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Kathryn A Dickson - One of the best experts on this subject based on the ideXlab platform.
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Digestive enzyme activities are higher in the shortfin mako Shark, Isurus oxyrinchus, than in ectothermic Sharks as a result of visceral endothermy
Fish Physiology and Biochemistry, 2015Co-Authors: Kyle C. Newton, James Wraith, Kathryn A DicksonAbstract: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 pepsin and 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 pelagic longline 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.
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mitochondrial proton leak rates in the slow oxidative myotomal muscle and liver of the endothermic shortfin mako Shark isurus oxyrinchus and the ectothermic Blue Shark prionace glauca and leopard Shark triakis semifasciata
The Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark ( Isurus oxyrinchus ), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark ( Prionace glauca ) and leopard Shark ( Triakis semifasciata ). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20°C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP+). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H+ min-1 mg-1 protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
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Mitochondrial proton leak rates in the slow, oxidative myotomal muscle and liver of the endothermic shortfin mako Shark (Isurus oxyrinchus) and the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata).
Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark (Isurus oxyrinchus), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20 degrees C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP(+)). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H(+) min(-1) mg(-1) protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
Cindy A Duong - One of the best experts on this subject based on the ideXlab platform.
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mitochondrial proton leak rates in the slow oxidative myotomal muscle and liver of the endothermic shortfin mako Shark isurus oxyrinchus and the ectothermic Blue Shark prionace glauca and leopard Shark triakis semifasciata
The Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark ( Isurus oxyrinchus ), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark ( Prionace glauca ) and leopard Shark ( Triakis semifasciata ). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20°C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP+). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H+ min-1 mg-1 protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
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Mitochondrial proton leak rates in the slow, oxidative myotomal muscle and liver of the endothermic shortfin mako Shark (Isurus oxyrinchus) and the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata).
Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark (Isurus oxyrinchus), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20 degrees C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP(+)). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H(+) min(-1) mg(-1) protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
Chugey A Sepulveda - One of the best experts on this subject based on the ideXlab platform.
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Functional morphology of the gills of the shortfin mako, Isurus oxyrinchus, a lamnid Shark.
Journal of morphology, 2010Co-Authors: Nicholas C. Wegner, Chugey A Sepulveda, Kenneth R. Olson, Kelly A. Hyndman, Jeffrey B. GrahamAbstract:This study examines the functional gill morphology of the shortfin mako, Isurus oxyrinchus ,t o determine the extent to which its gill structure is conver- gent with that of tunas for specializations required to increase gas exchange and withstand the forceful branchial flow induced by ram ventilation. Mako gill structure is also compared to that of the Blue Shark, Prio- nace glauca, an epipelagic species with lower metabolic requirements and a reduced dependence on fast, continu- ous swimming to ventilate the gills. The gill surface area of the mako is about one-half that of a comparably sized tuna, but more than twice that of the Blue Shark and other nonlamnid Shark species. Mako gills are also distin- guished from those of other Sharks by shorter diffusion distances and a more fully developed diagonal blood-flow pattern through the gill lamellae, which is similar to that found in tunas. Although the mako lacks the filament and lamellar fusions of tunas and other ram-ventilating tele- osts, its gill filaments are stiffened by the elasmobranch interbranchial septum, and the lamellae appear to be sta- bilized by one to two vascular sacs that protrude from the lamellar surface and abut sacs of adjacent lamellae. Vaso- active agents and changes in vascular pressure poten- tially influence sac size, consequently effecting lamellar rigidity and both the volume and speed of water through the interlamellar channels. However, vascular sacs also occur in the Blue Shark, and no other structural elements of the mako gill appear specialized for ram ventilation. Rather, the basic elasmobranch gill design and pattern of branchial circulation are both conserved. Despite special- izations that increase mako gill area and efficacy relative to other Sharks, the basic features of the elasmobranch gill design appear to have limited selection for a larger gill surface area, and this may ultimately constrain mako aerobic performance in comparison to tunas. J. Morphol. 000:000-000, 2010. 2010 Wiley-Liss, Inc.
