Influence of lowered salinity and elevated cadmium on the survival and metamorphosis of trochophores in Capitella sp I

It is well known that the competent larvae of many marine invertebrate spec ies can be stimulated to metamorphose by exposing them to elevated concentr ations of certain ions, neuroactive substances, and pharmacological agents. In this study we report that larvae of the euryhaline polychaete Capitella sp. I are induced to metamorphose within 24-48 It by reducing salinity fro m 30 parts per thousand to 12-15 parts per thousand. At 10 parts per thousa nd, however, fewer larvae metamorphosed and the normal metamorphic response to sediment was inhibited; competence was restored within 3 h or transferr ing the larvae back to full strength seawater (30 parts per thousand). Larv ae also metamorphosed within 24 h in response to increased external cadmium concentrations of 1000-2000 mug l(-1). Further understanding of how reduce d salinity and elevated cadmium stimulate (or inhibit) metamorphosis may le ad to a better understanding of signal perception and transduction ill this and other species.