The importance of body size in the subtidal ecology of Norrisia norrisii (Sowerby) (Gastropoda: Prosobranchia)

Summary

In a resource-limiting situation, larger individuals exhibited more specialized habitat selection. The preference of both small and large Norrisia for seasonally stable algae indicated the importance of epiphytic film quality. When transplanted to a suboptimal habitat, large Norrisia climbed upward consistently more often than small snails, thereby encountering food-rich substrates. Downward movement enabled small snails to avoid risks associated with surge, while diversifying their array of potential food sources. Upwardly biased large snail dispersal persisted in the laboratory except in the absence of light, suggesting a phototactic origin for this bias.