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Marine Ecology Progress Series

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MEPS 207:69-77 (2000)  -  doi:10.3354/meps207069

Triterpene glycosides defend the Caribbean reef sponge Erylus formosus from predatory fishes

Julia Kubanek1,2, Joseph R. Pawlik2,*, Tegan M. Eve1, William Fenical1

1Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093-0204, USA
2Department of Biological Sciences and Center for Marine Science, University of North Carolina at Wilmington, Wilmington, North Carolina 28403, USA
*Corresponding author. E-mail:

ABSTRACT: The reef sponge Erylus formosus (Demospongiae: Geodiidae) from the Bahamas and southern Florida contains a suite of triterpene glycosides that, at a natural volumetric concentration, deters predation by the fish Thalassoma bifasciatum in laboratory assays, and a natural assemblage of reef fishes in field assays. Antifeedant metabolites were isolated by bioassay-guided fractionation of extracts of E. formosus using standard chromatographic methods and identified by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. Included in the deterrent mixture from E. formosus collected in the Bahamas and Florida were at least 6 related triterpene glycosides possessing identical aglycones but with different sugar residues. Two additional compounds with a penasterol triterpene core (formoside, and an N-acetyl galactosamine derivative, formoside B) were found in specimens from the Bahamas but not Florida. Formoside, while being the major deterrent metabolite of E. formosus from the Bahamas, is less potent than the other triterpene glycosides on a weight per volume basis. As a mixture, the triterpene glycosides protect E. formosus from predatory reef fishes, but when these compounds were separated into fractions some failed to deter feeding at natural concentrations. As compounds of this type are beginning to be recognized as prevalent sponge metabolites, we suggest that terpene glycosides may have important ecological functions, just as a defensive role has been ascribed to similar compounds in sea stars, sea cucumbers, and terrestrial plants.

KEY WORDS: Sponge · Coral reef · Caribbean · Chemical defense · Predation · Triterpene glycosides · Erylus formosus · Formoside

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