Crustose coralline algal factors determining the success of limpet (Patellogastropoda: Patellidae) settlement: species, exposure time, area and soluble cues

Abstract

Crustose coralline algae (CCA) play a key role in invertebrate recruitment, yet their influence on the settlement of patellid limpets is under discussion. This study is aimed at resolving the role of CCA as a settlement inducer for patellid limpets, providing insight into the influence of different CCA-related factors. The larvae of the economically valuable limpet Patella candei were used as a model. Six assays were performed: (1) different CCA assemblages, (2) exposure time, (3) artificial removal of epibionts, (4) substrate area, (5) soluble cues (CCA-conditioned seawater), and (6) substrate selection in a choice experiment. Settlers were identified by velum loss and teleoconch development. Species composition of the CCA assemblages significantly influenced settlement, with a preference for Titanoderma pustulatum and combined Neogoniolithon sp. and Hydrolithon farinosum crusts. The substrates dominated by Agissea inamoena, marginal presence of CCA or which epibionts were artificially removed, were statistically similar to those in the negative control. The ratio of settlers increased until 4 days of exposure, after which it remained stable over time. The results support that CCA releases soluble cues with settlement-inducing effect on P. candei larvae, explaining why the ratio of settlers increased with substrate area. The choice experiment suggests that P. candei larvae have limited selectivity with respect to the substrate surface. In conclusion, the present study points to the relevance of CCA assemblages as settlement substrates for limpet larvae, with an impact on limpet recruitment in the wild as well as on the production of post-larvae for limpet aquaculture.