An XX/XY sex microchromosome system in a freshwater turtle, Chelodina longicollis (Testudines: Chelidae) with genetic sex determination

2006 ◽  
Vol 14 (2) ◽  
pp. 139-150 ◽  
Author(s):  
Tariq Ezaz ◽  
Nicole Valenzuela ◽  
Frank Grützner ◽  
Ikuo Miura ◽  
Arthur Georges ◽  
...  
Keyword(s):  
Sex Determination ◽  
Freshwater Turtle ◽  
Chelodina Longicollis

Ecological and physiological impacts of salinisation on freshwater turtles of the lower Murray River

2012 ◽  
Vol 39 (8) ◽  
pp. 705 ◽  
Author(s):  
Deborah S. Bower ◽  
Clare E. Death ◽  
Arthur Georges
Keyword(s):  
Saline Lake ◽  
South Australia ◽  
Freshwater Turtle ◽  
Plasma Sodium ◽  
Freshwater Species ◽  
Freshwater Turtles ◽  
Brackish Lake ◽  
Ecological Processes ◽  
Murray River ◽  
Chelodina Longicollis

Context The increasing intensity and extent of anthropogenically mediated salinisation in freshwater systems has the potential to affect freshwater species through physiological and ecological processes. Determining responses to salinisation is critical to predicting impacts on fauna. Aims We aimed to quantify the response of wild-caught turtles from freshwater lakes that had become saline in the lower Murray River catchment. Methods Plasma electrolytes of all three species of freshwater turtle from South Australia were compared among two freshwater sites (Horseshoe Lagoon and Swan Reach), a brackish lake (Lake Bonney) and a saline lake (Lake Alexandrina). Key results Chelodina longicollis, C. expansa and Emydura macquarii from a brackish lake had higher concentrations of plasma sodium and chloride than those from freshwater habitats. However, osmolytes known to increase under severe osmotic stress (urea and uric acid) were not elevated in brackish sites. Turtles from the highly saline lake were colonised by an invasive marine worm which encased the carapace and inhibited limb movement. Conclusions Freshwater turtles in brackish backwaters had little response to salinity, whereas the C. longicollis in a saline lake had a significant physiological response caused by salt and further impacts from colonisation of marine worms. Implications Short periods of high salinity are unlikely to adversely affect freshwater turtles. However, secondary ecological processes, such as immobilisation from a marine worm may cause unexpected impacts on freshwater fauna.

Freshwater turtle hatchlings that stay in the nest: strategists or prisoners?

2018 ◽  
Vol 66 (1) ◽  
pp. 34 ◽  
Author(s):  
Bruce C. Chessman
Keyword(s):  
Adaptive Strategy ◽  
Freshwater Turtle ◽  
Nest Construction ◽  
Oxbow Lakes ◽  
Freshwater Turtles ◽  
Red Foxes ◽  
Fine Grained ◽  
Delayed Emergence ◽  
Hard Soil ◽  
Chelodina Longicollis

Hatchlings of several species of freshwater turtles have been reported to remain in subterranean nests for extended periods following hatching from the egg. It has been suggested that this delayed emergence, including overwintering in the nest in populations at temperate latitudes, is an evolved adaptation that enables hatchlings to enter the aquatic environment at the most propitious time for survival and growth. I monitored nests of a temperate-zone population of the freshwater Australian eastern long-necked turtle (Chelodina longicollis) for up to a year after nest construction in fine-grained soils adjacent to oxbow lakes and farm ponds. An estimated 84% of nests were preyed on, probably mainly by non-native red foxes (Vulpes vulpes), whereas hatchlings emerged from autumn to spring from an estimated 5% of nests. The remaining 11% of nests were neither preyed on nor had emergence by a year after nest construction. Live hatchlings were present in some nests with no emergence up to 10 months after nest construction, but substantial numbers of dead hatchlings were present beyond nine months. It therefore seems unlikely that emergence occurs more than a year after nest construction. Delayed emergence of this species in this environment appears less likely to be an adaptive strategy than to be a consequence of imprisonment in the nest by hard soil that is difficult for hatchlings to excavate.

Hatchling Sex Ratios are Independent of Temperature in Field Nests of the Long-necked Turtle, Chelodina longicollis (Testudinata : Chelidae)

1991 ◽  
Vol 18 (2) ◽  
pp. 225 ◽  
Author(s):  
M Palmer-Allen ◽  
F Beynon ◽  
a Georges
Keyword(s):  
Sex Determination ◽  
Constant Temperature ◽  
Sex Chromosomes ◽  
Sex Ratios ◽  
Seasonal Trend ◽  
Temperature Dependent ◽  
Sharp Drop ◽  
Heteromorphic Sex Chromosomes ◽  
Chelodina Longicollis ◽  
Incubation Temperatures

Eastern long-necked turtles, Chelodina longicollis, are known to lack heteromorphic sex chromosomes and to lack temperature-dependent sex determination when incubated under constant conditions. This study determined whether sex ratios of hatchlings emerging from natural nests of C. longicollis were different from that expected from constant temperature experiments. Temperatures in the eight nests monitored varied considerably each day (by 1.7-12.6�C), with eggs at the top of the nest experiencing the greatest variation (mean range 9.0�C) and eggs at the bottom experiencing least variation (mean range 5.3�C). Temperatures experienced by the top and bottom eggs differed by as much as 5.7�C at any one time. No monotonic seasonal trend was evident, but rainfall caused a sharp drop in nest temperatures. Sex ratios in hatchlings from 14 field nests of C. longicollis did not differ significantly from 1:1, a result in agreement with previous studies conducted at constant incubation temperatures in the laboratory.

