Thermal and biochemical characteristics of the lipids of the leatherback turtleDermochelys coriacea: evidence of endothermy

Abstract

Unlike other sea turtles, the leatherback Dermochelys coriacea forages widely in temperate waters during summer and dives to abyssal depths (>1000 m) where temperatures are low. There is strong anatomical plus limited physiological evidence in favour of at least facultative endothermy. The lipids of leatherbacks exhibit features which are consistent with maintenance of a core temperature above ambient levels when in cool waters. The lipid of flipper adipose tissue freezes at a lower temperature than lipids extracted from the blubber lining carapace and plastron. Lipid freezing points in leatherbacks are lower than for tropical caimans or terrestrial sheep, but higher than for lipids taken from the blubber of a grey seal. Leatherback adipose tissues show levels of unsaturation in neutral lipid fractions intermediate between those of seals and sheep.

Pleated turtle escapes the box – shape changes in Dermochelys coriacea

“…This presumably reflects the deposition of blubber beneath the dorsal skin (which stretches) evident in dissections of stranded and drowned animals at high latitude (e.g. Davenport et al, 1990). Interestingly, the measured shape of the dorsal surface does not change during the breeding season itself, even though the turtle may lay ≤11 clutches and show marked reductions in girth.…”

“…The ossicles of the carapace are lined ventrally with blubber. In a large male leatherback the skin was at least 1cm thick and the blubber 2.8cm thick in the plastral region, 2.5cm thick in the carapacial region and approximately 5cm thick at the bases of the four limbs (Davenport et al, 1990). Given the absence of bony elements in most of the plastron and a flexible carapace, the leatherback anatomy delivers a compliant structure already known to expand and compress in the ventral region during respiration (Lutcavage and Lutz, 1997).…”

“…Adult D. coriacea are well known to have core body temperatures elevated over ambient when in cool water (e.g. off Newfoundland and Nova Scotia) by virtue of large size (gigantothermy), blubber composition and countercurrent heat exchangers (Frair et al, 1972;Paladino et al, 1990;Davenport et al, 1990;James and Mrosovsky, 2004). Bostrom et al have recently shown that even small juvenile turtles (16-37kg) can sustain temperature gradients between the body and the external environment (Bostrom et al, 2010), so that D. coriacea is truly endothermic.…”

Kemp's Ridley Sea Turtle Saga and Setback: Novel Analyses of Cumulative Hatchlings Released and Time-Lagged Annual Nests in Tamaulipas, Mexico

“…For example, leatherbacks have a countercurrent circulatory system (Greer et al 1973), 12 a thick layer of insulating fat (Davenport et al 1990;Goff and Lien 1988), gigantothermy (Paladino et al 1990), 13 and they can increase their body temperature through increased metabolic activity (Bostrom and Jones 2007;Southwood et al 2005). These adaptations allow leatherbacks to be comfortable in a wide range of temperatures and to travel further than any other sea turtle species (NMFS and USFWS 1995).…”

Prey landscapes help identify potential foraging habitats for leatherback turtles in the NE Atlantic

“…Female leatherbacks foraging in northwest Atlantic waters (15 to 16.7°C) have been shown to support core body temperatures 8.2 ± 2.4°C (mean ± SD) above ambient sea temperature (James & Mrosovsky 2004). 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.…”