Experiments were conducted to investigate the effect of plant energy content and the presence of secondary metabolites on the assirmlation efficiency. ahmentary tract evacuation rate, and feeding rate of the bucktooth parrotfish Sparisoma radians. Alimentary tract evacuation rate was significantly greater (ca 2 . 5~) when the fish fed on the relatively energy-poor calcareous green alga Halimeda incrassata than on the seagrass Thalassia testudinum. The greater evacuation rate of H. incrassata provided the fish the capacity to increase consumption rate to compensate for low food energy content. However, due to unpalatable secondary chemical metabolites present in H. incrassata. actual biomass consumed per unit time was less than for T testudinum. Experiments using T testudinum blades coated with H. incrassata organic crude extract showed that the secondary metabolites had no effect on the fish's assimilation efficiency or gut evacuation rate. The increased rate of H. incrassata evacuation is more than sufficient to allow compensation for lower gross energy content. S. radians can increase evacuation rate sufficiently to allow compensation for differences in available energy over the normal range for most plants consumed in nature. Studies of herbivorous fish foraging and feeding energetics must consider differences in alimentary tract evacuat~on rate and feeding rate, and the effects of secondary metabolites, in addition to the assimilation efficiency, structural defense and relative plant abundance factors usually considered.

The role of biotransformation enzymes in metabolism of lipophilic, dietary allelochemicals such as terpenoids and steroids has not been studied in marine organisms despite the significance of allelochemicals in the evolution of biotransformation enzymes and the importance of these enzymes in detoxification of anthropogenic xenobiotics. Here we report on cytochrome P450 and glutathione transferase (GST) from the digestive gland of Cyphoma gibbosum, a specialist predator that feeds on allelochemically rich gorgonian corals. Levels of these enzymes were compared from C. gibbosum collected in Belize from 4 different gorgonian prey species (Briareum asbestinum, Gorgonia ventalina, Plexaura homomalla, and Pseudopterogorgia americana). Cytochrome P450 specific content was very low and only quantifiable in C, gibbosum collected from P americana (21.4 to 27.4 pm01 mg-'1. A peak at ca 420 nm was also detected in most samples, indicative of degraded P450 or an independent, functional haemoprotein Methoxyresorufin 0-deethylase (MROD) and ethoxyresorufin 0-deethylase (EROD) were not detected in C. gibbosum. However, NADPH-cytochrome c (P4501 reductase (NCR) was detected in all samples and the specific activity ranged from 23.2 to 67.3 nmol min-' mg-' protein. Significantly higher NCR activity was detected in C. gibbosum collected from prostaglandin-rich P. homomalla. Glutathione transferase specific activity ranged from 2.76 to 4.05 pm01 min-' mg-l, ranking it among the highest ever reported (using l-chloro-2,4-dinitrobenzene as a model substrate). Significantly higher GST activity was detected in C. gibbosum collected from G. ventalina and B. asbestinum, suggesting that GST actlvity varies in response to different suites of gorgonian allelochemicals.

We quantified spatial and temporal patterns of brominated pyrrole variation in the common marine hemichordate worm Saccoglos5u5 kowaJevskii. Using fast·atom bombardment mass spectrometry we found a novel sodium sulfamate salt (C4HBr3N03SNa) of 2,3,4-tribromopyrrole (TBP) that predominated over 2,3,4-TBP (II % vs 0.6% ash-free dry wt). There was no relationship between the total amounts of the 2 compounds. The sulfamate salt was concentrated in the hepatic region (50 %), a possible site of synthesis or storage. 2,3,4-TBP was highest (1.5 'Yo) in the proboscis and tail, which are exposed to predation. No seasonal pattern was apparent for the sulfamate salt over a 30 mo sampling period. 2,3,4-TBP exhibited temporal inCTeases, possibly associated with spawning. The sulfamate salt was not detectable by GCIMS techniques, raising the possibility that sulfonati.on may be more common than realized. The sulfamate salt may serve as the non-autotoxic stable precursor to the more volatile 2,3,4-TBP.