Thanks Mike,
I think we have to consider this unanswerable. I have put your Phyllodesmium on the Forum's 'abnormalities ' page. Most records there seem to be developmental abnormalities, but some, like yours, seem to be the result of damage and faulty regrowth.

Best wishes,
Bill Rudman

Dear Michael,
As well as your close-up, I've added a couple of close-ups as well from your earlier photos. I ma pretty sure the round thing is attached to the white bit. I at first thought this was part of the reproductive system but it's in the wrong place. I am pretty sure its part of the same phenomenon that has caused the white cerata. It seems to be some aberrant regrowth after some injury. I'm sorry I can't be more specific but if I had the animal in front of me I could give it a gentle poke and prod just to get a better idea of what this structure is. All I can say is that it is abnormal and definitely isn't anything to do with feeding. You can see the head in the bottom right photo. I have ringed one of the oral tentacles. I am not quite sure why the oral tentacles are so contracted - perhaps they are sensitive to some defensive chemical the soft coral is exuding?

Best wishes,
Bill Rudman

Dear Mike,
I guess you have looked at the solar powered sea slug page, and the related topics listed there. Phyllodesmium longicirrum is one of the most spectacular of the solar-powered slugs because of its large flattened cerata, which remind me of the large solar paddles on earth-orbiting satellites. In this species the brown rings you can see on the skin of the body, the rhinophores and the cerata, are gardens of single-celled plants [zooxanthellae] which the animal obtains from the soft coral Sarcophyton, on which it is feeding in your photos. The pale whitish branching in the cerata are the ducts of the gut which take the zooxanthellae from the stomach out to these gardens. I am not sure why a few of the cerata are colourless but its seems they lack both the ducts of the gut and the zooxanthellae. P. longicirrum, like all species ofPhyllodesmium, is able to cast off its cerata [autotomy], much like some lizards drop off their tail, as a defensive strategy. They are able to regrow these cerata quite quickly. Perhaps these are some replacement cerata which for some reason were unable to regrow the branches of the gut?

Best wishes,
Bill Rudman

Thanks Mary Jane,
Many of the Solar powered sea slugs have branches of the gut forming a network of ducts throughout the body wall. In sacoglossans which store chloroplasts from their algal food branching digestive gland ducts are found in both the slugs which keep chloroplasts alive and slugs that don't. I suspect the branching developed initially as a way fro the animal to camouflage itself when in its food.

In the nudibranchs, such as Phyllodesmium, which keep zooxanthellae alive, branches of the gut in the body wall is a new development and only found in those with the zooxanthellae symbiosis. In these species all parts of the body which are not shaded from sunlight have branches of the digestive gland just beneath the skin. Clearly this is a way of maximising the use of available space for photosynthesis - just like plants arrange their leaves
Best wishes
Bill Rudman

Thanks Rich,
Yes this is Phyllodesmium longicirrum. This is the epitome of the Solar Powered nudibranch. The brown patches on the flattened leaf-like cerata are little gardens of one-celled plants - zooxanthellae - and the whitish brown branches are ducts of the digestive gland that allow the zooxanthellae to get from the stomach to the 'gardens'.
Best wishes
Bill Rudman

Thanks Paul,
I guess this is probably the same pair as in Rich's message. They are a spectacular sight - and i guess even more so when they are crawling over black sand
Bestw wishes
Bill Rudman

Thanks Mary Jane,
Its sounds an ideal place for someone to do some work on the biology of these fascinating animals. Just how much of their nutrient requirements are met by the gardens of zooxanthellae scattered through their bodies?
Best wishes,
Bill Rudman

Dear Mary Jane,
They could be P.longicirra or for that matter some other species of Phyllodesmium. Another example, if we need one, to show us how much we still have to learn about these animals.
Best wishes,
Bill Rudman

Dear Mary Jane,
It certainly looks like you caught them feeding. The only published record of feeding in this animal is from Orpheus Is, Palm Id Group, Queensland (Rudman, 1991) so this is a welcome confirmation. Thanks again for hunting through your files, it is much appreciated.