scholarly journals The role of Cyp19a1 in female pathway of a freshwater turtle (Mauremys reevesii) with temperature-dependent sex determination

2021 ◽  
Author(s):  
Pengfei Wu ◽  
Xifeng Wang ◽  
Fei Gao ◽  
Weiguo Du
Keyword(s):  
Sex Determination ◽  
Sex Differentiation ◽  
Critical Role ◽  
Temperature Shift ◽  
Vital Role ◽  
Freshwater Turtle ◽  
Temperature Dependent ◽  
Female Sex ◽  
Determination Process ◽  
Sexually Dimorphic Expression

The molecular mechanism of temperature-dependent sex determination (TSD) in reptiles has been drawn great interest from biologists for several decades. However, which genetic factors are essential for TSD remain elusive, especially for the female sex determination process. Cyp19a1, encodes an enzyme of aromatase catalyzing the conversion of testosterone to estrogen, has been confirmed to modulate steroid hormones involved in the sexual differentiation of many species, but whether it has a critical role in determining the gonadal sexual fate in TSD is still to be elucidated. Here, we identified that Cyp19a1 expression exhibited a temperature-dependent, sexually dimorphic expression pattern, preceding gonadal sex differentiation in a TSD turtle Mauremys reevesii. Cyp19a1 expression in gonads increased dramatically when embryos developed at high female-producing temperatures (FPT), but were extremely low throughout embryogenesis at low male-producing temperatures (MPT). Cyp19a1 expression increased rapidly in response to the temperature shift from MPT to FPT in developing gonads. The sexual phenotype of turtles was successfully reversed by aromatase inhibitor treatment at FPT, and by estrogen treatment at MPT, accompanied with the rapid upregulation of Cyp19a1. These results demonstrate that Cyp19a1 is essential for the female sex determination process in M. reevesii, indicating its vital role in the female pathway of TSD.

Declines of freshwater turtles associated with climatic drying in Australia

2011 ◽  
Vol 38 (8) ◽  
pp. 664 ◽  
Author(s):  
Bruce C. Chessman
Keyword(s):  
River Flow ◽  
Freshwater Turtle ◽  
Severe Drought ◽  
Freshwater Turtles ◽  
Catch Per Unit Effort ◽  
Unit Effort ◽  
Murray River ◽  
Floodplain Inundation ◽  
Global Impacts ◽  
Chelodina Longicollis

Context While much attention has been paid to the effects of global temperature increases on the geographical ranges and phenologies of plants and animals, less is known about the impacts of climatically driven alteration of water regimes. Aims To assess how three species of freshwater turtle in Australia’s Murray–Darling Basin have responded to long-term decline in river flow and floodplain inundation due to climatic drying and water diversions. Methods Turtle populations were sampled in a section of the Murray River and its floodplain in 1976–82 following a wet period and in 2009–11 at the end of the most severe drought on record. Catch per unit effort, proportional abundance in different habitat types and population structure were assessed in both periods. Key results Catch per unit effort in baited hoop nets declined by 91% for the eastern snake-necked turtle (Chelodina longicollis) and 69% for the Murray turtle (Emydura macquarii), but did not change significantly for the broad-shelled turtle (Chelodina expansa). In addition, total catches from a range of sampling methods revealed a significantly reduced proportion of juvenile C. longicollis and E. macquarii in 2009–11, suggesting a fall in recruitment. Key conclusions The decline of C. longicollis was likely due mainly to drought-induced loss of critical floodplain habitat in the form of temporary water bodies, and that of E. macquarii to combined effects of drought and predation on recruitment. C. expansa seems to have fared better than the other two species because it is less vulnerable to nest predation than E. macquarii and better able than C. longicollis to find adequate nutrition in the permanent waters that remain during extended drought. Implications Declining water availability may be a widespread threat to freshwater turtles given predicted global impacts of climate change and water withdrawals on river flows. Understanding how each species uses particular habitats and how climatic and non-climatic threats interact would facilitate identification of vulnerable populations and planning of conservation actions.

Sex-ratio bias across populations of a freshwater turtle (Testudines : Chelidae) with genotypic sex determination

2006 ◽  
Vol 33 (6) ◽  
pp. 475 ◽  
Author(s):  
Arthur Georges ◽  
Fiorenzo Guarino ◽  
Melissa White
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Sex Ratios ◽  
Single Species ◽  
Freshwater Turtle ◽  
Freshwater Turtles ◽  
Ratio Data ◽  
Adult Sex Ratio ◽  
Genotypic Sex Determination ◽  
The Impact

Adult sex ratios vary considerably among populations of single species and across years, but the best evidence is drawn from species with temperature-dependent sex determination. It is difficult to disentangle the effects of bias in the production of the sexes and the effects of a range of other factors contributing to biased adult sex ratios. In this paper, we survey sex ratios across populations of a species constrained to produce 1 : 1 offspring sex ratios by genotypic sex determination and show considerable variation in adult sex ratios. Raw adult sex ratios of Emydura macquarii emmottii were significantly biased in nine of the 11 populations examined. In all but one case, the bias was strongly in favour of males. Part of the bias in sex ratio was attributed to the differing ages of maturity of males and females – males mature younger than females – which leads to more male cohorts being included in the calculations of sex ratio than female cohorts. However, correcting for this effect brought the sex ratios of the populations closer to parity, as expected, and accounted for an overall 62% of the male surplus evident in the adult sex ratio. Even so, it was insufficient to explain the strong male bias (1.2–2.9) in five of the nine populations initially showing such bias. This provides support to those who advise caution in interpreting adult sex ratio data for freshwater turtles in the context of demography, sex allocation or evaluating the impact of climate change.

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