Thermal Tolerance and Heat Hardening Ability Between Sexes in Gambusia affinis


Posing in front of my poster with Fred Nelson, my graduate student mentor, for the Educational Enrichment & Outreach Program Poster Symposium.

G. affinis larvae preserved in formalin.


Mosquitofish can adapt to extreme conditions including high water temperatures and acute temperature spikes and can alter the trophic levels in aquatic ecosystems. Unfortunately, given their capacity to tolerate warming, mosquitofish are equipped with the thermal tolerance to exacerbate their influence on freshwater ecosystems. Several studies conducted stress tolerance tests on mosquitofish to quantify fitness and predict responses to climate change, but few studies examined differences in stress tolerance between sexes, possibly overlooking an underlying factor in the fitness and ecological impact of each sex.


During my undergraduate career, I worked in  Dr. Anne Todgham's lab  to explore the physiological differences between the sexes of G. affinis with funding received from the Biology Undergraduate Scholars Program - Honors Research (BUSP-HR). I investigated differences in the male and female mosquitofish responses to acute temperature stress to reflect a future with frequent, intensified heat waves. I hypothesized that differences in energy allocation towards thermal stress tolerance in male and female mosquitofish would influence the upper thermal tolerance and capacity to acquire thermal tolerance. I found a trend where females possessed a higher upper thermal tolerance after exposure to a heat shock as well as a greater capacity to increase their thermal tolerance compared to males; however my results were not statistically significant. I communicated my findings via talks at the Western Society of Naturalist Conference (2020) and UC Davis Undergraduate Research Conference (2020) and a poster presentation at the UC Davis Educational Enrichment & Outreach Programs (EEOP) Annual Poster Symposium (2019).