Is mating of copepods associated with increased risk of predation?

In laboratory experiments, we tested whether the cyclopoid copepod Cyclops vicinus is more vulnerable to predation by juvenile (young-of-the-year) roa ch (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 bu t significantly fewer females without eggs. Chaoborus ate similar quantitie s of pairs and females but fewer males. Pairs in copulation and egg-bearing females were detected earlier by fish than individual non-ovigerous female s or males, and pairs in copulation were captured most easily by fish. Cycl ops vicinus mated less often when Chaoborus larvae were present than in wat er in which Chaoborus was previously held, or in pure tap water. However, p redator presence or exposure to predator-treated water had no effect on (i. e. did not reduce) mating duration. Activity of C. vicinus pairs during cop ulation was significantly lower when a predator was present, or in predator -treated water, than in pure tap water, and activity of pairs decreased wit h increasing activity of the predator. Although our experiments were carrie d out under artificial conditions which cannot be transferred to the comple x conditions in the field, they suggest that mating in copepods is dangerou s and that copepods have evolved particular strategies to reduce the risk o f predation during mating.