Phenotypic plasticity of eye size in the freshwater zooplankton Daphnia in response to predatory cues

Williams, Brandon
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Florida Southern College
The eye is a complex organ which plays a crucial role in how an animal perceives and responds to its environment. Recent evidence has suggested that visual predation in an animal’s environment can influence the eye size morphology. Despite mounting evidence suggesting other factors that may be involved in evolution of eyes the literature is heavily dominated by articles solely looking at the effects of environmental light levels. Therefore, this study aimed to add to the literature regarding predation and eye size by looking at how varying degrees of predation affect eye morphology in a population of a small freshwater crustacean, Daphnia. Here, I test the visual target hypothesis the hypothesis predicts that the eye size of a Daphnia population under heavy predation will be significantly smaller than the populations exposed to little or no predation. In order to test this hypothesis, four species of Daphnia were split into two groups which were raised in water containing mosquitofish kairomones or filtered lake water. The groups were raised for two weeks and then body and eye size measurements were taken and showed that absolute body size and eye size were affected by the fish, but not relative eye size.
Honors Thesis Spring 2020
Daphniidae, Eye -- Anatomy, Eye -- Examination, Eye tracking, Predation (Biology)