Can you stomach it? Comparative transcriptomics and biochemistry of the stomachs of prickleback fishes (Stichaeidae) consuming different diets

Despite obvious whole animal, tissue level, and biochemical differences among species with different diets, dietary specialization has molecular underpinnings that are not well understood. In this project, we used comparative transcriptomics of stomach tissues to observe how prickleback fishes (Stichaeidae) achieve dietary-driven differences in stomach function. Xiphister mucosus (herbivore), X. atropurpureus (omnivore), Phytichthys chirus (omnivore) and the carnivorous Anoplarchus purpurescens were harvested from the wild, and fed omnivore and/or carnivore diets in the laboratory. Transcriptomes were sequenced for stomach tissues from two individuals per species and diet treatment. The number of shared orthologs varied with phylogenetic relatedness of the species (i.e., sister-taxa X. mucosus and X. atropurpureus shared the most expressed genes among the species), and differential expression and selection analyses are underway, although hydrogen-potassium ATPase appears to be under positive selection in some species. All four fish species strongly expressed pepsinogen and chitinase genes in their stomachs, yet biochemical activity levels (N ≥ 6 per species and diet treatment) of these two digestive enzymes matched natural diet, with the species consuming the most protein ( A. purpurescens) and chitin ( P. chirus) having the highest pepsin and chitinase activities, respectively. These activities were relatively unaltered by the laboratory diets, suggesting that activity level cannot be changed significantly through a dietary shift. Although intestinal carbohydrases typically show support for the Adaptive Modulation Hypothesis—a match among digestive enzyme activities with concentrations of ingested substrate—this may be one of the first investigations to observe such support for gastric enzymes. Thus, beyond being an important vertebrate innovation, the stomach may also provide digestive benefit depending on natural diet. NSF Grant IOS-1355224 and NSF DBI-1852096 This is the full abstract presented at the American Physiology Summit 2023 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.