Re: Brittle stars and nudibranchs

February 12, 2000
From: Gordon Hendler

Dear Mary Jane,
Bob Bolland alerted me to your question about brittle stars in "Sea Slug Forum." I checked the site, and admired both your photographs and your curiosity.

I can't answer your question with precision, but I can relate a couple of points that might be of interest. There are a fair number of brittle star species that live in association with sponges and various kinds of corals. In some cases the relationship is very specific, and in other cases the
brittle stars are not particular about their hosts. There is evidence that some associations could be mutually beneficial (commensal). There are many fewer instances reported of brittle stars that "hitch a ride" on mobile species, but some brittle stars are known to ride from place to place on sea urchins and even on jellyfish.

I cannot identify the brittle stars that you photographed on Notodoris, but I can tell you that brittle star phoresy on nudibranchs has not been reported in the echinoderm literature. It would be well worthwhile to photograph and any similar instances in the future, make detailed notes on the behavior of the animals, and collect specimens of the brittle stars that occur on the nudibranchs and on the sponges that the nudibranchs crawl across. Small, delicate brittle stars such as the ones you photographed are best preserved in alcohol.

Many brittle stars have planktonic larvae, which provide an effective dispersal stage early in the life cycle. Other species, some of which associate with corals, have benthic, crawl-away young. We are just beginning to learn about the varied and interesting ways that post-larval brittle stars migrate. Along those lines, you may be on to something interesting. I'd be grateful to hear what you find in the future.

Sincerely,
Gordon Hendler
Curator of Echinoderms
Natural History Museum of Los Angeles County.

Hendler@nhm.org

Hendler. G., 2000 (Feb 12) Re: Brittle stars and nudibranchs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1886

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