I wouldn't be surprised if other divers have seen P. longicirrum feeding, but such observations only become 'knowledge' when the world is told about it them. As I have said many times before, observations by amateurs are a valuable source of knowledge for us all, so anyone out there with slide collections - please have a look for photos of animals 'doing things'. They may not be your best photos, perhaps only half the animal is in focus, but if they are identifiable and show feeding, or mating, or egg laying, or some other behaviour, they may be an extremely valuable contribution to our knowledge.
Best wishes,
Bill Rudman

Dear Derek,
I am afraid it's just not possible to study the life of an animal by keeping it in captivity. Until you know something about its real life history in nature, then you won't know how to adequately prepare for it in captivity. I'm afraid we know very little about this species. What you find on the Forum and in references cited on the Forum, is about the limit of our knowledge. It is known to feed on the soft-coral Sarcophyton, but we don't know if it eats other soft corals. It obviously has a symbiotic relationship with zooxanthellae [see Solar-powered Sea Slug Page] but we can only guess that it gets the zooxanthellae from Sarcophyton. But we know nothing of its life span, whether it has planktonic larvae or any other aspect of its life cycle or way of life.
Best wishes,
Bill Rudman

Dear Delisse,

Your project certainly sounds interesting. To my knowledge no one has published a phylogeny, cladistic or otherwise, of the genus. In a 1991 paper I discussed some of my ideas on the evolution of the zooxanthellae symbiosis within the genus. The possibility that adaptations for this symbiosis could have occurred a number of times, as they surely have done in other nudibranchs, makes any cladistic analysis fraught with difficulties. There are few morphological characters which appear to be independent of that symbiosis (except reproductive system).

Good luck.

Perhaps you would like to share some of your results by sending a message to the Sea Slug Forum.

Best wishes,
Bill Rudman.

Rudman, W.B. (1991) Further studies on the taxonomy and biology of the octocoral-feeding genus Phyllodesmium Ehrenberg, 1831 (Nudibranchia: Aeolidoidea). Journal of Molluscan Studies, 57(2): 167-203.

Dear Monica,
These little notes on feeding are very interesting as it often the only way to build up a picture of the natural history of these animals. Any idea of the size of the nudibranchs. It would be interesting to know if P. longicirrum needs to 'top up' its stock of zooxanthellae with new recruits during its life time. Pteraeolidia ianthina appears to obtain a seed stock of zooxanthellae when it is a juvenile and then for the rest of its life breeds replacement plants from this initial stock.

best wishes,
Bill Rudman.

Erwin,
Thanks for picking up the anomaly. I should have changed P. longicirra a long time ago. When I put the Gallery up it was the accepted spelling, but as I was the one who changed the spelling, I can't blame anyone else! To those who are unfamiliar with such things, scientific names are governed by International Rules which, in the case of animals, are overseen by the International Commission on Zoological Nomenclature.

Part of the Rules tries to standardise the way names are "latinised" which is particularly difficult when most practising taxonomists have no knowledge of classical Greek and Latin grammar.

For those interested in the detail here is an explanation from Rudman (1991):
"Unfortunately Article 31 of the International Code of Zoological Nomenclature requires species-group names to agree in gender with the generic name with which it is presently combined. Adherence to this rule required me to alter the spelling of a number of well-known names in this genus. Phyllodesmium horridus, P. serrata, and P. cryptica, all based on Latin or
Latinised adjectives must end in -um. The name P.longicirra was more problematical. It could be treated as a noun in apposition and so stay unchanged, but Bergh apparently modified the ending from the correct 'longicirrus' to match the feminine gender of the original genus name, Myrrhine, suggesting that he was using the name as an adjective. For this reason I changed the ending to 'longicirrum'. The name of another species placed in Phyllodesmium by me for the first, P. briareus, was complicated. Bergh (1896) when naming this species gives no indication of why he used the name. However as one of the alcyonaceans it feeds on is from the genus Briareum, I assume that 'briareus' is to be treated as an adjectival form of that genus name. To agree in gender with the name Phyllodesmium (neuter) the name must also change to 'briareum.'"

You may think this has very little to do with biology - and it's a pain to sort out, but it's an attempt to keep order in the world of scientific names. Although we grumble about the problems, the International Code is one of the longest surviving international agreements - and on the whole, it works. Perhaps the fact that politicians are not involved, is the recipe for its success?

Reference:
Rudman, W.B. (1991) Further studies on the taxonomy and biology of the octocoral-feeding
genus Phyllodesmium Ehrenberg, 1831 (Nudibranchia: Aeolidoidea). Journal of Molluscan Studies, 57(2): 167-203.