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

Abstract

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, Acanthaluteresspilomelarnurus (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 suggestamathamides serve as chemical defences of A. wilsoni. Because bryozoans are often colonised by epibionts, we also examined representativesof the epizoic community on A. wilsoni , using gas chromatography! mass spectrometry (GCMS) for the presence of amathamides. Of 34epizoic species tested, only one, the sea spider Stylopallene longicauda Stock which was present in high average densities, containedamathamides in concentrated amounts even when deprived of food for 36 hours. In view of the demonstrated feeding deterrence ofamathamides in bryozoans, the relatively high epizoic density of S. longicauda and its apparent aposematic colouration suggest thatamathamides may also function as chemical defences for S. longicauda.