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mitochondrial proton leak rates in the slow oxidative myotomal muscle and liver of the endothermic shortfin mako Shark isurus oxyrinchus and the ectothermic Blue Shark prionace glauca and leopard Shark triakis semifasciata
The Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark ( Isurus oxyrinchus ), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark ( Prionace glauca ) and leopard Shark ( Triakis semifasciata ). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20°C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP+). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H+ min-1 mg-1 protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
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Mitochondrial proton leak rates in the slow, oxidative myotomal muscle and liver of the endothermic shortfin mako Shark (Isurus oxyrinchus) and the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata).
Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark (Isurus oxyrinchus), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20 degrees C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP(+)). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H(+) min(-1) mg(-1) protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
Jeffrey B. Graham - One of the best experts on this subject based on the ideXlab platform.
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Functional morphology of the gills of the shortfin mako, Isurus oxyrinchus, a lamnid Shark.
Journal of morphology, 2010Co-Authors: Nicholas C. Wegner, Chugey A Sepulveda, Kenneth R. Olson, Kelly A. Hyndman, Jeffrey B. GrahamAbstract:This study examines the functional gill morphology of the shortfin mako, Isurus oxyrinchus ,t o determine the extent to which its gill structure is conver- gent with that of tunas for specializations required to increase gas exchange and withstand the forceful branchial flow induced by ram ventilation. Mako gill structure is also compared to that of the Blue Shark, Prio- nace glauca, an epipelagic species with lower metabolic requirements and a reduced dependence on fast, continu- ous swimming to ventilate the gills. The gill surface area of the mako is about one-half that of a comparably sized tuna, but more than twice that of the Blue Shark and other nonlamnid Shark species. Mako gills are also distin- guished from those of other Sharks by shorter diffusion distances and a more fully developed diagonal blood-flow pattern through the gill lamellae, which is similar to that found in tunas. Although the mako lacks the filament and lamellar fusions of tunas and other ram-ventilating tele- osts, its gill filaments are stiffened by the elasmobranch interbranchial septum, and the lamellae appear to be sta- bilized by one to two vascular sacs that protrude from the lamellar surface and abut sacs of adjacent lamellae. Vaso- active agents and changes in vascular pressure poten- tially influence sac size, consequently effecting lamellar rigidity and both the volume and speed of water through the interlamellar channels. However, vascular sacs also occur in the Blue Shark, and no other structural elements of the mako gill appear specialized for ram ventilation. Rather, the basic elasmobranch gill design and pattern of branchial circulation are both conserved. Despite special- izations that increase mako gill area and efficacy relative to other Sharks, the basic features of the elasmobranch gill design appear to have limited selection for a larger gill surface area, and this may ultimately constrain mako aerobic performance in comparison to tunas. J. Morphol. 000:000-000, 2010. 2010 Wiley-Liss, Inc.
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mitochondrial proton leak rates in the slow oxidative myotomal muscle and liver of the endothermic shortfin mako Shark isurus oxyrinchus and the ectothermic Blue Shark prionace glauca and leopard Shark triakis semifasciata
The Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark ( Isurus oxyrinchus ), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark ( Prionace glauca ) and leopard Shark ( Triakis semifasciata ). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20°C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP+). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H+ min-1 mg-1 protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
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Mitochondrial proton leak rates in the slow, oxidative myotomal muscle and liver of the endothermic shortfin mako Shark (Isurus oxyrinchus) and the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata).
