Effects of competition and predation on the feeding rate of the freshwater snail, Helisoma trivolvis.
Foraging behavior of snails is affected by competition and risk of predation, both of 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 (Cipangopaludina chinensis), are known to affect native species through competition and predation. This study examines the effects of competition and predation risks on the feeding rate of Helisoma trivolvis. Higher densities of competitors cause the snails to increase their feeding rate compared to no competition and low densities of competitive organisms. Presence of crayfish predators causes the snails to decrease their feeding rate and masks the effects of competitor density and type on the feeding rate. This study found 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 the 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.