Predation cues do not affect the induction and termination of diapause in small-bodied cladocerans

1. Prey usually benefit from the early recognition of potential predators by changing their behaviour, morphology and life history. Some cladocerans even shift from the production of parthenogenetic to resting eggs when facing the risk of predation. This would be particularly beneficial if resting eggs could detect predation risk and hatch appropriately. 2. Here, we evaluated the responses of small-bodied, tropical cladocerans to fish kairomones and alarm signals. Life-history changes (including the production of resting eggs) in active females of Moina and the hatching responses of Moina and Diaphanosoma resting eggs were evaluated in the presence of predation cues. 3. Predation cues did not induce diapause in Moina. However, active Moina females reacted to the presence of fish by changing other life-history parameters. The net reproductive rate of Moina increased in the presence of predation cues, clutch size increased, and neonates were released earlier, but the size at primipara was less (under low food conditions). 4. Resting eggs from lake sediments were not sensitive to fish cues, as hatching rates and the time to hatching were not affected. So, hatchlings may face a dangerous environment. 5. The life history of active individuals clearly responds to fish in an adaptive way. Shifts in resource allocation from somatic growth to reproduction are adaptive responses even in small-bodied cladocerans. 6. Predation cues do not seem to play a role in the induction of diapause in Moina nor for its termination in Moina and Diaphanosoma.