Moon snails Amauropsis islandica can shape the population of Baltic clams Limecola balthica by size-selective predation in the high-latitude White Sea.

Relative importance of biotic factors (i.e., predation) in shaping community structure at high-latitude marine habitats is likely underestimated due to lack of relevant research. Size-selective predation on dominant species can strongly affect the demography of the prey resulting in indirect community-wide effects. Moon snails (Naticidae: Gastropoda) drill shells of other mollusks, and their feeding habits are thus comparatively easy to trace. Here we test the predation of the Iceland moon snail Amauropsis islandica, preying upon the Baltic tellin Limecola balthica, for size-selectivity in the high-latitude White Sea, combining caging experiments and a 17-years' survey. The results from both data sources confirm that drilled valves of Limecola are generally larger than living clams. Sizes of the drillholes on the Limecola shells in the sediments evidence that with increasing predator size its' size-selectivity shifts towards bigger prey, and larger range of sizes becomes available for consumption (0.5–7 mm range for the 2.5 mm Amauropsis and 4–20 mm for the 22.5 mm Amauropsis). In the caging experiment, larger Limecola (>8 mm length) are more likely consumed by larger predators (12.1–14.8 mm in height) than by smaller ones (7.1–8.6 mm in height). Size-selective predation by Amauropsis could shape Limecola population as evidenced by the size variation of potentially edible Limecola clams in samples with different density and size of Amauropsis. Since the large Limecola clams may have different ecological functions than small ones, Amauropsis could indirectly influence the intertidal community structure. [ABSTRACT FROM AUTHOR]