Dear David,

Thanks for these excellent photos. As I commented in Gary's message [#22089], your photos of this species and G. rubroannulata [message #20602] are of great value.

Best wishes,
Bill Rudman

Dear Gary,

Thanks for this excellent find. With Dave Mullins' photos [message #22094] which I am also posting today, I should be able to get this sponge identified. Interestingly it looks very similar to the sponge in Dave's earlier message showing G. rubroannulata feeding [message #20602]. I have almost got enough new sponge records now to arrange a session with Prof Bergquist to check their identities. From the available information, species of Glossodoris feed exclusively on thorectid sponges, but as we all know, these slugs don't seem to keep up with the scientific literature. To my untutored eye these sponges look more like dysideids, but I need expert advice. Interestingly both G. rubroannulata and G. vespa belong to a group of species which don't fit well in the genus Glossodoris, having a Chromodoris-like wide radular ribbon and body shape. So if the food does turn out to be non-thorectid it may be more evidence to show that the genus Glossodoris needs splitting up.  With your earlier posts, you and Dave have given us much valuable information on the biology of this species.

Best wishes,
Bill Rudman

Dear Gary,

Thanks for this great series of observations on the development of Glossodoris vespa. I am sorry I wasn't able to post them immediately but they are a very valuable record. Concening your question about whether the weight of the eggs affected the way the embryos were arranged in the egg capsule I think it is probably the weight of the viscera and the current caused by the ciliated velar lobes which had more affect on the way the embryos were sitting. I must admit from my experience the embryos tend to revolve a lot in the capsules, but as direct developers reach hatching time they lose the velar lobes and get a bit big for moving in their capsule.

As a general rule I think we can say direct developers have a restricted geographic range but as I discussed earlier [message #21049] there are exceptions.

Best wishes,
Bill Rudman

Thanks Gary,

Bill Rudman

Dear Gary,

Another interesting post. Opisthobranch eggs can develop in a number of different ways. The most primitive way, and probably the most common is what is called planktotrophic in which the fertilised egg begins to divide and develops into a shelled veliger larvae with large wing-shaped velar lobes. This veliger larvae hatched out of the egg capsule and swims away, feeding on one-celled algae for a time before settling out of the plankton and turning into a microscopic crawling slug.  A second type of development is called lecithotrophic and in this case a swimming veliger larvae emerges from the egg capsule, but does not feed in the plankton, and spends only a few hours to days in the plankton before turning into a small slug.

The third development type is called direct development because the embryo turns into a crawling slug within the egg capsule and hatches out as a small crawling slug. There is a whole range of direct developers from those which shpw no real sign of a veliger larvae in the grwth of the embryo to others which go through a recognisable veliger stage in the egg capsule before dropping the shell and turning into a slug all within the egg capsule.

I previously referred to Nerida Wilson's paper where she reports the development of Glossodoris vespa  as ametamorphic direct which means that the embryo doesn't develop into a recognisable veliger larvae in the egg capsule before turning into a crawling slug. 'Ametamorphic direct' is a term given to species in which there is little sign of a veliger stage. However the A structures in your drawing are velar lobes, so they are quite a bit larger than I would expect in a species with ametamorphic development. However they don't seem to have long cilia along the edge so we can probably call them vestigial. Labelling development types is difficult because there are always species which straddle the border between one type and another.

I am not sure of all the structures you have labelled but here is my best guess:

A, velar lobes
B, I guess this is the white structure in your photos. I suspect this is the larval kidney - a temporary structure lost after hatching.
C, This is probably the larval shell. In direct developer it is often reduced to a semispherical cap.
D, the body.
E, this is the larval foot.

I hope the larvae stay healthy until they hatch. It could be another couple of weeks before they do. I am not sure how you are keeping the egg ribbon but it may be an idea to change its water regularly.

• Wilson, N. G. (2002). Egg masses of chromodorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia). Malacologia, 44(2): 289-305

Good luck,
Bill Rudman

Dear Gary,

Thanks for keeping us up to date with the development of these eggs. What you are calling the yolks are in fact ther embryo - its starts as a fertilised egg and then through cell division gradually develops as an multicellular embryo. In slugs with planktonic veliger larvae the embryo develops into a shelled veliger larva which hatches out of the egg capsule and swims away. In G. vespa the embryo develops into a small crawling slug so if we are lucky you will be able to see and photograph baby slugs hatching out. The only problem is we still aren't clear on what this species eats. Unless you can discover that before the babies arrive then I am afraid they will starve.

Best wishes,
Bill Rudman

Dear Gary,

Thanks very much. This egg mass fits Nerida Wilson's report so its very good to get some illustrations of it. She reports the development to be ametamorphic which means the larvae, as they develop, don't go through a veliger stage. The egg just begins to divide and gradually develops directly into a small crawling slug. Its interesting to see an example of an egg ribbon in which the  ribbon slopes inwards.

Best wishes,
Bill Rudman

Dear David,
Thanks very much. You are probably correct in thinking I won't be able to get the sponge identified. I must say I used to think sponges were very good at keeping themselves clean of growths, and some certainly are, but unfortunately some of the main food choices of chromodorids seem to have evolved the ability to cope with being almost completely overgrown.

At the risk of seeming greedy, it would be nice to see a photo of this species' egg ribbon. As far as I know the only record is Nerida Wilson's report (2002) of a single egg ribbon, with whitish cream eggs, from the Gneering Shoals.

You are probably right in suggesting its direct development has restricted its geographical distribution, but there are some amazing exceptions to the rule that direct development means restricted distributions. One that comes to mind is Vayssierea felis which is a small species with a large Indo-West Pacific distribution. However this anomaly can be explained by its habit of living on floating algae which means the eggs rather than the larvae can be moved large distances. Another more spectacular example is the bright red sea anemone, Actinia tenebrosa, which is found all around New Zealand, and temperate Australia, and as far north as Shark Bay on the west coast and Heron Island on the east coast. Its main means of reproduction is to bud off small clones which pop out of its mouth to form a little cluster of babies on the rock around the parent. You can't get much more direct than that. One would expect populations to be genetically isolated, but a number of comprehensive studies suggest there is as much genetic variability as you would expect in a species with planktonic larvae. I don't know what it all means other than to be cautious of saying direct development always means a restricted distribution.

• Wilson, N. G. (2002). Egg masses of chromodorid nudibranchs (Mollusca: Gastropoda: Opisthobranchia). Malacologia, 44(2): 289-305

Best wishes,
Bill Rudman

Dear Gary,
Thanks for some more photos of this species which certainly seems to be found only in southern Queensland. I must say your comment that it is pretty common interests me. Perhaps you could keep an eye out for one laying eggs or even better - eating a sponge.

Best wishes,
Bill Rudman

This is Glossodoris vespa which is at present only known from southern Queensland. It is quite similar in shape and anatomy to Glossodoris cincta, but its colour pattern is quite unique. I named it "vespa" which is "wasp" in Latin because of its black and yellow colour.