Pleated turtle escapes the box – shape changes in Dermochelys coriacea

Abstract

SUMMARYTypical chelonians have a rigid carapace and plastron that form a box-like structure that constrains several aspects of their physiology and ecology. The leatherback sea turtle, Dermochelys coriacea, has a flexible bony carapace strengthened by seven longitudinal ridges, whereas the plastron is reduced to an elliptical outer bony structure, so that the ventrum has no bony support. Measurements of the shell were made on adult female leatherbacks studied on the feeding grounds of waters off Nova Scotia (NS) and on breeding beaches of French Guiana (FG) to examine whether foraging and/or breeding turtles alter carapace size and/or shape. NS turtles exhibited greater mass and girth for a given curved carapace length (CCL) than FG turtles. Girth:CCL ratios rose during the feeding season, indicating increased girth. Measurements were made of the direct (straight) and surface (curved) distances between the medial longitudinal ridge and first right-hand longitudinal ridge (at 50% CCL). In NS turtles, the ratio of straight to curved inter-ridge distances was significantly higher than in FG turtles, indicating distension of the upper surfaces of the NS turtles between the ridges. FG females laid 11 clutches in the breeding season; although CCL and curved carapace width remained stable, girth declined between each nesting episode, indicating loss of mass. Straight to curved inter-ridge distance ratios did not change significantly during the breeding season, indicating loss of dorsal blubber before the onset of breeding. The results demonstrate substantial alterations in size and shape of female D. coriacea over periods of weeks to months in response to alterations in nutritional and reproductive status.

Behavioral and metabolic contributions to thermoregulation in freely swimming leatherback turtles at high latitudes

“…Adult leatherbacks typically weigh 250-600 kg, and a small surface area-to-volume ratio combined with extensive fat deposits beneath the shell and throughout the head and neck region predisposes them to heat retention (Davenport et al, 2009a;Davenport et al, 2011). Vascular heat exchangers at the base of the flippers (Greer et al, 1973) and blood flow adjustments (Bostrom et al, 2010) permit tight control of heat loss at the extremities, and a vascular plexus lining the trachea minimizes respiratory heat loss (Davenport et al, 2009b).…”

Pre-nesting Movements of Leatherback Sea Turtles, Dermochelys coriacea, in the Western Atlantic

“…The foraging grounds of Atlantic Canada have been identified as critical habitat for mature leatherbacks (James et al, 2006), and both morphometric and physiological indicators have been used to determine that leatherbacks are capital breeders (James et al, 2005b;Davenport et al, 2011;Plot et al, 2013). Throughout the nesting season, leatherbacks rely on energy stores and become anorexic (Plot et al, 2013).…”

Crying a river: how much salt-laden jelly can a leatherback turtle really eat?

“…Clutches had a mean mass of about 5 kg, most of which was water (Wallace et al, 2007), so this first clutch (of <11) had negligible effect on the 100 kg difference. Body girth and mass increase during the period on the foraging grounds (Davenport et al, 2011). However, it is probable that some of the difference in mass between breeding and foraging areas reflects foraging at lower latitudes and at depth .…”

“…However, for adult Dermochelys, TGCT must be of the order of a few hours. Although leatherbacks have much more ability than other turtles to vary their body volume (Davenport et al, 2011), it is improbable that they can store more than 4-6 hours' worth (roughly 22-32% body volume given a 73% body mass day −1 intake rate) of jellyfish intake. This is consistent with known high rates of digestion of gelatinous prey (Jackson et al, 1987;Arai, 2005) but implies a high rate of peristaltic activity.…”

“…However, any estimate must be compatible with separate observations that Nova Scotian female leatherbacks are about 33% heavier (ca. 100 kg) during the summer feeding season (approximately 100 days long) than females from the same population weighed after they had laid the first clutch of the breeding season (Davenport et al, 2011), implying hyperphagia and capital breeding. This difference results from the laying down of blubber (containing about 33 kJ g −1 wet mass, given a 90% fat content).…”