Journal of Plankton Research Vol.22 no.10 pp.1977-1987, 2000
© Oxford University Press 2000
Is mating of copepods associated with increased risk of predation?
Department of Biology III (Ecology and Morphology of Animals), University of Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany
In laboratory experiments, we tested whether the cyclopoid copepod Cyclops vicinus is more vulnerable to predation by juvenile (young-of-the-year) roach (Rutilus rutilus) and/or larvae of the phantom midge Chaoborus flavicans during mating than individual adult copepods of the same species. We also tested whether C.vicinus avoided mating, displayed shorter mating times and/or lower activity when a predator (Chaoborus) was present, or when exposed to water in which predators (Chaoborus) were previously held. Fish ate the same quantity of pairs in copulation and individual egg-bearing females but significantly fewer females without eggs. Chaoborus ate similar quantities of pairs and females but fewer males. Pairs in copulation and egg-bearing females were detected earlier by fish than individual non-ovigerous females or males, and pairs in copulation were captured most easily by fish. Cyclops vicinus mated less often when Chaoborus larvae were present than in water in which Chaoborus was previously held, or in pure tap water. However, predator presence or exposure to predator-treated water had no effect on (i.e. did not reduce) mating duration. Activity of C.vicinus pairs during copulation was significantly lower when a predator was present, or in predator-treated water, than in pure tap water, and activity of pairs decreased with increasing activity of the predator. Although our experiments were carried out under artificial conditions which cannot be transferred to the complex conditions in the field, they suggest that mating in copepods is dangerous and that copepods have evolved particular strategies to reduce the risk of predation during mating.