Title

The Developmental and Genetic Basis of Differences in Cave and Surface-dwelling Forms of the Crustacean, Asellus aquaticus

Graduation Date

5-2017

Document Type

Master's Thesis

Degree Name

Master of Science

Department or Program

Biological Sciences

Department or Program Chair

Maggie Louie, Ph.D.

First Reader

Meredith Protas, Ph.D.

Second Reader

Emily Willingham, Ph.D.

Abstract

Currently, there are many gaps in our understanding of the genetic mechanisms responsible for human diseases. One novel method to bridge these gaps is to investigate the naturally occurring variation of wild populations, which is arguably more similar to the genetic complexity present in human disease than artificially induced mutations in model species. Species adapted to subterranean environments often share phenotypic characteristics such as the reduction or complete absence of eyes, reduced pigmentation, and enhanced sensory systems. In order to understand the evolution of these morphological changes, we selected an invertebrate model system the freshwater isopod crustacean Asellus aquaticus, which contains both surface-dwelling and blind cave-dwelling forms. Our goal was to investigate how and when during embryonic development all of these morphologically differences came about. In addition, we wanted to investigate the molecular mechanisms of eye degeneration and to develop methods to identify differential expression between cave and surface forms in the candidate genes hedgehog, sine oculis, pax2, pygopus, and retinal dehydrogenase 11. The results from this work have helped address evolutionary questions that have been historically difficult to dissect and have generated a much-needed animal model system to better understand when and how cave characteristics develop.

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