Re: Glossodoris sedna from Utila, Honduras

Dear Ray,
Certainly we sometimes can't be sure with species which are found in two or more disjunct geographic areas. You will see I have often discussed how difficult it is to know where some well-known hitchhikers, such as Thecacera pennigera originated. Of course others such as the lessepsian migrants are usually obvious because we know the fauna of the Mediterranean quite well.

You are of course right when you say there are species which occur naturally on both sides of the Panama Isthmus, but this does mean that all species found on both sides are naturally occurring. I guess G. sedna is considered 'native' to the east Pacific because it was first found there and has quite a wide distribution there. While G. sedna had just a limited distribution in the Florida - Bahamas region it was reasonable to assume it was an import, but the Honduras record suggests it is either spreading or perhaps may have a much wider Caribbean distribution, which could either be natural or from human intervention.

There is at least one Glossodoris in the Atlantic, G. ghanensis, but it hasn't to my knowledge reached the west Atlantic. Concerning Glossodoris moerchi. Web-based databases can be a trap as they are usually not well edited or updated. That species was originally described as Goniodoris picturata by Moerch - a preoccupied name which was later changed to Chromodoris moerchi by Bergh. The generic names in the chromodorids became terribly confused for about a hundred years and at one stage almost everything was placed in Glossodoris. Whatever its correct genus placing, the original description is not good enough to be sure what Moerch was talking about.

So to wrap up, I guess it pays to keep an open mind on some of these distributions. With our present state of knowledge it seems logical to consider G. sedna to be native to the East Pacific only, but we just don't know how good our knowledge is.
Best wishes,
Bill Rudman