caa a22 4500 605514534 CHVBK 20210128100705.0 cr unu---uuuuu 210128e20150201xx s 000 0 eng 10.1007/s00360-014-0879-z doi (NATIONALLICENCE)springer-10.1007/s00360-014-0879-z Gut transport characteristics in herbivorous and carnivorous serrasalmid fish from ion-poor Rio Negro water [Elektronische Daten] [Bernd Pelster, Chris Wood, Ben Speers-Roesch, William Driedzic, Vera Almeida-Val, Adalberto Val] Three closely related characids, Tambaqui (omnivore), black Piranha (carnivore), and Pacu (herbivore), all Serrasalmidae, inhabit the ion-poor, acidic Rio Negro. We compared O2-consumption and N excretion rates in vivo, and sodium, chloride, glucose, and ammonia transport characteristics of gut sac preparations in vitro. The Pacu had a significantly higher weight-specific oxygen consumption, and a lower N/Q ratio than the omnivorous Tambaqui, and a significantly lower urea-N excretion rate than the carnivorous black Piranha, suggesting N-limitation in the herbivorous Pacu. With a value of 2.62±0.15, gut to fork length ratio in the Pacu was about 2.5 times higher than in the black Piranha, and 2.0 times higher than in the Tambaqui. Anterior intestinal activities of three enzymes involved in N-fixation for amino acid synthesis (glutamate dehydrogenase, glutamate-oxaloacetate transferase, and glutamate-pyruvate transferase) were generally greatest in the carnivore and lowest in the herbivore species. In all three species, sodium, chloride, glucose, and ammonia were taken up at high rates from the intestine, resulting in an isosmotic fluid flux. Comparing the area-specific fluid flux of the anterior, mid, and posterior gut sections, no difference was detected between the three sections of the Pacu, while in the Tambaqui, it was highest in the anterior section, and in the black Piranha highest in the middle section. Overall, the area-specific uptake rates for sodium, chloride, glucose, and ammonia of anterior, mid, and posterior sections were similar in all three species, indicating that there is no difference in the area-specific transport rates associated with trophic position. The net ammonia uptake flux from gut interior was not significantly different from the net ammonia efflux to the serosal fluid, so that the ammonia removed from the intestine by the mucosal epithelium was quantitatively transferred through the tissue to the serosal side in all three species. Thus, metabolic activity of gut tissue did not significantly influence the net ammonia transfer. Due to the much higher gut to fork length ratio, the overall transport capacity of the gut of the herbivorous Pacu by far exceeded the transport capacity of their carnivorous and omnivorous relatives, thus compensating for the lower digestibility and the low Na+, Cl−, and N-content of the plant diet. Accordingly, in order to cope with the more difficult digestible plant material and the very low nitrogen content of plants, herbivorous fish have not evolved more effective area-specific transport capacities, but rather have increased the length of the gut. Springer-Verlag Berlin Heidelberg, 2014 Ion exchange nationallicence Gut function nationallicence Osmotic water flux nationallicence Ion regulation nationallicence Freshwater fish nationallicence Rio Negro nationallicence Pelster Bernd Institut für Zoologie, Leopold-Franzens-Universität Innsbruck, Technikerstr. 25, 6020, Innsbruck, Austria aut Wood Chris Department of Biology, McMaster University, L8S 4K1, Hamilton, ON, Canada aut Speers-Roesch Ben Department of Ocean Sciences, Memorial University of Newfoundland, A1C 5S7, St. John's, NL, Canada aut Driedzic William Department of Ocean Sciences, Memorial University of Newfoundland, A1C 5S7, St. John's, NL, Canada aut Almeida-Val Vera Instituto Nacional de Pesquisas da Amazonia, Manaus, Brazil aut Val Adalberto Instituto Nacional de Pesquisas da Amazonia, Manaus, Brazil aut Journal of Comparative Physiology B Springer Berlin Heidelberg 185/2(2015-02-01), 225-241 0174-1578 185:2<225 2015 185 360 https://doi.org/10.1007/s00360-014-0879-z text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s00360-014-0879-z text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Pelster Bernd Institut für Zoologie, Leopold-Franzens-Universität Innsbruck, Technikerstr. 25, 6020, Innsbruck, Austria aut NATIONALLICENCE 700 1- Wood Chris Department of Biology, McMaster University, L8S 4K1, Hamilton, ON, Canada aut NATIONALLICENCE 700 1- Speers-Roesch Ben Department of Ocean Sciences, Memorial University of Newfoundland, A1C 5S7, St. John's, NL, Canada aut NATIONALLICENCE 700 1- Driedzic William Department of Ocean Sciences, Memorial University of Newfoundland, A1C 5S7, St. John's, NL, Canada aut NATIONALLICENCE 700 1- Almeida-Val Vera Instituto Nacional de Pesquisas da Amazonia, Manaus, Brazil aut NATIONALLICENCE 700 1- Val Adalberto Instituto Nacional de Pesquisas da Amazonia, Manaus, Brazil aut NATIONALLICENCE 773 0- Journal of Comparative Physiology B Springer Berlin Heidelberg 185/2(2015-02-01), 225-241 0174-1578 185:2<225 2015 185 360