Journal of Experimental Biology, 2006Co-Authors: Cindy A Duong, Jeffrey B. Graham, Chugey A Sepulveda, Kathryn A DicksonAbstract:Mitochondrial proton leak was assessed as a potential heat source in the slow, oxidative (red) locomotor muscle and liver of the shortfin mako Shark (Isurus oxyrinchus), a regional endotherm that maintains the temperature of both tissues elevated above ambient seawater temperature. We hypothesized that basal proton leak rates in red muscle and liver mitochondria of the endothermic shortfin mako Shark would be greater than those of the ectothermic Blue Shark (Prionace glauca) and leopard Shark (Triakis semifasciata). Respiration rate and membrane potential in isolated mitochondria were measured simultaneously at 20 degrees C using a Clark-type oxygen electrode and a lipophilic probe (triphenylmethylphosphonium, TPMP(+)). Succinate-stimulated respiration was titrated with inhibitors of the electron transport chain, and the non-linear relationship between respiration rate and membrane potential was quantified. Mitochondrial densities of both tissues were measured by applying the point-contact method to electron micrographs so that proton leak activity of the entire tissue could be assessed. In all three Shark species, proton leak occurred at a higher rate in red muscle mitochondria than in liver mitochondria. For each tissue, the proton leak curves of the three species overlapped and, at a membrane potential of 160 mV, mitochondrial proton leak rate (nmol H(+) min(-1) mg(-1) protein) did not differ significantly between the endothermic and ectothermic Sharks. This finding indicates that red muscle and liver mitochondria of the shortfin mako Shark are not specialized for thermogenesis by having a higher proton conductance. However, mako mitochondria did have higher succinate-stimulated respiration rates and membrane potentials than those of the two ectothermic Sharks. This means that under in vivo conditions mitochondrial proton leak rates may be higher in the mako than in the ectothermic species, due to greater electron transport activity and a larger proton gradient driving proton leak. We also estimated each tissue's total proton leak by combining mitochondrial proton leak rates at 160 mV and tissue mitochondrial density data with published values of relative liver or red muscle mass for each of the three species. In red muscle, total proton leak was not elevated in the mako Shark relative to the two ectothermic species. In the liver, total proton leak would be higher in the mako Shark than in both ectothermic species, due to a lower proton conductance in the Blue Shark and a lower liver mitochondrial content in the leopard Shark, and thus may contribute to endothermy.
Hiroaki Matsunaga - One of the best experts on this subject based on the ideXlab platform.
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distribution body length and abundance of Blue Shark and shortfin mako offshore of northeastern japan as determined from observed pelagic longline data 2000 2014
Fisheries Oceanography, 2016Co-Authors: Seiji Ohshimo, Hiroaki Matsunaga, Yuki Fujinami, Ko Shiozaki, Mikihiko Kai, Yasuko Semba, Nobuhiro Katsumata, Daisuke Ochi, Hiroshi Minami, Masashi KiyotaAbstract:Longline surveys have been conducted in the Northwest Pacific Ocean from 2000 to 2014 using chartered commercial longline vessels. Each year, two cruises were conducted offshore of northeastern Japan from mid-April to mid-June. For each longline set during the surveys, onboard scientists collected detailed biological information about the species caught, such as the size and sex, and recorded the catch numbers for all species. Blue Shark (Prionace glauca) and shortfin mako (Isurus oxyrinchus) have eurythermal distributions, but the application of a generalized additive model (GAM) showed that the sea surface temperatures (SSTs) at catch sites positive for shortfin mako were warmer than those for Blue Shark. On the basis of the GAM, the probabilities of occurrence of both Sharks differed by size category: small Sharks had a narrower SST range than that of large Sharks. Most catches of both Sharks were juveniles, and the nominal catch rate of Blue Shark was more than 10 times that of shortfin mako. The standardized catch per unit effort (CPUE) for both species was calculated using a generalized linear model (GLM) with negative binomial errors, or a delta-lognormal GLM. The standardized CPUE for Blue Shark in the second quarter of the year peaked in the mid-2000s and then decreased, but it has been increasing since 2012. The CPUE for shortfin mako in the second quarter generally increased, with fluctuations.
