MEPS 329:307-310 (2007)  -  doi:10.3354/meps329307

ABSTRACT: The chemical defense of the Caribbean octocoral Pseudopterogorgia americana was investigated using feeding assays performed in aquaria and in situ with a natural assemblage of predatory fishes. Using a bioassay-guided scheme, crude extracts, fractions and pure compounds were incorporated into palatable foods and tested. Only the secosterol fraction deterred fish feeding. Two secosterols were identified from the bioactive fraction by spectroscopic methods and comparison with literature data: 9,11-secogorgosterol (Compound 1) and 9,11-secodinosterol (Compound 2), both of which have been previously described from Pseudopterogorgia spp. Our results suggest that symbiont-produced gorgosterol and dinosterol are oxidized by the coral host to C-ring secosterols, which then provide a chemical defense to both coral and alga.

KEY WORDS: Gorgonaceae · Octocorallia · Pseudopterogorgia americana · Secosterols · Feeding deterrents · Chemical defense