Predator-induced changes in morphology of a prey fish: the effects of food level and temporal frequency of predation risk |
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Authors: | Douglas P Chivers Xiaoxia Zhao Grant E Brown Tracy A Marchant Maud C O Ferrari |
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Institution: | (1) Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5E2;(2) Department of Biology, Concordia University, Montreal, QC, Canada, H4B 1R6 |
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Abstract: | In a series of experiments, we investigated the effects of food availability and risk frequency on the dynamics of predator-induced
changes in growth and morphology of prey fish using goldfish (Carassius auratus) as our test species. In experiment 1, we fed goldfish high or low food rations and exposed them to either alarm cues from
conspecifics, cues from swordtails or a water control. After 60 days, goldfish in the alarm cue treatment significantly increased
their body depth and body weight but had smaller body length than goldfish exposed to swordtails cues or water, likely reducing
their vulnerability to gape-limited predators. Importantly, food level had an impact on the amplitude of the morphological
changes. In experiment 2, goldfish were exposed to two different frequencies of predation cues or a water control for 50 days.
The cues were either continued or discontinued from day 51 to 100, and all cues were resumed from day 101 to 150. We found
that goldfish exposed to predation cues increased their depth and weight at a faster rate than did the goldfish exposed to
water, and of particular significance was the fact that frequency of risk had an effect on the amplitude of the change. When
the cues were interrupted, the increase in growth rate parameters was reduced to the level of the goldfish exposed to water.
However, when the cues were resumed, the rate increased to match the growth rate of the goldfish that were continuously exposed
to the cues. Finally, we staged encounters between goldfish of differing morphologies and yellow perch (Perca flavescens) and found that deep-bodied goldfish had better survival than the shallow-bodied ones. These experiments illustrate the dynamic
nature of inducible morphological defences. |
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Keywords: | Predator/prey interactions Morphological defences Inducible defences Chemical cues Goldfish |
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