Assessing the Effects of Temperature, Feeding Status, and the Microbiome on the Maximal Activities of Several Enzymes Important to Energy Production and Ammonia Detoxification in the Intestines of Teleost Fish

This thesis examined the effects of temperature, feeding status, and the microbiome on the maximal activities of several enzymes important to energy production and ammonia (NH3) detoxification in the intestines of three species of teleosts: the goldfish, rainbow darter and central stoneroller. In warm-acclimated goldfish, intestinal and branchial tissues were more responsive to feeding, while renal tissues were not affected by digestion or thermal acclimation. This was reflected in the maximal enzyme activities of Na+, K+-ATPase (NKA), citrate synthase, pyruvate kinase, and glutamine synthetase (GS). Increased NKA activity following a meal suggested an increase in ATP demand, and amplified GS activity likely assists in enhanced NH3-detoxification processes in the intestinal tract. There was a strong effect of host species on intestinal tract bacteria composition and on enzyme activities in the rainbow darter and central stoneroller, and sampling location was a significant determinant of the central stoneroller intestinal microbiome.