Document Type


Date of Award


Degree Name

Master of Science in Biology - (M.S.)


Federated Department of Biological Sciences

First Advisor

Eric Scott Fortune

Second Advisor

Daphne F. Soares

Third Advisor

Xiaonan Tai


Organisms commonly modulate their behavioral activity in relation to the 24-hour solar cycle. This modulation of behavior is driven by a combination of responses to external cues in the environment, such as light/dark visual signals, and internal pattern generators that can persist in the absence of external cues. However, there are animals that live in caves or in the deep sea that are isolated from solar circadian cues. How these animals regulate their behavioral activity in relation to external and internal rhythms is an open question in neuroscience that may help us to understand the mechanisms that other animals, including humans, use to regulate behavioral states including sleep. This thesis explores functional relations between external and internal mechanisms for the regulation of activity patterns in two groups of Astyanax mexicanus, cavefish and surface fish. We found that surface fish had profound circadian modulation of behavior that was absent in cavefish.



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