Thanks Glen,

Your question is an interesting one. The answer is complicated because firstly, as you know, these animals have a full set of male and female organs and secondly, the actual copulatory organs are in a different place when they are functioning than they are the rest of the time. To keep it as simple as possible I will just deal with Triopha, and related nudibranchs in which both male and female organs are found in much the same part of the body. When you dissect a preserved Triopha there is a genital pore on the right side of the body which opens into a small sac, which is called the genital vestibule. There are three openings into this sac, one of which is the male penial opening, and the other two are female openings, one which receives the penis of the partner, and the other which deposits the fertilised eggs in the typical egg ribbon. It's hard to call one of these the vagina, as in mammals there is a single duct which performs both these functions. So the first problem is what to call the ducts. The second problem is that things look quite different during copulation. The genital vestibule turns inside out so that what is a sac in a preserved, or non-mating animal,  is a raised 'tube' as you described, in a mating animal. The penial opening effectively disappears as a hole, because the penial apparatus which has been tucked inside the body cavity is pushed out so that it can enter the appropriate female duct of its partner.

I tend to skirt around the problem by talking about the everted genital organs or genital apparatus. There is no problem talking about the everted penis, but in species like Triopha with two female openings, calling the opening that the penis enters the vagina, leaves the 'egg duct' without a name. There are other dorids and nudibranchs in which there is only one female duct. In those cases, calling the common female duct the vagina seems perfectly appropriate. I know this doesn't give you a satisfactory answer - perhaps if you want a descriptive term to describe what you can see in the photo, ' everted mating organs' is the answer, because it could apply to nudibranchs with one or two female genital ducts.

Best wishes,
Bill Rudman

Dear Paul,
I guess one problem with animal behaviour studies is the ease with which we can transfer our emotions and behaviours to those of the animals being observed.

However if you follow the 'selfish gene' theory of evolution which proposes that the main aim of an organism is to pass on its genes to the next generation, then you would expect organisms to evolve ways of encouraging such behaviour. Whether a slug's response to various stimuli can be described as pleasure or pain is beyond me, although I am sure that as we speak there are a whole army of scientists out there with microprobes embedded in mollusc nerve cells studying such things. There is a serious side to this work however.  Dr Eric Kandel has recently received the Nobel Prize for pioneering work he did, sticking microprobes into the ganglia of Sea Hares, to develop theories on learning.

Thanks for the photos,
Bill Rudman

Dear Paul,
I would agree that it looks rather different from Triopha catalinae. It is the animal called Triopha sp. 1 in Behrens, 1991. According to Behrens (2004) Sandra Milen has looked at its anatomy and decided it is a colour form of Triopha catalinae. Specimens of this colour form are noted by Behrens from Washington, British Columbia and Alaska

• Behrens, D. W. (1991) Pacific Coast Nudibranchs. Monterey, California, Sea Challengers.  107pp.
• Behrens, D. W. (2004) Pacific Coast Nudibranchs, Supplement 2. New species to the Pacific Coast and new information on the oldies. Proceedings of the California Academy of Sciences, 55: 11-54.

Best wishes,
Bill Rudman

Thanks Bruce,
Bill Rudman

Dear Jimmy,
I guess the nudibranch you are interested in is Triopha catalinae which is found on the west coast of North America and is often called the Clown Nudibranch. As well as being found from Mexico to Alaska, it has also been found once in Japan and if you look at the other messages on the Forum, it has also been found in Korea.

We don't know much about its biology but have a look at the species' Fact Sheet for some information. Also have a look at the other messages on the Forum about this species, which are attached below your message on this page for some more information. For example the message directly below your message has a photo of one laying its egg ribbon. I am not sure if they sleep, but nudibranchs are quite often found nestled in a crevice, not moving, so I guess that could count as sleeping.
Good luck with your project
Bill Rudman

Thanks Ken,
It's good to get a photo of the egg ribbon of this species.
Best wishes
Bill Rudman

Thanks Bruce,
Bill Rudman.

Dear Marli,
I think you're right. It certainly looks like it could grow into Triopha catalinae with an extra bit of orange her and there.
Best wishes,
Bill Rudman

Dear Dong Bum,
Unless I am very mistaken this is Triopha catalinae which is a well known species in California. In North America it has been recorded from Alaska to Baja California. Baba (1957) also records it once from northern Japan. This is a very interesting find, confirming its presence in the NW Pacific.

• Baba, K. (1957) A revised list of the species of Opisthobranchia from the northern part of Japan, with some additional descriptions. Journal Faculty Science, Hokkaido Imperial University, series 6, Zoology, 13: 8-14.

Best wishes,
Bill Rudman

Thanks Ken,
By amazing coincidence both your photos and Daniel Geiger's message arrived on the same day. This beautiful animal cetainly deserves a few beautiful photos.
Best wishes,
Bill Rudman

Thanks Daniel,
It's nice to get a photo showing the body shape of a species of Triopha.
Best wishes,
Bill Rudman

Dear Marli,
Thanks again,
Bill Rudman.

Dear Ryan,
I have seen photos of Triopha catalinae and indeed it would be a beautiful animal to work with. If you have any photos, it would be nice to have one for the Forum.

Concerning cnidosacs. Have a look at the page on cnidosacs and the page on aeolid cerata. I am afraid cnidosacs are found only in some aeolid families and the 'papillae' on the back of Triopha, although they look quite similar to those of aeolids are unrelated and quite different in structure and function.

Have a look at the Species List (see button in blue bar at top and bottom of each page) and look at some of the species in the family Polyceridae, and in particular the subfamily Triophinae, for some information on related nudibranchs. They are all bryozoan feeders so one possible aspect of their biology to look at would be to see how many species of bryozoans they feed on - perhaps only one? I don't know what your time frame is, but if you have a year perhaps you could have a look at the life cycle, when they breed, what their egg ribbons look like, do they have planktotrophic larvae, how much colour variation is there?

Very few nudibranchs are so well known that all these obvious questions have been asked and answered. If you have plenty of animals there are lots of basic questions to ask. Do they stay on one bryozoan colony until they eat it out, how long does it take them to kill a colony etc, etc.

I am not familiar with any study on the biology and natural history of this species, or any of its relatives, so any information you discover would be of great interest. If anyone knows of any such study could they let us know please? If you do decide to look into Triopha, please keep us informed of your discoveries, and any photos of it or other opisthobranchs from Pedder bay would be of great interest.
best wishes,
Bill Rudman.

Dear Nicole,
In the past I have been fairly tolerant of urgent last minute requests to help with school work but don't you have at least a short break over the Xmas - New Year period? We have our summer holidays in the southern hemisphere and I am just preparing for about a month's holiday so I am afraid there is no way I can meet your deadline.

I suggest you look in a library for a good book or contact your local museum. I think the name used for Triopha carpenteri these days is Triopha catalinae (Cooper, 1863) so look for information on that species as well. Also have a look at the website Links Page for websites that deal with the west coast of North America (East Pacific).

Best wishes,
Bill Rudman.