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SUMMARY
2015Co-Authors: Hiroaki MatsunagaAbstract:In Japan s ́ Atlantic observer program 499 Sharks of six species were released with tags by scientific observers from 2000 until now. Blue Shark was dominant occupying more than 93% followed by porbeagle (3%). Twenty-seven (27) tags attached to Blue Sharks were returned and ratio of recapture was 5.4 %. The longest time at liberty is 610 days and the longest migration is about 3200 km, which suggest the large-scale migration of Blue Shark. RÉSUMÉ De 2000 à nos jours, des observateurs scientifiques ont remis à l’eau 499 requins de six espèces auxquels des marques avaient été apposées dans le cadre du programme japonais d’observateurs mené dans l’Atlantique. Le requin peau bleue était l’espèce dominante, représentant plus de 93 % des espèces marquées, suivi du requin-taupe commun (3%). Vingt-sept (27) marques apposées à des requins peaux bleues ont été renvoyées et le taux de récupération s’élevait à 5,4%. La plus longue période de temps passé en liberté était de 610 jours et la plus longue migration était d’environ 3.200 km, données qui indiquent la migration à grande échelle du requin peau bleue. RESUMEN Desde 2000 hasta ahora, en el programa de observadores japonés en el Atlántico se han liberado 499 tiburones de seis especies con marcas colocadas por los observadores científicos. La tintorera era la especie dominante con más del 93%, seguida por el marrajo sardinero (3%). Veintisiete (27) marcas colocadas en las tintoreras fueron recuperadas y la ratio de recaptura fue del 5,4%. El mayor tiempo en libertad es de 610 días y la mayor migración es de aproximadamente 3.200 km, lo que sugiere una migración a gran escala de la tintorera
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CPUE TREND FOR PORBEAGLE CAUGHT BY JAPANESE TUNA LONGLINE IN THE SBT FISHERY GROUND DURING 1992-2007
2010Co-Authors: Hiroaki MatsunagaAbstract:SUMMARY Porbeagle is one of the main pelagic Shark species, following Blue Shark, caught by the southern Bluefin tuna (SBT) fishery of Japan. The standardized CPUE for porbeagle was calculated using the SBT observer data from 1992 to 2007. Some fluctuations are observed but no clear trend of standardized CPUE is observed for this species. This result is supposed to indicate that the stock status of porbeagle did not change significantly during the research period in this fishery ground.
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standardized cpue for Blue Shark and shortfin mako caught by the japanese tuna longline fishery in the atlantic ocean
2008Co-Authors: Hiroaki MatsunagaAbstract:SUMMARY The standardized CPUEs for Blue Shark and shortfin mako caught by the Japanese tuna longline fishery in the Atlantic Ocean were updated using filtered logbook data during 1971-2006 for Blue Shark and 1994-2006 for shortfin mako whose reporting rates were more than 80%. Blue Shark CPUE shows some fluctuations and relatively stable trends during the past three decades for North, South and whole Atlantic stock hypotheses. Shortfin mako CPUE indicates decreasing trend until 2001 but after then recovery to the level at beginning is observed.
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estimation of catches for Blue Shark and shortfin mako by the japanese tuna longline fishery in the atlantic ocean 1994 2005
2008Co-Authors: Hiroaki MatsunagaAbstract:SUMMARY Catches for Blue Shark and shortfin mako caught by the Japanese tuna longline fishery in the Atlantic Ocean were estimated using species-specific logbook data from 1994 to 2005 filtered with a 70% reporting rate. Yearly catches of Blue Shark in the entire region were estimated to be 105,000-335,000 (mean 199,000) in number and 2,800-9,900 metric tons (mean 5,600) in weight. Catches of shortfin mako were estimated to be 3,000-38,800 (mean 14,700) and 120-1,790 tons (mean 640). Decreasing trends were observed in both catch number and in weight of the two species. However, the catches of shortfin mako in 1994 and 1995 are supposed to be over-estimated because some catches of Blue Shark in 1994 and 1995 are considered to be recorded as those of shortfin mako by mistake. Therefore, it is not appropriate to use these catch estimations at present. RESUME