Vulnerability of cladoceran species to predation by the copepod Mesocyclops leuckarti: laboratory observations on the behavioural interactions between predator and prey

SUMMARY 1. We analysed the vulnerability of a number of cladoceran species (Bosmina longirostris, B. fatalis, Diaphanosoma brachyurum, Ceriodaphnia reticulata, Daphnia ambigua and D. pulex) to predation by Mesocyclops leuckarti in the laboratory. 2. The prey species represented a wide range of body size, morphology, and swimming behaviour. To compare vulnerability, we measured the efficiency of capture and ingestion of each prey species by Mesocyclops. We also measured the rate at which prey were damaged in attacks by Mesocyclops. 3. Mesocyclops preyed effectively on Diaphanosoma and small juvenile Ceriodaphnia but not on Bosmina or Daphnia. Observations suggested that various defence mechanisms, including protruding structures and swimming behaviour and speed, are important in determining prey vulnerability. 4. The body size of Daphnia and Ceriodaphnia seems to be important, because larger animals were better able to escape Mesocyclops attacks. Attacks by Mesocyclops often caused fatal damage, however, even to large Daphnia.