Date of Award

Spring 2020

Degree Name

Bachelor of Science



First Advisor

Kent D. Dunlap

Second Advisor

Daniel G. Blackburn

Third Advisor

Robert J. Fleming


Oxygen levels tend to remain at a steady state concentration in the Earth’s atmosphere, yet in some bodies of water, they can fluctuate and decrease drastically. Many organisms that inhabit the swamps, lakes, streams, and parts of the ocean where this occurs have evolved adaptations to manage this environmental uncertainty and continue normal oxygen consumption. The Lwamunda swamp in Uganda is chronically hypoxic, yet it is home to many species, including the electric fish Petrocephalus degeni. P. degeni are unusual by nature of their immense brain, and the Lwamunda swamp appears ill-suited for maintaining this large, metabolically active organ. To determine the possible mechanisms P. degeni employ for survival and brain maintenance in this hypoxic swamp, 33 individuals were collected aiming to analyze their brain cell proliferation. One-third were immediately sacrificed, and two-thirds were transported to a laboratory and divided into hypoxic and normoxic environments for two weeks. All brains were collected, and new brain cell proliferation was quantified using PCNA immunohistochemistry. P. degeni from the hypoxic lab condition showed significantly fewer PCNA+ cells than their conspecifics in normoxic water, and individuals harvested directly from the field showed the overall highest density of PCNA+ brain cells. Our results suggest that hypoxia and captivity negatively impacted brain cell growth in P. degeni. The activation of hypoxia-inducible factors (HIFs) likely mediated this reduction in brain cell proliferation and the corresponding oxygen demand. Despite showing a reduction in new brain cell growth, P. degeni remains capable of surviving and maintaining their large brain in extremely hypoxic conditions.


Senior thesis completed at Trinity College, Hartford, CT for the degree of Bachelor of Science in Biology.