Meeting Abstract
Predators have been widely demonstrated to influence the developmental plasticity of prey. For example, crustacean amphipods may attain smaller body size and associate with structure to reduce predation by visual fish predators. However, to date, no studies have investigated the role of conspecific cues on the induction of an individual’s anti-predator response. The present study investigated the growth of individual and groups of juveniles of the freshwater amphipod Hyalella azteca chronically exposed to chemical cues from a sympatric sunfish predator (Lepomis megalotis). Amphipods were placed in containers either individually or in groups of three and exposed to sunfish chemical cues or a control for 30 days. On day 35, amphipods were further tested for behavioral responses to a structural refuge following acute exposure to sunfish cue. Image analysis revealed that individuals held in groups chronically exposed to sunfish cue attained body sizes that were significantly smaller than amphipods in groups chronically exposed to controls. However, solitary individuals exposed to sunfish cue did not differ significantly in size to controls. Behavioral trials revealed that pre-exposure to sunfish cues had no significant effect on use of structural refuge. To test if the reduction in size seen in the grouped amphipods exposed to sunfish cue was due to a conspecific chemical cue, individual amphipods in opaque bottles were placed into containers containing three or no amphipods and exposed to sunfish cues or control for 30 days. The bottle openings were covered with mesh to only allow for the passing of sunfish and conspecific chemical cues. The results will be interpreted based on our hypothesis that individuals require conspecific cues in combination with sunfish cues to induce a plastic response to reduce predation.
