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: 2.17). 08/1998; 120(3):399-403. DOI: 10.1016/S1095-6433(98)00024-5
Source: PubMed

ABSTRACT 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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    ABSTRACT: Leatherback sea turtles (Dermochelys coriacea) can maintain body temperature (T(B)) up to 18 degrees C above that of the surrounding sea water (T(W)) which allows leatherbacks to enter cold temperate waters and have the largest global range of any reptile. Using a cylindrical model of a leatherback we investigated the extent to which heat production through variation of swim speed could be used in a leatherback's thermal strategy. Drag force of a full scale cast of a leatherback was measured in a low velocity wind tunnel to obtain an estimate of the metabolic cost needed to offset drag. Heat released in the core of a turtle as a byproduct of the metabolic cost of locomotion is conducted from the core of the turtle to the surrounding water through its insulation layer. By keeping insulation thickness constant, we highlight the effectiveness of swim speed in maintaining T(B)-T(W). Our model, when tested against published data at a given T(W), showed a close correlation between predicted and measured swimming speed at a given T(B). We conclude that the ability to maintain a large T(B)-T(W) is an interplay between mass, insulation thickness and water temperature selection but behavioural control of swimming speed predominates.
    Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 07/2007; 147(2):323-31. · 2.17 Impact Factor
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    ABSTRACT: Quantification of metabolic rates (MR) is fundamental to understanding an individual organism's physiology and life history, as well as overall population dynamics. Applications of MR measurements have increased both in quantity and quality across animal ecology over the past 50 years. Included in this trend, research on MRs of marine turtles and its consequences for these unique ectothermic vertebrates has matured significantly. We reviewed existing literature on marine turtle MRs in the context of the physiology, ecology, and life history of these animals. Metabolic rates have been obtained and published for 4 of 7 marine turtle species, but not for all life stages for all of these species. Studies of marine turtle metabolism have ranged from straightforward MR measurements of a few individuals to use of innovative techniques to estimate energy expenditure of natural activities and for applications to marine turtle energetics and diving physiology. Comparisons of allometric relationships between resting MR (RMR) and body mass for leatherbacks (Dermochelys coriacea), green turtles (Chelonia mydas), other reptiles, and mammals revealed no differences between leatherbacks and green turtles, nor between those species and other reptiles, but significant differences with mammals. In addition, we synthesized research on the thermal biology of the leatherback turtle, which ranges from temperate to tropical waters, and concluded that leatherbacks achieve and maintain substantial differentials between body and ambient temperatures in varied thermal environments through an integrated balance of adaptations for heat production (e.g., adjustments of MR) and retention. Finally, we recommend that future research should 1) address remaining data gaps in current knowledge of MRs of some species, 2) apply MR measurements to important physiological, ecological, and conservation topics, 3) investigate cellular metabolism of marine turtles, and 4) focus on quantification of at-sea energy expenditure incurred by marine turtles during natural activities.
    Journal of Experimental Marine Biology and Ecology. 01/2008;
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    ABSTRACT: Since 1943, a total of 40 leatherbacks have been documented in neritic and offshore waters of the Gulf of California, Mexico: 13 as fisheries by-catch, 11 in indigenous ceremonies, 8 coastal strandings, 4 at-sea sightings, 3 observed by fishing fleets, and 1 via satellite telemetry. Leatherback hatchlings were observed on 3 occasions in the northern Gulf of California. The range of curved carapace lengths for nonhatchling leatherbacks was 113 to 160 cm curved carapace length (mean = 139 ± 12 cm). All but 1 leatherback were reported between November and May, a period of cooler water temperatures for the region.
    Chelonian Conservation and Biology 01/2009; · 0.74 Impact Factor


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