Life History Responses of Two Daphnia Species of Different Sizes against a Fish Kairomone.
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概要
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A reduction in size at maturity is of benefit to Daphnia populations in the presence of fish because it increases the probability for reproduction before being eaten by the fish, which prefer large prey. When exposed to a fish odor (kairomone), both the larger Daphnia galeata and the smaller D. ambigua changed their life history characteristics to reduce the mature size in their populations. However, their responses to the odor differed. D. galeata individuals did not reduce their mature size, but produced small offspring, which are expected to mature at a smaller size. On the other hand, D. ambigua individuals decreased their mature size, but did not reduce their offspring size. The different responses may be explained by the difference in vulnerability of the offspring to invertebrate predators, which prefer small zooplankton. Reducing off-spring size may increase their vulnerability to the predators. Offspring of D. ambigua are more vulnerable to these predators than those of D. galeata because of their small size. It is suggested that D. ambigua therefore responds to overall predator stress not by producing still smaller offspring, but by suppressing the individual growth rate in response to the fish odor in order to reduce the mature size.
- 日本陸水学会の論文
日本陸水学会 | 論文
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