Field verification of chondroitin sulfate as a putative component of chemical alarm cue in wild populations of fathead minnows (Pimephales promelas)

Abstract

Chemical characterization of damage-released alarm cues in ostariophysan fishes has lagged far behind the study of the ecological role that these cues play in behavioral decision-making of prey fishes. Chondroitin sulfate has been identified as a putative component of alarm cue based on two laboratory studies of zebrafish, Danio rerio, and the northern studfish, Fundulus catenatus. The fathead minnow, Pimephales promelas, is a model organism in the study of chemically mediated predator–prey interactions, in part because they can be studied in the laboratory and under field conditions. Here, we conducted a field experiment on wild populations of fathead minnows, to test for area avoidance of chondroitin sulfate relative to conspecific skin extract (containing alarm cues = positive control) or water (negative control). We repeated the experiment in two small lakes in central Minnesota using minnow traps containing blocks of sponge with one of the three test cues. We found that fathead minnows avoided traps chemically labeled with conspecific alarm cue more than control traps labeled with water, and that the number of minnows caught in traps labeled with chondroitin sulfate was intermediate between alarm cue traps and water traps. These data are consistent with laboratory findings that chondroitin sulfate is a component of alarm cue, but that other species-specific compounds are needed for a full behavioral response.