Anaerobic metabolism during dispersal of green and loggerhead turtle hatchlings

We measured activity levels, oxygen consumption, metabolic enzyme activity, breathing frequency, heart rate and blood chemistry variables of juvenile green turtles exposed to a laboratory simulation of subtropical winter and summer temperatures (17-26°C) and photoperiod (10.25·h:13.75·h to 14·h:10·h light:dark). The activity level of turtles had a significant effect on oxygen consumption and breathing frequency but there was no significant change in activity level between the summer and winter simulations. There was a moderate 24-27% decrease in oxygen consumption during exposure to winter conditions compared with summer conditions, but this difference was not statistically significant. Likewise, there was no statistically significant difference in breathing frequency between summer and winter simulations. Exposure to winter conditions did result in a significant decrease in activity of the aerobic enzyme citrate synthase. By contrast, activities of the glycolytic enzymes pyruvate kinase and lactate dehydrogenase were significantly higher in tissue collected during exposure to winter conditions compared with summer conditions. Citrate synthase, pyruvate kinase and lactate dehydrogenase had relatively low thermal dependence over the range of assay temperatures (15-30°C; Q10=1.44-1.69). Heart rate was 46-48% lower during the winter simulation compared with the summer simulation, and this difference was statistically significant. Exposure to winter conditions resulted in a significant decrease in plasma thyroxine and plasma proteins and a significant increase in plasma creatine phosphokinase and hematocrit. Overall, our results suggest that green turtles have a relatively low thermal dependence of metabolic rate over the range of temperatures commonly experienced at tropical to subtropical latitudes, a trait which allows them to maintain activity year-round.

Section: Discussionmentioning

confidence: 99%

Metabolic and cardiovascular adjustments of juvenile green turtles to seasonal changes in temperature and photoperiod

Southwood

Darveau

Jones

2003

“…Anaerobic metabolism is significant during the first 10-15 min of swimming as indicated by an increase in blood lactate concentration at a rate of approximately 1 μmol ml -1 of blood per minute in free-swimming green turtle hatchlings (Baldwin et al, 1989). Clearly this accumulation of lactate cannot continue indefinitely and the rapid decrease in stroke rate per power stroking bout during this time (Fig.…”

Section: Swimming Effortmentioning

confidence: 99%

“…However, measurement of blood lactate levels suggests that both aerobic and anaerobic metabolism power swimming within the first 10-15min of hatchlings entering the water (Baldwin et al, 1989). In a study that measured oxygen consumption (V O2 ) of hatchling sea turtles during and after the frenzy, V O2 during the frenzy period was found to be considerably greater than in the post-frenzy period (Wyneken, 1991;Wyneken, 1997).…”

Section: Introductionmentioning

confidence: 99%

Swimming for your life: locomotor effort and oxygen consumption during the green turtle (Chelonia mydas) hatchling frenzy

Booth

2009

SUMMARY Swimming effort and oxygen consumption of newly emerged green turtle Chelonia mydas hatchlings was measured simultaneously and continuously for the first 18 h of swimming after hatchlings entered the water. Oxygen consumption was tightly correlated to swimming effort during the first 12 h of swimming indicating that swimming is powered predominantly by aerobic metabolism. The patterns of swimming effort and oxygen consumption could be divided into three distinct phases: (1) the rapid fatigue phase from 0 to 2 h when the mean swim thrust decreased from 45 to 30 mN and oxygen consumption decreased from 33 to 18 ml h–1; (2) the slow fatigue phase from 2 to 12 h when the mean swim thrust decreased from 30 to 22 mN and oxygen consumption decreased from 18 to 10 ml h–1; and(3) the sustained effort phase from 12 to 18 h when mean swim thrust averaged 22 mN and oxygen consumption averaged 10 ml h–1. The decrease in mean swim thrust was caused by a combination of a decrease in front flipper stroke rate during a power stroking bout, a decrease in mean maximum thrust during a power stroking bout and a decrease in the proportion of time spent power stroking. Hence hatchlings maximise their swimming thrust as soon as they enter the water, a time when a fast swimming speed will maximise the chance of surviving the gauntlet of predators inhabiting the shallow fringing reef before reaching the relative safety of deeper water.

“…Bustard (1972) suggested that hatchlings may actively dig upwards through the nest column at any time during the day or night. Recent studies (Baldwin et al, 1989;Dial, 1987;Hamann et al, 2007) have used hatchlings' blood lactate concentration as an index of digging intensity, but were unable to relate these values to the overall energetics of the nest escape process. Another study addressed the energetics of nest escape in olive ridley (Lepidochelys olivcaea) hatchlings using the doubly labelled water (DLW) technique (Clusella Trullas et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Synchronous activity lowers the energetic cost of nest escape for sea turtle hatchlings

Rusli

Booth

Joseph

2016

A potential advantage of group movement in animals is increased locomotion efficiency. This implies a reduced energetic cost for individuals that occur in larger groups such as herds, flocks and schools. When chelonian hatchlings hatch in the underground nest with finite energy for their post-hatching dispersal phase, they face the challenge of minimizing energetic expenditure while escaping the nest. The term 'social facilitation' has been used to describe the combined digging effort of sea turtle hatchlings during nest escape. Given that in a normal clutch, a substantial part of the energy reserve within the residual yolk is used by hatchlings in the digging out process, a decreased cohort size may reduce the energy reserve available to cross the beach and sustain the initial swimming frenzy. This hypothesis was experimentally tested by varying cohort size in hatchling green turtles (Chelonia mydas) and measuring energy expenditure during the nest escape process using open-flow respirometry. The energetic cost of escaping through 40 cm of sand was calculated to vary between 4.4 and 28.3 kJ per individual, the cost decreasing as the number of individuals in the cohort increased. This represents 11-68% of the energy contained in a hatchling's residual yolk at hatching. The reduced energetic cost associated with large cohorts resulted from both a lower metabolic rate per individual and a shortened nest escape time. We conclude that synchronous digging activity of many hatchlings during nest escape evolved not only to facilitate rapid nest emergence but also to reduce the energetic cost to individuals.