Comparative studies of high performance swimming in sharks II. Metabolic biochemistry of locomotor and myocardial muscle in endothermic and ectothermic sharks

Abstract

SUMMARYMetabolic enzyme activities in red (RM) and white (WM) myotomal muscle and in the heart ventricle (HV) were compared in two lamnid sharks (shortfin mako and salmon shark), the common thresher shark and several other actively swimming shark species. The metabolic enzymes measured were citrate synthase(CS), an index of aerobic capacity, and lactate dehydrogenase (LDH), an index of anaerobic capacity. WM creatine phosphokinase (CPK) activity, an index of rapid ATP production during burst swimming, was also quantified. Enzyme activities in RM, WM and HV were similar in the two lamnid species. Interspecific comparisons of enzyme activities at a common reference temperature (20°C) show no significant differences in RM CS activity but higher CS activity in the WM and HV of the lamnid sharks compared with the other species. For the other enzymes, activities in lamnids overlapped with those of other shark species. Comparison of the HV spongy and compact myocardial layers in mako, salmon and thresher sharks reveals a significantly greater spongy CS activity in all three species but no differences in LDH activity. Adjustment of enzyme activities to in vivo RM and WM temperatures in the endothermic lamnids elevates CS and LDH in both tissues relative to the ectothermic sharks. Thus, through its enhancement of both RM and WM enzyme activity, endothermy may be an important determinant of energy supply for sustained and burst swimming in the lamnids. Although lamnid WM is differentially warmed as a result of RM endothermy, regional differences in WM CS and LDH activities and thermal sensitivities (Q10 values) were not found. The general pattern of the endothermic myotomal and ectothermic HV muscle metabolic enzyme activities in the endothermic lamnids relative to other active, ectothermic sharks parallels the general pattern demonstrated for the endothermic tunas relative to their ectothermic sister species. However, the activities of all enzymes measured are lower in lamnids than in tunas. Relative to lamnids, the presence of lower WM enzyme activities in the thresher shark (which is in the same order as the lamnids, has an RM morphology similar to that of the mako and salmon sharks and may be endothermic) suggests that other factors, such as behavior and swimming pattern, also affect shark myotomal organization and metabolic function.

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 relative values of red muscle mitochondrial density in the three shark species studied correspond with published red muscle citrate synthase activities: mean ± s.e.m. of 31.6±1.8·i.u.·g -1 tissue (N=30) for I. oxyrinchus; 22.3±6.3 (N=4) for P. glauca; 27.1±2.1 (N=7) for T. semifasciata (Dickson et al, 1993;Bernal et al, 2003b). This finding confirms that citrate synthase activity is an index of mitochondrial density in fish muscle.…”

Oxygen utilization and the branchial pressure gradient during ram ventilation of the shortfin mako,Isurus oxyrinchus: is lamnid shark–tuna convergence constrained by elasmobranch gill morphology?

“…Specifically, the interlamellar channel width in the mako is approximately twice that of tunas, N. C. Wegner and others resulting in one-half the lamellar frequency and one-half the gill surface area (Wegner et al, 2010b). This smaller respiratory area results in a lower volume of water that can be processed by the gills per unit time and this likely contributes to a reduced aerobic capacity in lamnids when compared with tunas, as manifested by lower aerobic enzyme activities, smaller amounts of red muscle and reduced sustainable swimming speeds (Bernal et al, 2003a;Bernal et al, 2003b;Sepulveda et al, 2007).…”

“…However, it is now well established that lamnid aerobic capacity is less than that of tunas. Lamnids have lower mitochondrial densities and aerobic enzyme activities (Bernal et al, 2003b), smaller gill surface areas (Muir, 1969;Emery and Szczepanski, 1986;Wegner et al, 2010a;Wegner et al, 2010b) and lower amounts of red muscle (Graham et al, 1983;Bernal et al, 2003a). Water-tunnel studies also indicate that the maximum sustainable swimming speed of the shortfin mako is much lower than that of tunas (Dewar and Graham, 1994;Blank et al, 2007;Sepulveda et al, 2007).…”

Licopeno no bem-estar de juvenis de tilápia do Nilo (Oreochromis niloticus): efeito sobre desempenho e parâmetros bioquímicos

“…O cortisol é um hormônio corticosteróide que aumenta após a exposição aguda ou crônica do peixe a um agente estressor, podendo desencadear atividade neoglicogênica e estímulo da mobilização de aminoácidos e de lipídios que serão utilizados como substratos energéticos, fato que afeta indiretamente o crescimento (LEACH e TAYLOR, 1982;DAVIS et al, 1985;SHERIDAN, 1986;VIJAYAN e LEATHERLAND, 1989;VIJAYAN et al, 1994 a,b (BERNAL et al, 2003;MCKENZIE et al, 2004;CLUTTERHAM et al, 2004;DALZIEL et al, 2005).…”

“…al.2005), ao cádmio (ALMEIDA, 2002), ao paraquat (FIGUEREIDO-FERNANDES et. al., 2006) e a outros pesticidas (BERNAL et al, 2003;MCKENZIE et al, 2004;CLUTTERHAM et al, 2004;DALZIEL et al, 2005 Não existem estudos relacionando a suplementação com licopeno e a supressão de hormônios em animais de criação intensiva. Porém, estudos com ratos mostraram os efeitos positivos da suplementação com antioxidantes, como o licopeno e β-caroteno, sobre a manutenção em níveis basais da concentração de cortisol após submeter os animais a um agente estressor (EL-DEMERDASH et.al., 2004;BESTAS et.…”