Effects of competition and predation on the feeding rate of freshwater snails

Foraging behavior of snails is affected by competition and risk of predation, which can be detected by chemical cues in the water. Freshwater snails are able to detect and respond to kairomones, from predators, and chemical cues, such as alarm cues, from other snails. Invasive species, such as the Chinese mystery snail, are known to affect native species through processes such as competition and predation. This study examines the effects of different chemical cues on the feeding rate of Helisoma trivolvis. The different chemical cues involved in this study include kairomones, alarm cues from crushed conspecifics and from crushed invasive snails, and chemical cues from intraspecific and interspecific competitors. This study also looks at the effects of different densities of competitors and crushed snails on the feeding rate. Higher densities of competition cause the snails to increase their feeding rate compared to no competition and low densities. There is a trend for interspecific competition to cause higher feeding rates than intraspecific competition. Presence of crayfish causes the snails to decrease their feeding rate and it masks the effects on density and type of competition on the feeding rate. There is no significant difference in feeding rates for the different treatments between the predation and crushed snails experiments, suggesting kairomones are more influential than alarm cues in altering foraging behavior. Despite significant effects of Chinese mystery snails on the feeding rate of H. trivolvis, the invasion of Chinese mystery snails is likely to alter the community structure by consuming more algae and possibly increasing the feeding rate of native snails.