Date of Award

Spring 2019

Degree Name

Bachelor of Science

Major

Biology

First Advisor

Kent D. Dunlap

Second Advisor

Terri A. Williams

Third Advisor

Robert J. Fleming

Abstract

Social interactions can mitigate the damaging effects of threatening stimuli, a phenomenon termed ‘social buffering’. In two different forms of social buffering, social interactions reduce stress-induced decreases in brain cell proliferation and enhance recovery from somatic injury. However, the positive effects of social interactions on the brain cell proliferation response to somatic injury have not been extensively examined. Here, I investigated the social buffering of the brain cell proliferation response to tail injury in an electric fish, Apteronotus leptorhynchus. I ask three major questions: 1) Does social interaction mitigate the decrease in brain cell proliferation caused by simulated predatory tail injury?; 2) Does the timing of social interaction relative to injury alter this social buffering response?; and 3) Does tail injury modify affiliation with a non-injured social partner? I mimicked predatory injury through experimental tail amputation, exposed fish to paired interactions that varied in timing, duration, and recovery period, and measured cell proliferation (PCNA+ cell density) in the forebrain and midbrain. I also measured social affiliation based on the position of fish in retreat sites located near or distant to a stimulus fish. Social interaction either before or after tail amputation mitigated the negative effects of tail injury on brain cell proliferation. This buffering effect was specific to the forebrain and occurred after short-term (1 d) or long-term (7 d) recovery periods following tail amputation. However, social interaction both before (4 d) and after (7 d) tail amputation produced an even greater buffering effect in localized regions of the forebrain and midbrain. Similarly, fish exposed to social interaction both before and after tail amputation sought close affiliation with non-injured stimulus fish, but this effect did not occur in fish exposed to social interaction only after injury. Thus, despite the social buffering response on brain cell proliferation, it remains unclear whether fish modify their affiliation behavior in response to tail injury.

Comments

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

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