Meeting Abstract

98.3  Sunday, Jan. 6  Digestive enzyme activities elucidate the digestive strategies of prickleback fishes (family Stichaeidae) with different diets GERMAN, DP; Univ. of California, Irvine dgerman@uci.edu

The patterns of digestive enzyme activities along the digestive tract of an animal can reveal the strategy that an animal takes to acquire resources from their food. In this study I examined how the activity levels of carbohydrases, proteases, and lipase change along the guts of five closely related prickleback fish species with different diets: Cebidichthys violaceus (herbivore), Xiphister mucosus (herbivore), X. atropurpureus (omnivore), Phytichthys chirus (omnivore), and Anoplarchus purpurescens (carnivore). Digestive enzyme activities were measured in the pyloric caeca (which include pancreatic tissue in pricklebacks), and in the proximal, mid, and distal intestines of the fishes. All five species showed decreasing amylase activity moving distally along the intestine, whereas disaccharidase activities tended to peak in the mid intestines of the herbivores and omnivores, and decrease moving distally along the intestine of the carnivorous A. purpurescens. Collectively, these observations, in concert with moderate concentrations of short chain fatty acids in the fishes’ guts, are consistent with the “plug-flow reactor” model of digestion, and suggest a reliance on endogenous digestive processes as opposed to microbial endosymbionts. Enzyme activity patterns (including proteolytic and lipolytic activities, which are in progress) will be discussed in the context of the fishes’ feeding ecology and evolutionary history.