Variable mating durations in cyclopoid copepods: An adaptation to changing predation risks?

Abstract

Investigation of the mating patterns of three species of freshwater plank-tonic cyclopoid copepods (Cyclops vicinus, Mesocyclops leuckarti and Thermocyclops crassus) showed that mating behaviour, especially mating duration, depends upon ambient light conditions and sex ratio. Species which lived in upper water layers (Mesocyclops leuckarti, Thermocyclops crassus) mated more quickly than the species which lived in deeper water (Cyclops vicinus). In Cyclops vicinus, mating duration was longer in darkness compared to the light. Since a prey is more vulnerable to predation by visually hunting zooplanktivorous fish when ambient light light levels are high, the present results imply that the reduced mating duration in upper water layers or high light levels is a response to increased predation risk. In male biased trials the mate guarding phase lasted longer than in female biased trials. Thus mate guarding seems of significance in cyclopoid copepods, although re-mating is rare in this group.