Parasites on Phestilla melanobranchia

November 21, 2007
From: Jon Bertsch


Leslie Harris (I think that's the name) from the Natural History Museum of Los Angeles County suggested that I send this image of Phestilla melanobrachia to you as a second record to go along with a previous image [message #9871 ] showing internal parasites on the host.

Locality: Komodo National Park, 30ft, Indonesia, Flores Sea, Pacific Ocean, June 2004, Rocky reef. Length: 3 - 4 inches. Photographer: Jon Bertsch.

Jon Bertsch

Bertsch, Jon, 2007 (Nov 21) Parasites on Phestilla melanobranchia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Jon,

and thanks Leslie. The pinkish sausage-shaped objects are egg sacs of an internal copepod [crustacean] parasite. If you consider that every copepod has a pair of these egg sacs it means that this Phestilla is keeping about 20 copepods in food! Starving opisthobranchs usually reabsorb their gonads and reproductive system, so I suspect that if we dissected this animal we would find that its ovaries would be empty. It would be interesting to know if these parasitic infestations are permanent or temporary. Does the copepod live in the nudibranch producing eggs until the nudibranch dies, or does the copepod have a short lifecycle, dying in the nudibranch after producing one batch of eggs?

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Nov 21). Comment on Parasites on Phestilla melanobranchia by Jon Bertsch. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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