caa a22 4500 60623019X CHVBK 20210128101212.0 cr unu---uuuuu 210128e20150801xx s 000 0 eng 10.1007/s10695-015-0055-8 doi (NATIONALLICENCE)springer-10.1007/s10695-015-0055-8 Digestive enzyme activities are higher in the shortfin mako shark, Isurus oxyrinchus , than in ectothermic sharks as a result of visceral endothermy [Elektronische Daten] [Kyle Newton, James Wraith, Kathryn Dickson] Lamnid sharks are regionally endothermic fishes that maintain visceral temperatures elevated above the ambient water temperature. Visceral endothermy is thought to increase rates of digestion and food processing and allow thermal niche expansion. We tested the hypothesis that, at in vivo temperatures, the endothermic shortfin mako shark, Isurus oxyrinchus, has higher specific activities of three digestive enzymes—gastric pepsinand pancreatic trypsin and lipase—than the thresher shark, Alopias vulpinus, and the blue shark, Prionace glauca, neither of which can maintain elevated visceral temperatures. Homogenized stomach or pancreas tissue obtained from sharks collected by pelagiclongline was incubated at both 15 and 25°C, at saturating substrate concentrations, to quantify tissue enzymatic activity. The mako had significantly higher enzyme activities at 25°C than did the thresher and blue sharks at 15°C. This difference was not a simple temperature effect, because at 25°C the mako had higher trypsin activity than the blue shark and higher activities for all enzymes than the thresher shark. We also hypothesized that the thermal coefficient, or Q 10 value, would be higher for the mako shark than for the thresher and blue sharks because of its more stable visceral temperature. However, the mako and thresher sharks had similar Q 10 values for all enzymes, perhaps because of their closer phylogenetic relationship. The higher in vivo digestive enzyme activities in the mako shark should result in higher rates of food processing and may represent a selective advantage of regional visceral endothermy. Springer Science+Business Media Dordrecht, 2015 Digestive enzyme nationallicence Lamnid shark nationallicence Lipase nationallicence Pepsin nationallicence Trypsin nationallicence Temperature nationallicence Visceral endothermy nationallicence A xxx : Absorbance at a specific wavelength of XXXnm nationallicence ANOVA : Analysis of variance nationallicence ε : Extinction coefficient nationallicence FL : Fork length nationallicence Q 10 : Temperature coefficient=(enzyme activity25°C/enzyme activity15°C) nationallicence U : Unit of enzyme activity=μmol of substrate converted to product min−1 nationallicence s.e.m. : Standard error of the mean nationallicence Newton Kyle Department of Biological Science, California State University Fullerton, 800N. State College Blvd, 92834, Fullerton, CA, USA aut Wraith James Fisheries Resource Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 8901 La Jolla Shores Drive, 92037, La Jolla, CA, USA aut Dickson Kathryn Department of Biological Science, California State University Fullerton, 800N. State College Blvd, 92834, Fullerton, CA, USA aut Fish Physiology and Biochemistry Springer Netherlands 41/4(2015-08-01), 887-898 0920-1742 41:4<887 2015 41 10695 https://doi.org/10.1007/s10695-015-0055-8 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/s10695-015-0055-8 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Newton Kyle Department of Biological Science, California State University Fullerton, 800N. State College Blvd, 92834, Fullerton, CA, USA aut NATIONALLICENCE 700 1- Wraith James Fisheries Resource Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 8901 La Jolla Shores Drive, 92037, La Jolla, CA, USA aut NATIONALLICENCE 700 1- Dickson Kathryn Department of Biological Science, California State University Fullerton, 800N. State College Blvd, 92834, Fullerton, CA, USA aut NATIONALLICENCE 773 0- Fish Physiology and Biochemistry Springer Netherlands 41/4(2015-08-01), 887-898 0920-1742 41:4<887 2015 41 10695