say "it is possible that members of the genus Phyllidia with a ventral anus could form a monophyletic subclade." Are you suggesting that perhaps we should consider Fryeria to be a subgenus of Phyllidia?
Best wishes,
Bill Rudman

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