Alarm cues are produced by an organism when injury occurs, and serve to signal danger when detected by conspecifics or to attract other predators that may disrupt the predation event. We exposed aquatic isopods (Caecidotea intermedius) and amphipods (Crangonyx setodactylus) to chemical stimuli from macerated conspecifics to test for the presence of alarm cues in these taxa. Three variables were examined during this experiment: time spent moving, time in refuge, and time in open. Despite previous evidence for the presence of alarm cues in both taxa, we found that only amphipods responded to alarm cues by decreasing overall movement. Isopods did not display any differences in behavior following exposure to alarm cues, which may be due to degradation of the active compounds in the alarm cues due to preparation and not the absence of these cues in general.

No abstract

Learning is crucial to the survival of organisms across their life span, including during embryonic development. We set out to determine when learning becomes possible in amphibian development by exposing spotted salamander (Ambystoma maculatum) embryos to chemical stimuli from a predator (Ambystoma opacum), nonpredator (Lithobates clamitans), or control at developmental stages 16–21 or 36–38 (Harrison 1969). Once exposures were completed and embryos hatched, we recorded the number of movements and time spent moving of individuals in both groups and all treatments. There was no significant difference in number of movements or time spent moving among any of the treatments. The groups that were exposed to predator stimuli and a blank control at stages 36–38 were also tested to determine whether there was a difference in refuge preference or difference in survivorship when exposed to a predator (marbled salamander). There was no difference in survival or refuge preference between individuals; however, all individuals preferred vegetated over open areas regardless of treatment type. We discuss hypotheses for the absence of embryonic learning in this species and suggest it may be the result of the intensity of the predator–prey interaction between the predator, large marbled salamander larvae, and the prey, spotted salamander larvae.