Abstract

The behavioral responses of veliger larvae of the gastropod Concholepas concholepas were studied in the presence of different natural and artificial settlement cues and microbial films. Early pre-competent larvae stopped swimming, sank (due to ciliary arrests, retraction of the velum into the shell, or both), and remained inactive on the substratum when exposed to conspecific mucus and hemolymph. In both cases the effect was time-de- pendent and the number of larvae showing these behaviors decreased over time. Larvae exposed to NH4Cl (ammo- nium ion) showed a similar time- and dose-dependent response. A positive and time-dependent response was also observed when larvae were exposed to different ex- tracellular matrix (ECM) components (i.e., collagen, gel- atin, and fibronectin) and sulfated polysaccharides (i.e., carrageenan, heparin, and chondroitin sulfate). In this case the larvae remained attached to the substratum. However, the effect of sulfated polysaccharides on C. concholepas larval behavior was faster than that observed with other ECM molecules. We also studied the responses of pre- metamorphic C. concholepas larvae exposed to different microbial films. In chemotaxis experiments with different films, with glass as the substratum, larvae showed a sig- nificant preference for multispecific and diatoms films. When shells of C. concholepas were used as the substra- tum, the preference for multispecific films was clear and significant. Likewise, larvae showed velar contractions in the presence of all the films tested.