Two new cryptic species of Asteronotus

January 20, 2003
From: Bill Rudman

Two new species of Asteronotus have been described in a recent paper by Gosliner and Valdes (2002). These two species, Asteronotus mimeticus and Asteronotus spongicolus are two more of the remarkably cryptic species we find associated with particular sponges in the tropical Indo-Pacific. In separate messages I have posted photos of them from the Great Barrier Reef. How I came to take the photos illustrates just how well these animals can camouflage themselves.

On a trip to the Australian Museum's field station at Lizard Island I was handed this strange dorid by a visiting sponge expert, Dr G. Bakus, who said he had found it on a cup sponge, Carteriospongia sp. The next day, Ian Loch, who was with me from the Museum, went looking for a colony of Carteriospongia so we could check the sponge's identity and take some photos. Ian found the correct sponge, so I put it in an aquarium with the dorid for photographing the next day. However, when I came to photograph the slug, I couldn't find it, despite diligently searching all over the sponge. Finally in desperation I started to rip the sponge into strips, hoping to find the animal that way. I finally had success, but surprisingly the slug I found was a distinctly different one which we hadn't seen on the sponge the day before. Finally I also found the original one, extremely well-hidden on the remains of the sponge, and I was able to photograph them both. I have waited for years in the hope of finding more specimens of these two amazing species. From Gosliner & Valdes's paper it seems they are widespread in the Indo-West Pacific, but it seems that their excellent camouflage has ensured that they have seldom been seen.

• Gosliner, T.M. & Valdes, A. (2002). Sponging off of Porifera: new species of cryptic dorid nudibranchs (Mollusca, Nudibranchia) from the Tropical Indo-Pacific. Proceedings of the California Academy of Sciences 53(5): 51-61.

Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Jan 20) Two new cryptic species of Asteronotus. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from