Differences in feeding adaptations in intertidal and subtidal suspension-feeding gastropods: studies on Crepidula fornicata and Crepipatella peruviana.

Suspension-feeding organisms living in the intertidal zone experience reduced feeding times associated with periodic aerial exposure. The potential morphological and physiological adaptations to this reduced feeding time were investigated for two closely related gastropods, Crepidula fornicata and Crepipatella peruviana. Intertidal C. fornicata had heavier gills than subtidal conspecifics, a difference mediated by larger gill surface areas and greater numbers of gill filaments among intertidal individuals of a given size. In contrast, the gills of intertidal and subtidal C. peruviana were morphologically indistinguishable. Despite relatively larger food-collecting organs, individuals of C. fornicata from the intertidal zone had clearance rates (CR) that were not significantly different from those of subtidal conspecifics. In contrast, the CR of intertidal C. peruviana were significantly lower than those of subtidal conspecifics. The low CR of intertidal C. peruviana may be partially explained by significantly lower measured particle transport velocities across their gills. In the context of feeding, intertidal individuals of C. fornicata performed at least as well as subtidal conspecifics, resulting in a population whose adults were as large as those found subtidally. This suggests that C. fornicata has had a long interaction with the environmental heterogeneity associated with intertidal life. In contrast, intertidal individuals of C. peruviana were on average smaller than subtidal individuals and may be stressed in the intertidal. [ABSTRACT FROM AUTHOR]