Experimental Tests on Sperm and Seasonal Morphology Change in the Endangered Redside Dace (Clinostomus elongatus)

Freshwater fishes are in rapid decline and are one of the most at-risk vertebrate groups. Redside Dace (Clinsotomus elongatus) are in severe decline across much of their range, yet pockets of high abundance still exist; this, along with other factors, makes them an excellent species to study conservation biology questions. The comprehensive objective of this thesis was to test hypotheses that can contribute to two broad areas of research on sperm movement and organ morphology while also providing potentially useful information for Redside Dace conservation. Specifically, whether a temperature surge event affects Redside Dace sperm and how seasonal organ change indicates when Redside Dace are potentially susceptible to population decline. First, we experimentally tested whether an acute temperature surge event would negatively impact Redside Dace sperm movement. We found no evidence that either increased acclimation or activation temperature affected Redside Dace sperm movement. Second, we examined seasonal morphology changes in adult males, adult females, and juveniles as well as differences between these groups. We found significant seasonal changes to gonads, livers, guts, hearts, body condition, and red spot area in Redside Dace; as well as age and sex based morphological differences. Collectively, these results provide valuable information about sperm movement and seasonal organ change that is potentially useful in Redside Dace conservation and also contributes to two areas of ecology/physiology research