Professor P.R. Bergquist

September 14, 2009
From: Bill Rudman

In one of today's messages [#22658 ] the topic is Halisarca laxus (Lendefeld), a pink sponge, which lives commensally on ascidians, and is the preferred food of Hallaxa michaeli. The identity of the sponge, remained a mystery for over 100 years until a living specimen was examined by Pat Bergquist. She also observed that it seemed to grow commmensally on the ascidian Pyura. Like Hallaxa michaeli, many species of nudibranchs have extremely specific food requirements, and the key to the study of their natural history is the ability to accurately identify their food. Unfortunately, finding experts who are willing and able to do so is very difficult. Professor Bergquist DBE, D.Sc., FRSNZ was one such expert.

Sadly, Pat died last week. She will sadly missed by her family and friends, and as a leading expert on sponge biology and phylogeny her passing will leave a gap which will be hard to fill. I first met Pat when I attended her classes at the University of Auckland, NZ nearly 40 years ago, and we have remained friends and colleagues ever since. Fortuitously the sponge groups which she was most interested in are the very groups which are the desired food of chromodorid nudibranchs, which I am interested in. She was also a pioneer in researching the chemical metabolites of sponges, showing that many phylogenetic branches have their own unique metabolites. These same metabolites are re-used by their nudibranch predators and it seems they can be re-used  as indicators of nudibranch phylogeny as well.

Without her enthusiastic and knowledgeable participation, our review of chromodorid feeding (Rudman & Bergquist, 2007) would not have been possible. It was exciting to see patterns emerging, how each chromodorid genus could be linked to particular sponge genera, but it was also exciting to see how anomolous groupings could now be explained. For example we could show that a group of Chromodoris species eating the 'wrong' family of sponges confirm that the genus Chromodoris is polyphyletic, and that a species of Glossodoris eating the 'wrong' sponge was evidence that the sponge genus Hyattella should be moved from the family Spongiidae to the Thorectidae. This may sound like esoteric minutae, but evolution occurs at this level, and if we are ever going to understand how our environment works this is a level that cannot be ignored

Thank you Pat.  

• Rudman, W. B. & Bergquist, P. R. (2007) A review of feeding specificity in the sponge-feeding Chromodorididae (Nudibranchia: Mollusca). Molluscan Research, 27(2): 60-88

Bill Rudman

Rudman, W.B., 2009 (Sep 14) Professor P.R. Bergquist. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22659

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