Recruitment in the intertidal limpet Lottia digitalis (Patellogastropoda: Lottiidae) may be driven by settlement cues associated with adult habitat

The ribbed limpet, Lottia digitalis, is found high in rocky intertidal habitat throughout its geographic range. In order to identify likely natural settlement locations for larvae of this species, laboratory-reared larvae were settled onto substrata collected from within and near an adult L. digitalis habitat. Of larvae exposed to rock chiseled from within high-intertidal adult habitat, 31.0% and 23.3% underwent metamorphosis during two separate experiments. Similarly, an unidentified filamentous green alga that was isolated from this rock induced metamorphosis in 26.6% and 8.7% of larvae during additional experiments. In contrast, larvae did not metamorphose upon bare rocks or upon rocks encrusted with a crustose corraline alga (CCA) that were collected from lower intertidal zones, nor did they metamorphose upon the macroalgae Ulva sp., Enteromorpha contorta, Alaria marginata, or Polysiphonia sp. The presence of mucus from adult conspecifics during these experiments did not enhance metamorphosis onto rock taken from adult habitat, but it did induce metamorphosis in an average of 13.5% and 7.0% of larvae introduced to the mid-intertidal bare rock and CCA substrata, respectively. Finally, 38.0% and 34.4% of larvae from two experiments underwent metamorphosis when exposed to the high-intertidal barnacle Pollicipes polymerus. These results suggest that larval settlement, rather than differential post-settlement mortality and/or migration, drives recruitment of L. digitalis in high-intertidal habitats.