Bastadin 21, a novel isobastarane metabolite from the Great Barrier Reef marine sponge Ianthella quadrangulata.

Bastadin 21, a novel tribrominated bastadin with the uncommon isobastarane skeleton, was isolated from the Great Barrier Reef marine sponge Ianthella quadrangulata. The structure was elucidated on the basis of the 1D and 2D NMR and MS data of bastadin 21 and its tetramethyl ether.

Studies of Australian Ascidians. 5. Virenamides A-C, New Cytotoxic Linear Peptides from the Colonial Didemnid Ascidian Diplosoma virens.

Three new linear cytotoxic tripeptides, virenamides A-C have been isolated from extracts of the Didemnid ascidian Diplosoma virens collected on the Great Barrier Reef, Australia. Their structures were deduced from 1D and 2D NMR spectral data and confirmed by HPLC analysis of the constituent amino acids after hydrolysis of the peptides and derivatization with 1-fluoro-2,4-dinitrophen-5-yl-L-alanine amide using Marfey's procedure.

DEFENSIVE STRATEGIES OF SOFT CORALS (COELENTERATA: OCTOCORALLIA) OF THE GREAT BARRIER REEF. II. THE RELATIONSHIP BETWEEN TOXICITY AND FEEDING DETERRENCE.

Thirty-six specimens of soft corals (Coelenterata, Alcyonacea) were tested for toxicity by exposing Gambusia affinis (Vertebrata, Pisces) to aqueous extracts of coral macerate and assessing mortality. Fifty percent of the soft coral extracts were determined to be ichthyotoxic to the fish, supporting earlier studies. In another experiment, commercial fish food was immersed in the same aqueous soft coral extracts, dried, and offered to G. affinis at three concentrations with appropriate controls. The study of feeding deterrence showed that 88% of the 36 extracts produced negative feeding responses at the highest concentration. At intermediate concentrations, 75% of the extracts acted as feeding deterrents; 48% showed detectable deterrence at lowest concentrations. Levels of toxicity and feeding deterrence, however, were not correlated; i.e., feeding deterrence was as common among non-toxic corals as among toxic ones. This finding may help to explain why some soft corals, which apparently lack toxic defense substances, do not exhibit signs of predation in the field.