Do herbivorous minnows have “plug-flow reactor” guts? Evidence from digestive enzyme activities,gastrointestinal fermentation,and luminal nutrient concentrations |
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Authors: | Donovan P German |
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Institution: | (1) Department of Zoology, University of Florida, Gainesville, FL, USA;(2) Present address: Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA |
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Abstract: | Few investigations have empirically analyzed fish gut function in the context of chemical reactor models. In this study, digestive
enzyme activities, levels of gastrointestinal fermentation products short chain fatty acids (SCFA)], luminal nutrient concentrations,
and the mass of gut contents were measured along the digestive tract in herbivorous and carnivorous minnows to ascertain whether
their guts function as “plug-flow reactors” (PFRs). Four of the species, Campostoma anomalum, C. ornatum, C. oligolepis, and C. pauciradii, are members of a monophyletic herbivorous clade, whereas the fifth species, Nocomis micropogon, is a carnivore from an adjacent carnivorous clade. In the context of a PFR model, the activities of amylase, trypsin and
lipase, and the concentrations of glucose, protein, and lipid were predicted to decrease moving from the proximal to the distal
intestine. I found support for this as these enzyme activities and nutrient concentrations generally decreased moving distally
along the intestine of the four Campostoma species. Furthermore, gut content mass and the low SCFA concentrations did not change (increase or decrease) along the gut
of any species. Combined with a previous investigation suggesting that species of Campostoma have rapid gut throughput rates, the data presented here generally support Campostoma as having guts that function as PFRs. The carnivorous N. micropogon showed some differences in the measured parameters, which were interpreted in the contexts of intake and retention time to
suggest that PFR function breaks down in this carnivorous species. |
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Keywords: | Digestion Digestive physiology Nutritional ecology Chemical reactor models Microbial |
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