Regional endothermy in the sea turtle, Chelonia mydas

Standora, Edward A.; Spotila, James R.; Foley, Robert E.

doi:10.1016/0306-4565(82)90006-7

Cited by 59 publications

(32 citation statements)

References 26 publications

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“…Some species such as green (C. mydas) and loggerhead (Caretta caretta) turtles range from equatorial regions to colder areas of the northern or southern oceans [16], and larger body size also becomes advantageous in cold waters because lower surface area to volume ratios reduce heat lost to the environment. Arguing against large size purely as a thermoregulatory adaptation is the observation that the leatherback turtle can use changes in blood flow to maintain body temperatures above ambient in colder waters [16,17]. Furthermore, the largest turtles to have ever lived, such as the 4.6 m Archelon ischyros [18], inhabited Mesozoic seas that would have been much warmer than today's oceans [19][20][21].…”

Section: Discussionmentioning

confidence: 99%

The evolution of island gigantism and body size variation in tortoises and turtles

2011

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Extant chelonians (turtles and tortoises) span almost four orders of magnitude of body size, including the startling examples of gigantism seen in the tortoises of the Galapagos and Seychelles islands. However, the evolutionary determinants of size diversity in chelonians are poorly understood. We present a comparative analysis of body size evolution in turtles and tortoises within a phylogenetic framework. Our results reveal a pronounced relationship between habitat and optimal body size in chelonians. We found strong evidence for separate, larger optimal body sizes for sea turtles and island tortoises, the latter showing support for the rule of island gigantism in non-mammalian amniotes. Optimal sizes for freshwater and mainland terrestrial turtles are similar and smaller, although the range of body size variation in these forms is qualitatively greater. The greater number of potential niches in freshwater and terrestrial environments may mean that body size relationships are more complicated in these habitats.

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Section: Discussionmentioning

confidence: 99%

The evolution of island gigantism and body size variation in tortoises and turtles

2011

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“…4), probably because they did not gain the required heat due to shallow radiation angles and lower air temperatures (Boyer, 1965). Further support for the heating function of some ESTs is given by the correlation between body mass and EST duration, as it would take longer to heat up larger turtles (Boyer, 1965;Standora et al, 1982).…”

Section: Light-dependent Functions Of Estmentioning

confidence: 99%

When surfacers do not dive: multiple significance of extended surface times in marine turtles

Hochscheid

Bentivegna

Hamza

et al. 2010

Journal of Experimental Biology

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SUMMARYMarine turtles spend more than 90% of their life underwater and have been termed surfacers as opposed to divers. Nonetheless turtles have been reported occasionally to float motionless at the surface but the reasons for this behaviour are not clear. We investigated the location, timing and duration of extended surface times (ESTs) in 10 free-ranging loggerhead turtles (Caretta caretta) and the possible relationship to water temperature and diving activity recorded via satellite relay data loggers for 101-450 days. For one turtle that dived only in offshore areas, ESTs contributed 12% of the time whereas for the other turtles ESTs contributed 0.4-1.8% of the time. ESTs lasted on average 90 min but were mostly infrequent and irregular, excluding the involvement of a fundamental regulatory function. However, 82% of the ESTs occurred during daylight, mostly around noon, suggesting a dependence on solar radiation. For three turtles, there was an appreciable (7°C to 10.5°C) temperature decrease with depth for dives during periods when ESTs occurred frequently, suggesting a re-warming function of EST to compensate for decreased body temperatures, possibly to enhance digestive efficiency. A positive correlation between body mass and EST duration supported this explanation. By contrast, night-active turtles that exceeded their calculated aerobic dive limits in 7.6-16% of the dives engaged in nocturnal ESTs, probably for lactate clearance. This is the first evidence that loggerhead turtles may refrain from diving for at least two reasons, either to absorb solar radiation or to recover from anaerobic activity.

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“…The extreme body size of the leatherback turtle Dermochelys coriacea and its previously studied gigantothermy (Paladino et al 1990, Davenport 1998) make it desirable to differentiate between the families Dermochelidae and the smaller Cheloniidae. However, even species of the latter family are capable of maintaining their body temperatures above that of the surrounding water during activity, with the huge pectoralis muscles being up to 7°C above water temperature (Heath & McGinnis 1980, Standora et al 1982, Spotila & Standora 1985, Sato et al 1994. Animals the size of sea turtles have high, internal, heat-storage capacities and therefore large thermal inertia.…”

Section: Introductionmentioning

confidence: 99%

Cold-blooded divers: temperature-dependent dive performance in the wild hawksbill turtle Eretmochelys imbricata

Storch

Wilson²,

Hillis-Starr³

et al. 2005

Mar. Ecol. Prog. Ser.

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Sea turtles are diving ectotherms that are influenced by the temperature of the ambient water, although swimming activity can temper this influence via increased body temperatures enhanced by the thermal inertia of these large animals. We successfully equipped 3 nesting hawksbill turtles Eretmochelys imbricata with time-depth recorders (TDRs) to monitor water temperature and dive depth over the duration of the re-migration interval between 2 successive nesting seasons. Data sets for up to 22 mo were obtained, showing fluctuations in water temperature over the seasons. Nocturnal dive behaviour of the turtles at their foraging grounds revealed an increase in dive duration with decreasing water temperatures in winter. A model is provided to estimate dive duration for the range of temperatures experienced by this species in the wild. The data on vertical velocity during ascent and descent phases as a parameter for activity failed to show thermal dependence. It is concluded that changes in water temperature have an effect on the behavioural ecology of hawksbill turtles.

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Regional endothermy in the sea turtle, Chelonia mydas

Cited by 59 publications

References 26 publications

The evolution of island gigantism and body size variation in tortoises and turtles

The evolution of island gigantism and body size variation in tortoises and turtles

When surfacers do not dive: multiple significance of extended surface times in marine turtles

Cold-blooded divers: temperature-dependent dive performance in the wild hawksbill turtle Eretmochelys imbricata

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