Meeting Abstract
The serpulid Ficopomatus enigmaticus, likely a native of Australia, has established populations on every continent except Antarctica. Invasive populations of this species often show two striking distributional patterns: individuals are found in dense aggregations (reefs), in low salinity habitats. A process that may be important in establishing both patterns is the expression of settlement preferences by larvae. To test the hypothesis that larvae of F. enigmaticus settle preferentially on conspecific adults, contributing to reef formation, we conducted two experiments. First, larvae were exposed to biofilmed tubes of conspecific adults or to biofilmed shell or tube of two other species. Settlement was significantly higher on conspecific tubes compared to other substrates. Second, larvae were exposed to various substrates in clean seawater or in seawater in which adult worms had been held. Adult effluent had no effect on larval settlement. Larval responses to cues associated with the tubes of conspecifics may thus be one factor important in reef formation. To test the hypothesis that larvae settle most readily in low salinities, we examined larval settlement in response to adult tubes or IBMX (a pharmacological inducer) in seawater adjusted to 5, 20, or 34 psu. Settlement was high at all salinities tested in both adult tube and IBMX treatments, suggesting that larval responses to salinity are not important in determining the local distribution of F. enigmaticus. Future work should test alternative hypotheses to explain the observed distribution of adults with respect to salinity, for example that juveniles and adults are excluded from full-strength seawater habitats by competition from fully marine species.
