The Influence of Chemical Stimuli from Predators on Precopulatory Pairing by the Amphipod, Gammarus pseudolimnaeus

Authors

  • Alicia Mathis,

    Corresponding author
    1. Department of Biology, Southwest Missouri State University, Springfield
      Department of Biology, Southwest Missouri State University, Springfield, Missouri 65804-0095, USA. E-mail: sam477f@uma.smsu.edu
    Search for more papers by this author
  • W. Wyatt Hoback

    1. Department of Biology, Southwest Missouri State University, Springfield
    Search for more papers by this author

Department of Biology, Southwest Missouri State University, Springfield, Missouri 65804-0095, USA. E-mail: sam477f@uma.smsu.edu

Abstract

Many amphipod crustaceans exhibit precopulatory mate guarding. Field samples of the amphipod Gammarus pseudolimnaeus indicated that pairs were positively size assortative. Receptive individuals readily formed pairs in the laboratory and the latency to formation of precopulatory pairs was decreased under threat of predation. In addition, females and, under conditions of extreme danger, males that formed pairs were significantly smaller when under the threat of predation. Amphipods distinguished between chemical stimuli (aquarium water) from predatory and nonpredatory fishes and between chemical cues from fish predators (trout) that had recently eaten conspecific amphipods vs. those fed a control diet of pelleted commercial fish food. These data indicate that chemical stimuli associated with predators can influence reproductive behavior of amphipods. The results also suggest the hypotheses that: 1. search time may be costly in terms of probability of predation; and 2. small pairs may be safer from predation than larger pairs.

Ancillary