Response of true limpet Patella aspera (Patellogastropoda) pediveliger larvae to a range of settlement cues

Context Settlement and metamorphosis are key processes influencing the natural recruitment and aquaculture production of aquatic organisms. Recruitment requirements in limpets (Patellogastropoda) are mostly unknown, because of the lack of reliable settlement inducers. Aims This study tested the reliability of different cues as settlement inducers for competent larvae of the economically valuable Patella aspera. Methods Natural crustose coralline algae (CCA) and biofilms of the benthic diatom Navicula salinicola were tested as positive controls. The following four pharmacological agents were tested as chemical inducers in a wide range of concentrations: gamma-aminobutyric acid (GABA), acetylcholine (ACH), 3-isobutyl-1-methylxanthine (IBMX) and potassium chloride (KCl). Settlers were identified by the velum loss and teleoconch development. Key results CCA were strong settlement cues in all the assays. Contrary to previous hypotheses, GABA was a weak inducer with a peak effect at 10−5 M. Neither the diatom biofilms nor the other pharmacological agents (ACH, IBMX and KCl) promoted the settlement response. All pharmacological agents at high concentrations influenced larval behaviour. Conclusions CCA were reliable positive controls and settlement inducers for the production of post-larvae. With regard to pharmacological agents, P. aspera showed restrictive settlement requirements that should be considered for ecological and aquaculture studies in other limpet species. Implications This method allows the study of the settlement biology of limpets. It provides a positive control and integrates animal monitoring and comparative response to other cues.