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How fishes thrive on different diets is not understood as well as for terrestrial animals. Thus, examining the flexibility of gut function in fishes with different diets provides insight into dietary specialization in the largest vertebrate class. In this study, we measured the amylolytic activities in the guts of closely related, sympatric species: Xiphister mucosus (herbivore), X. atropurpureus (omnivore), Phytichthys chirus (omnivore), and Anoplacharus purpurescens (carnivore). For all species, the amylase activity decreased moving distally along the intestine, but less so for the carnivorous A. purpurescens. Overall, our results—more elevated amylase activity in those fish eating more algae—agree with the Adaptive Modulation Hypothesis (AMH), which suggests that there should be a match between enzymatic activity and dietary substrate intake. Measurements of proteases and lipases are in progress, but we anticipate some support for AMH in other enzyme classes. Moreover, we are also measuring these same enzyme activities in these same species fed omnivorous or carnivorous diets in the laboratory. The flexibility of the intestines of the fish species to accommodate different food types provides insight into their roles in the ecosystems and how fixed the vertebrate digestive system can be. NSF IOS 1355224 Undergraduate Research Opportunity Program at University of California, Irvine. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Steinmann et al. (Wed,) studied this question.