The prevalence of diapause response to risk of size-selective predation in small- and large-bodied prey species |
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Authors: | M Slusarczyk A Ochocka D Cichocka |
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Institution: | (1) Department of Hydrobiology, University of Warsaw, Banacha 2, 02-097 Warszawa, Poland;(2) Institute of Environmental Protection-National Research Institute, ul. Krucza 5/11d, 00-548 Warszawa, Poland |
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Abstract: | The prevalence of diapause response to the simulated threat of fish predation was compared in three species of planktonic
crustaceans of the genus Daphnia (D. magna, D. pulicaria and D. longispina), which due to their different body size vary in vulnerability to fish predation pressure in natural conditions. Higher incidence
of diapause response was presumed in the larger-bodied species, which due to their higher conspicuousness and higher energetic
content experience the greatest size-selective pressure from visually foraging fish. Small-bodied species were expected to
utilize less costly yet less effective active defences, e.g. lower conspicuousness achieved due to slower body growth when
facing risk of size-selective predation. Proportions of females forming diapausing structures as well as females body size
at the maturation period were compared in experimental beakers containing or not containing fish kairomones (chemical cues
of fish predation) in a few clonal lineages of 3 species of Daphnia derived from a single lake inhabited by fish. The highest incidence of diapause response to fish kairomones was observed
in D. magna (when measured both as proportion of sensitive individuals and as proportion of inductive clones), the largest of the tested
Daphnia species. The lowest proportion of individuals and clones that employed diapause was reported in the smallest tested species,
D. longispina. In addition, the large-bodied Daphnia (D. magna) showed a greater reduction in body size in response to fish kairomones than the small-bodied species (D. longispina). The results of the present study support the assumption of higher prevalence of diapause response to the threat of selective
predation in larger and more vulnerable prey species. |
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