Amathamide alkaloids in the pycnogonid, Stylopallene longicauda, epizoic on the chemically defended bryozoan, Amathia wilsoni

Amathamides comprise a group of brominated alkaloids found in the bryozoan, Amathia wilsoni Kirkpatrick (Gymnolaemata: Ctenostomata). We tested a crude bryozoan extract and purified amathamide C for their ability to deter feeding by fish, Acanthaluteres spilomelarnurus (Quoy and Gaimard, 1824 ) (Leatherjacket), in laboratory assays. Food pellets made with crude extracts (1 % dry weight) caused 94% inhibition of artificial pellet acceptance, while amathamide C at 0.1 % dry weight caused 86% inhibition. These results suggest amathamides serve as chemical defences of A. wilsoni. Because bryozoans are often colonised by epibionts, we also examined representatives of the epizoic community on A. wilsoni , using gas chromatography! mass spectrometry (GCMS) for the presence of amathamides. Of 34 epizoic species tested, only one, the sea spider Stylopallene longicauda Stock which was present in high average densities, contained amathamides in concentrated amounts even when deprived of food for 36 hours. In view of the demonstrated feeding deterrence of amathamides in bryozoans, the relatively high epizoic density of S. longicauda and its apparent aposematic colouration suggest that amathamides may also function as chemical defences for S. longicauda.