Re: J.E.Austin's Hypselodoris zebra query

November 9, 1998
From: Bill Rudman

I have split J.E.Austin's question(s) into separate topics .. Bill Rudman. This is on Hypselodoris zebra

Dear Dr. Rudman:
....... I have been watching Hypselodoris nudibranchs that were gathered outside the Bermuda Biological Station. They sit in my flow-through tank and have laid ribbons with red eggs. Some of them have little purple nodules beneath the side flaps of tissue. They are beautiful and hungry, I think. ......

You mention in Rudman, W.B. 1991, [Further studies on the taxonomy and biology of the octocoral-feeding genus Phyllodesmium, Ehrenberg, 1831 (Nudibranchia: Aeolidoidea). J. Moll. Stud. 57: 167-203], that Chromodorids can concentrate anti-feedants from consumed sponges. Has this been assayed in Hypselodoris zebra? This orange, blue-striped dorid found in Bermuda feeds on the purple sponge Dysidea etherea?. I have 6 specimens and would like to try something, any suggestions?

The paper makes reference to Rudman 1984, but I could not find the reference at the end and was wondering if you have that citation?

Thank-you for your time,
J.E. Austin

I think the "little purple nodules beneath the side flaps of tissue" you describe are mantle glands, which are characteristic of chromodorids. Each genus has a different arrangement of these glands. Have a look at the photosof Chromodoris woodwardae and Mexichromis macropus.

As luck would have it I have just discovered a student review The Sequestering of Secondary Compounds from Sponges by Nudibranchs by Tim Judd, Colorado State University ,which has been recently posted. He refers to a fairly recent study (Grode, S. H., J. H. Cardellina II. 1984) on H. zebra and food sponge chemicals.

You ask what you can do with six specimens. I presume you mean while they are still alive? It seems they feed on the sponge Dysidea so food choice experiments would seem a bit of a waste of time. What we really need is some good behavioural experiments to show that fish find them distasteful, and associate the bad taste with particular colour patterns. What you need on hand is a good behavioural scientist who can help you set up a proper experimental regime.

Going from the sublime to the ridiculous. I am not sure whether Hypselodoris zebra has planktotrophic larvae, lecithotrophic larvae or direct development.
Perhaps if you have access to clean sea water you could keep some egg-masses alive and see whether the young hatch as veliger larvae or as crawling young. Without the proper equipment actually measuring egg and embryo diameter to get some idea of development type may be too difficult.

What would be nice, and this goes for many species is to get a better idea of the range of colour variation is found within a population. If you can find more specimens and a range of size, it would be useful to record the colour patterns, and which parts of the pattern seem to be constant in all specimens etc.

The last part of your question about Rudman 1984. That is the chromodorid generic review paper in which I describe the the mantle glands.

References: Grode, S. H., J. H. Cardellina II. 1984. Sesquiterpenes from the sponge Dysidea etheria and the nudibranch Hypselodoris zebra. Journal of Natural Products 47(1):76-83.

Rudman,W.B.,1984. The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: a review of the genera. Zoological Journal of the Linnean Society, 81: 115-273.

Best wishes.... Bill Rudman

Rudman, W.B., 1998 (Nov 9). Comment on Re: J.E.Austin's Hypselodoris zebra query by Bill Rudman. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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