Adrian Perez

Date of Award


Degree Type



Biological Sciences

Director of Thesis

Jeff Dudycha

First Reader

Dan Speiser

Second Reader

Dan Speiser


The functionality of an eye is affected by a number of structural factors, and altering any of these factors often involves inevitable tradeoffs between resolution and sensitivity. However, it has been theoretically reasoned, and tested empirically, that increasing the size of an eye allows for both of these central features of vision to be improved due to corresponding increases in lens size. This study examines the relevance of this hypothesis for the vision of Daphnia in both interspecific and intraspecific contexts. The visual capabilities of six different species of Daphnia are tested using the optomotor response—a visually mediated behavior that our lab developed a scoring method for so that quantitative comparisons among species and individuals can be made. The main prediction we test is that increased ommatidia diameter will correlate with significant increase in optomotor behavior as an indirect measure of sensitivity and resolution, both across species and within populations. Our study offers evidence of significant optomotor responses in five species of Daphnia and demonstrates that there are significant differences in behavior among species. We provide evidence suggesting that ommatidia diameter is associated with increased visual capacity and performance between species; however, this correlation is not demonstrated within any of the six clonal populations. Consequently, we propose that there must be other visual traits, possibly associated with species identity and habitat differences, which may have influenced these results and warrant further investigation.

First Page


Last Page



© 2017, Adrian Perez

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