ABSTRACT
Habitat colonization by planktonic larvae is a critical factor regulating population dynamics of marine benthic invertebrates. The chemical properties of marine environments provide important cues used by larvae to select settlement sites. Our results demonstrate a clear association between presence of a dissolved chemical stimulus and rapid behavioral response by oyster larvae. Dissolved substances released by adult conspecifics cause downward-directed swimming in the water column and attachment to substratum by larval oysters (collectively defined herein as “settlement”). As indicated by natural products chemistry and laboratory behavioral assays performed in still water and flume flow, oyster larval settlement inducers are low molecular weight (LMW) peptides with arginine at the C-terminus. Settlement by oyster larvae in response to seawater collected at field sites correlates positively with the concentration of LMW arginine-peptides. Preliminary evidence further suggests that the peptides evoking oyster larval settlement are those also eliciting metamorphosis. We are currently testing the hypothesis that adsorption of LMW arginine-peptides to exopolymers in bacterial biofilms is a key agent regulating larval metamorphosis. Chemical induction of either settlement or metamorphosis might thus be determined by the availability of LMW arginine-peptides in either dissolved or particulate form.
