Optimising the hatching success of artificially incubated eggs for use in a conservation program for the western saw-shelled turtle (

Artificial incubation of eggs and the release of hatchlings into the wild is a common conservation intervention designed to augment threatened turtle populations. We investigate a range of incubation temperatures to establish an optimal temperature for maximum hatching success of western saw-shelled turtle (Myuchelys bellii) eggs. We report on the influence of incubation temperature on incubation duration and hatching success and describe two experimental incubation methods which, for the same incubation temperature (27°C), resulted in 77% and 97% hatching success, respectively. Eggs were incubated at constant temperatures (27°C, 28°C and 29°C) to determine the influence of temperature on incubation period, hatchling morphology and external residual yolk. Incubation duration was negatively correlated with incubation temperature. We report on the morphology of eggs and hatchlings and show that their dimensions are positively correlated with maternal adult size and mass. A constant incubation temperature of 27°C produced the highest hatching success and smallest external residual yolk on hatching and is therefore recommended for incubation of eggs for population reinforcement programs. Our study is the first to optimise artificial incubation procedures for M. bellii and will be a valuable resource for M. bellii and other threatened freshwater turtle conservation initiatives.

Divergent incubation temperature effects on thermal sensitivity of hatchling performance in two different latitudinal populations of an invasive turtle

The incubation temperature for embryonic development affects several aspects of hatchling performance, but its impact on the thermal sensitivity of performance attributes remains poorly investigated. In the present study, Trachemys scripta elegans hatchlings from two different latitudinal populations were collected to assess the effects of different incubation temperatures on the locomotor (swimming speed) and physiological (heart rate) performances, and the thermal sensitivity of these two attributes. The incubation temperature significantly affected the examined physiological traits. Hatchling turtles produced at low incubation temperature exhibited relatively higher cold tolerance (lower body temperatures at which the animals lose the ability to escape from the lethal conditions), and reduced heart rate and swimming speed. Furthermore, the effect of incubation temperature on the thermal sensitivity of swimming speed differed between the low- and high-latitude populations. At relatively high incubation temperatures, the high-latitude hatchling turtles exhibited reduced thermal sensitivities of swimming speed than those of the low-latitude ones. Reduced thermal sensitivity of locomotor performance together with high cold tolerance, exhibited by the high-latitude hatchling turtles potentially reflected local adaptation to relatively colder and more thermally-variable environments.

Effects of temperature and exercise on metabolism of three species of Australian freshwater turtles: implications for responses to climate change

Oxygen consumption () of Chelodina expansa, C. longicollis and Emydura macquarii (Pleurodira: Chelidae) was measured at rest and during induced exercise at 8, 13, 18, 22, 26, 30 and 34°C. Resting varied significantly among species, being lowest in C. expansa, which is the most sedentary of the three species in nature, and highest in E. macquarii, which is the most energetic, but active did not differ significantly among the three species overall. For both Chelodina species, resting was appreciably lower than expected from regression of on body mass for non-marine turtles globally, a result that reinforces previous evidence of low resting metabolism in Australian chelid turtles. Active of all three species at higher temperatures was similar to reported for active freshwater cryptodires. Resting of all three species increased similarly with temperature, but active and aerobic scope did not. In C. expansa and E. macquarii, active and aerobic scope increased over the full temperature range assessed but in C. longicollis these variables reached a plateau above 22°C. Projected increases in freshwater temperatures in south-eastern Australia as a result of global warming are likely to enhance activity, feeding and growth of the three species (subject to food availability), especially in cooler seasons for C. longicollis and warmer seasons for C. expansa and E. macquarii. However, other aspects of predicted climate change, especially increased drought, are likely to be detrimental.