Thermal independence of muscle tissue metabolism in the leatherback turtle, Dermochelys coriacea

Department of Bioscience and Biotechnology, Drexel University, Philadelphia, PA 19104, USA.
Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology (Impact Factor: 1.97). 08/1998; 120(3):399-403. DOI: 10.1016/S1095-6433(98)00024-5
Source: PubMed


Metabolic rates of animal tissues typically increase with increasing temperature and thermoregulatory control in an animal is a regional or whole body process. Here we report that metabolic rates of isolated leatherback turtle (Dermochelys coriacea) pectoralis muscle are independent of temperature from 5-38 degrees C (Q10 = 1). Conversely, metabolic rates of green turtle (Chelonia mydas) pectoralis muscle exhibit a typical vertebrate response and increase with increasing temperature (Q10 = 1.3-3.0). Leatherbacks traverse oceanic waters with dramatic temperature differences during their migrations from sub-polar to equatorial regions. The metabolic stability of leatherback muscle effectively uncouples resting muscle metabolism from thermal constraints typical of other vertebrate tissues. Unique muscle physiology of leatherbacks has important implications for understanding vertebrate muscle function, and is another strong argument for preservation of this endangered species.

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    • "This endothermy is thought to be achieved through their considerable body mass (gigantothermy; Paladino et al. 1990) and physiological adaptations including counter-current vasculature in the flippers (Greer et al. 1973), insulating subcutaneous lipid layers (Frair et al. 1972, Davenport et al. 1990) and variable lipid composition and distribution (Davenport et al. 1990). The independence of leatherback muscle metabolism to temperatures between 5 and 38°C (Penick et al. 1998) may also favour prolonged occupation of mid-latitude habitats. Leatherback turtles primarily feed on gelatinous organisms such as coelenterates (class Scyphozoa), including Aurelia, Chrysaora, Cyanea and Rhizostoma (Bleakney 1965, Brongersma 1972, Davenport 1998). "
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    ABSTRACT: Identifying key marine megavertebrate habitats has become ever more important as concern increases regarding global fisheries bycatch and accelerated climate change. This will be aided by a greater understanding of the patterns and processes determining the spatiotemporal distribution of species of conservation concern. We identify probable foraging grounds for leatherback turtles in the NE Atlantic using monthly landscapes of gelatinous organism distribution constructed from Continuous Plankton Recorder Survey data. Using sightings data (n = 2013 records, 1954 to 2003) from 9 countries (UK, Ireland, France, Belgium, The Netherlands, Denmark, Germany, Norway and Sweden), we show sea surface temperatures of approximately 10 to 12 degrees C most likely indicate the lower thermal threshold for accessible habitats during seasonal foraging migrations to high latitudes. Integrating maps of gelatinous plankton as a possible indicator of prey distribution with thermal tolerance parameters demonstrates the dynamic (spatial and temporal) nature of NE Atlantic foraging habitats. We highlight the importance of body size-related thermal constraints in structuring leatherback foraging populations and demonstrate a latitudinal gradient in body size (Bergmann's rule) where smaller animals are excluded from higher latitude foraging areas. We highlight the marine area of the European continental shelf edge as being both thermally accessible and prey rich, and therefore potentially supporting appreciable densities of foraging leatherbacks, with some suitable areas not yet extensively surveyed.
    Marine Ecology Progress Series 05/2007; 337:231-243. DOI:10.3354/meps337231 · 2.62 Impact Factor
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    • "The nonlinear temperature/coagulation profile for the green turtle samples was similar in form to that of the leatherback samples but was less dramatic. The difference in the magnitude of the responses observed in the leatherback and green turtle samples might be due to regional endothermy in green turtles (Standora et al., 1982), in contrast to the more complete complement of thermoregulatory adaptations in leatherbacks (Standora et al., 1984; Paladino et al., 1990; Penick et al., 1998). "
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    ABSTRACT: Functional hemostatic pathways are critical for the survival of all vertebrates and have been evolving for more than 400 million years. The overwhelming majority of studies of hemostasis in vertebrates have focused on mammals with very sparse attention paid to reptiles. There have been virtually no studies of the coagulation pathway in sea turtles whose ancestors date back to the Jurassic period. Sea turtles are often exposed to rapidly altered environmental conditions during diving periods. This may reduce their blood pH during prolonged hypoxic dives. This report demonstrates that five species of turtles possess only one branch of the mammalian coagulation pathway, the extrinsic pathway. Mixing studies of turtle plasmas with human factor-deficient plasmas indicate that the intrinsic pathway factors VIII and IX are present in turtle plasma. These two factors may play a significant role in supporting the extrinsic pathway by feedback loops. The intrinsic factors, XI and XII are not detected which would account for the inability of reagents to induce coagulation via the intrinsic pathway in vitro. The analysis of two turtle factors, factor II (prothrombin) and factor X, demonstrates that they are antigenically/functionally similar to the corresponding human factors. The turtle coagulation pathway responds differentially to both pH and temperature relative to each turtle species and relative to human samples. The coagulation time (prothrombin time) increases as the temperature decreases between 37 and 15 degrees C. The increased time follows a linear relationship, with similar slopes for loggerhead, Kemps ridley and hawksbill turtles as well as for human samples. Leatherback turtle samples show a dramatic nonlinear increased time below 23 degrees C, and green turtle sample responses were similar but less dramatic. All samples also showed increased prothrombin times as the pH decreased from 7.8 to 6.4, except for three turtle species. The prothrombin times decreased, to varying extents, in a linear fashion relative to reduced pH with the rate of change greatest in leatherbacks>green>loggerhead turtles. All studies were conducted with reagents developed for human samples which would impact on the quantitative results with the turtle samples, but are not likely to alter the qualitative results. These comparative studies of the coagulation pathway in sea turtles and humans could enhance our knowledge of structure/function relationships and evolution of coagulation factors.
    Comparative Biochemistry and Physiology Part B Biochemistry and Molecular Biology 09/2004; 138(4):399-406. DOI:10.1016/j.cbpc.2004.05.004 · 1.55 Impact Factor
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    ABSTRACT: Data on the location, date, sea temperature, and turtle size for 98 small (<145 cm) leatherback sea turtles Dermochelys coriacea demonstrate that leatherbacks less than 100 cm in carapace length occur only in waters warmer than 26degreesC.
    Marine Ecology Progress Series 04/2002; 230:289-293. DOI:10.3354/meps230289 · 2.62 Impact Factor
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