Glossodoris rubroannulata - natural history [1]

Dear David,
I sometimes think I sound like a squeaky wheel always asking for photos of these animals 'doing things' but your message perfectly illustrates the value of learning more about their biology and natural history. Althought it is vital to know their anatomical details, and I have spent my career looking at anatomical details, sometimes there just don't seem to be sufficient differences to be sure just what is going on. So looking at things like egg ribbons and feeding behaviour can give us another suite of characters to consider.

As Nerida Wilson has shown [#8611], chromodorids which lay a flat egg ribbon are almost certainly a separate phylogenetic group to other species of Chromodoris that don't. And my recent feeding review [#20272] shows that these flat-egg producing chromodorids also feed on different sponges as well. 

Which brings me to your animals. Glossodoris is another genus with some puzzling anatomical subgroups, and G. rubroannulata belongs to one subgroup with similarities to 'Chromodoris'. Your discovery of this egg ribbon with extra-capsular yolk is interesting, because up until now species of Chromodoris, but not species of Glossodoris, have been reported to have this type of egg ribbon [see Fact Sheet]. The other interesting thing is the sponge your animal is eating. Species of Glossodoris seem to feed exclusively on thorectid sponges, and this is not a thorectid. I am pretty sure I know what it is but I am sending it off to Pat Bergquist for a definitive identification. It seems from your observations that we will need to seriously consider whether G. rubroannulata is indded a Glossodoris.

Thanks again for these interesting finds

Best wishes,
Bill Rudman