Dear Colin,

This is certainly what has been described as R. suzanneae. Perhaps in time we will find that two species may be just extremes of a colour range. Similarly, it is much too early to be precise about geographic ranges of species and their depth distributions. In many cases we have information for very few specimens of each species. That's why records like yours and other Forum contributors are so important - they are enabling us to flesh out the details on colour variation, geographic distribution, and aspects of a species natural history, which are often sadly missing from new species descriptions.

Best wishes,
Bill Rudman

Dear Marina,
Thanks for these photos. I am glad you mentioned you had moved the animal in the middle photo onto that sponge as I was going to include a close-up of the sponge as a possible food. Where possible, it is best if you are re-positioning animals to try and put them somewhere 'neutral' like on a piece of rock. Apart from the problem of adding misleading information, many animals react badly to being put on a sponge or cnidarian colony they are not familiar with and so are difficult to photograph. They may in fact be being stung or affected by defensive secretions being produced by the 'photogenic' colony you have selected.

Concerning defensive secretions in phyllidiids. Most genera produce rather nasty chemicals called sesquiterpene isocyanides. There can be toxic and acidic. I walked into a closed lab one morning where overnight a number of have been kept in an aquarium. The air was so acrid and full of these chemicals that I could hardly breathe and by eyes were stinging and watery. I only stayed long enough to open windows etc to try and clear the air. Everything else in the tank was dead.

Concerning what is an allomone. You will have heard of a hormone which is the name we give to chemical substance which an animal uses internally to communicate or send signals to other parts of its body. A whole set of words of been derived from 'hormone' to label other chemical signals.

• pheromone - a chemical substance produced by a species to communicate externally with other members of the same species. [affecting the behaviour or physiology of the same species]
• allomone a chemical substance produced by a species to communicate externally with members of different species. [affecting the behaviour or physiology of another species]

Unfortunately some people feel the need to try and define and name every alternative phenomenon and I am afraid they are at present attempting to narrow the definition of allomone. When it was first proposed its meaning was as I have stated above “a chemical substance released by one species that serves as a communicative
signal to another species”. You should be aware that some people have a much narrower definition:
• allomone Compound produced by one organism that affects, detrimentally, the behaviour of a member of another species.
• kairomone Compound produced by one organism that affects, beneficially, the behaviour of a member of another species, but hurts the animal that produces it.
• synomone Compound produced by one organism that is beneficial to both itself and a member of another species.

Personally I find life becomes unnecessarily complicated when some of out colleagues feel the need to pigeon-hole natural phenomena so minutely.
Best wishes
Bill Rudman

Dear Valeria,
Thanks for this interesting find. Phyllidiids are not my favourite group to try an identify from photos because we still a lot to learn about them so it is never easy to be sure. However a few of them are quite easy and that includes this one, which has only recently been named. This is Reticulidia suzanneae. Most records are from Thailand, but there is a message on the Forum from Bernard Picton, with a photo of a specimen from Pemba Island, which is not that far up the east African coast from Comoros.
Best wishes,
Bill Rudman

Thanks Bernard,
I have just got a message today informing me that this species is now named Reticulidia suzanneae. Nice to be able to increase its known geographical range so quickly.
Cheers,
Bill Rudman

Thanks for keeping the Forum up to date on new names. I am just posting a message from Bernard Picton today increasing this animal's distribution to the western side of the Indian Ocean.
Cheers,
Bill Rudman

Dear Erwin,
This is an unnamed species, almost certainly a Reticulidia, which has already been reported on the Forum from Thailand as Reticulidia sp. 1

Dear Narongpon,
You are quite right. If it has the gills underneath the mantle as you describe it is clearly not Halgerda.

Thanks for the second photo. Certainly no sign of a gill pocket. Your animal is an unnamed species of Reticulidia, Reticulidia fungia and Reticulidia halgerda being the only two described species.

For those of you unfamilar with the gills in phyllidiids I have included here a photo showing the secondary gill leaflets of Phyllidia ocellata which, like all phyllidiids, form a band down each side of the body beneath the mantle skirt.

Best wishes,
Bill Rudman.

Dear Narongpon,
In a photo it's a bit difficult to be sure, but I think this is a species of Halgerda with the gills retracted into the gill pocket, rather than a species of Reticulidia, which like all phyllidiids, would have no dorsal circlet of gills.

If it is a Halgerda I think it is an unnamed species. Not many species have been described with a white line along the mantle ridges.

Halgerda xishaensis Lin, 1975, is brown with white ridges and dark brown 'knobs' or tubercles at the junction of the ridges.

H. dalanghita has a pale whitish line edged in brownish spots, and H. albocristata has secondary white lines radiating out from the tubercles. It also has a white border with black lines at right angles to the mantle edge.

None of these species have large black or dark spots in the 'valleys' as in this animal from Surin Island. It is an interesting find Narongpon. It looks quite similar to Halgerda sp. 4. from Kerama Island, but that animal was probably a juvenile, so it hard to compare them.

Best wishes,
Bill Rudman.