Pivotal temperature and predicted sex ratios for hatchling hawksbill turtles from Brazil

1999 ◽  
Vol 77 (9) ◽  
pp. 1465-1473 ◽  
Author(s):  
Matthew H Godfrey ◽  
Adriana F D'Amato ◽  
Maria  Marcovaldi ◽  
N Mrosovsky
Keyword(s):  
Low Temperatures ◽  
Sex Ratios ◽  
Sea Turtle ◽  
Temperature Dependent ◽  
Eretmochelys Imbricata ◽  
Conservation Implications ◽  
Incubation Duration ◽  
Incubation Temperatures ◽  
Hawksbill Turtles ◽  
Pivotal Temperature

Like all other species of sea turtle, the hawksbill turtle (Eretmochelys imbricata) exhibits temperature-dependent sexual differentiation, with high incubation temperatures producing females and low temperatures producing males. Relatively little is known about the sex ratios of hatchlings produced by nesting populations of hawksbill turtles. Here we estimate the overall seasonal sex ratios of hatchling hawksbill turtles produced in Bahia, Brazil, during 6 nesting seasons, based on incubation durations, pivotal temperature, and pivotal incubation duration. The overall sex ratio of hatchlings produced in Bahia from 1991-1992 through 1996-1997 was estimated to be >90% female, which is more female-biased than estimated sex ratios of hatchling loggerhead turtles from Bahia and Florida, U.S.A. The biological and conservation implications of skewed sex ratios are discussed.

scholarly journals Feminization of hawksbill turtle hatchlings in the twenty-first century at an important regional nesting aggregation

2021 ◽  
Vol 44 ◽  
pp. 149-158
Author(s):  
M Chatting ◽  
S Hamza ◽  
J Al-Khayat ◽  
D Smyth ◽  
S Husrevoglu ◽  
...  
Keyword(s):  
Climate Change ◽  
Sex Ratios ◽  
First Century ◽  
Climate Data ◽  
Temperature Dependent ◽  
Eretmochelys Imbricata ◽  
Climate Forecasts ◽  
The Face ◽  
Incubation Temperatures ◽  
Hawksbill Turtles

Projected climate change is forecasted to have significant effects on biological systems worldwide. Marine turtles in particular may be vulnerable, as the sex of their offspring is determined by their incubating temperature, termed temperature-dependent sex determination. This study aimed to estimate historical, and forecast future, primary sex ratios of hawksbill turtle Eretmochelys imbricata hatchlings at an important nesting ground in northeastern Qatar. Incubation temperatures from the Arabian/Persian Gulf were measured over 2 nesting seasons. Climate data from same period were regressed with nest temperatures to estimate incubation temperatures and hatchling sex ratios for the site from 1993 to 2100. Future hatchling sex ratios were estimated for 2 climate forecasts, one mid-range (SSP245) and one extreme (SSP585). Historical climate data showed female-biased sex ratios of 73.2 ± 12.1% from 1993 to 2017. Female biases from 2018 to 2100 averaged 85.7% ± 6.7% under the mid-range scenario and 87.9% ± 5.4% under the high-range scenario. In addition, predicted female hatchling production was >90% from 2054 and 2052 for SSP245 and SSP585, respectively. These results show that hawksbill primary sex ratios in Qatar are at risk of significant feminization by the year 2100 and that hawksbill turtle incubation temperatures in an extreme, understudied environment are already comparable to those predicted in tropical rookeries during the latter half of the 21st century. These results can help conservationists predict primary sex ratios for hawksbill turtles in the region in the face of 21st-century climate change.

Pivotal and beach temperatures for hawksbill turtles nesting in Antigua

1992 ◽  
Vol 70 (10) ◽  
pp. 1920-1925 ◽  
Author(s):  
N. Mrosovsky ◽  
Anna Bass ◽  
Lynn A. Corliss ◽  
James I. Richardson ◽  
Thelma H. Richardson
Keyword(s):  
Sex Ratios ◽  
Eretmochelys Imbricata ◽  
Hawksbill Turtles ◽  
Pivotal Temperature

Eggs of hawksbill turtles, Eretmochelys imbricata, from Antigua were incubated at constant tempe ratures. The pivotal temperature (the temperature at which 50% of each sex is produced) for the sample was estimated to be 29.2 °C. Sand temperatures at the depth of turtle nests were recorded over two nesting seasons at Pasture Bay, Antigua. Although sand temperatures were sometimes higher than the pivotal temperature, more often they were lower. On this basis, it is unlikely that hatchling hawksbill turtles in this area have the highly female-biased sex ratios reported for some other reptiles.

scholarly journals Temperature-dependent sex-biased embryo mortality in a bird

2008 ◽  
Vol 275 (1652) ◽  
pp. 2703-2706 ◽  
Author(s):  
Yvonne A Eiby ◽  
Jessica Worthington Wilmer ◽  
David T Booth
Keyword(s):  
Low Temperatures ◽  
Incubation Temperature ◽  
Sex Ratios ◽  
Molecular Sexing ◽  
Temperature Dependent ◽  
Female Embryo ◽  
Male Embryo ◽  
Diverse Range ◽  
Embryo Mortality ◽  
Incubation Temperatures

Sex ratios have important evolutionary consequences and are often biased by environmental factors. The effect of developmental temperature on offspring sex ratios has been widely documented across a diverse range of taxa but has rarely been investigated in birds and mammals. However, recent field observations and artificial incubation experiments have demonstrated that the hatching sex ratio of a megapode, the Australian brush-turkey ( Alectura lathami ), varied with incubation temperature; more females hatched at high incubation temperatures and more males hatched at low temperatures. Here, we investigated the causes of this temperature-dependent sex-biasing system. Molecular sexing of chicks and embryos confirmed that male embryo mortality was greater at high temperatures while female embryo mortality is greater at low temperatures, with mortality in both sexes similar at intermediate incubation temperatures. Temperature-dependent sex-biased embryo mortality represents a novel mechanism of altering sex ratios in birds. This novel mechanism, coupled with the unique breeding biology of the brush-turkey, offers a potentially unparalleled opportunity in which to investigate sex allocation theory in birds.

Sex determination in Cagle's map turtle: implications for evolution, development, and conservation

1991 ◽  
Vol 69 (10) ◽  
pp. 2693-2696 ◽  
Author(s):  
Thane Wibbels ◽  
Flavius C. Killebrew ◽  
David Crews
Keyword(s):  
North America ◽  
Reproductive Success ◽  
Sex Ratio ◽  
Sex Determination ◽  
Low Temperatures ◽  
River System ◽  
Temperature Dependent ◽  
Interspecific Variations ◽  
Incubation Temperatures ◽  
Pivotal Temperature

Sex determination was investigated in Cagle's map turtle, Graptemys caglei, which has a restricted distribution which is the southernmost of all Graptemys species. This species exhibits temperature-dependent sex determination, with high incubation temperatures producing only females and low temperatures producing only males. The estimated pivotal temperature (approximately 30.0 °C) is higher than those reported for other species of Graptemys in North America; however, the interspecific variations in pivotal temperature are small (approximately 0.5–1.0 °C). Temperature appears to affect the ovarian or testicular nature of the gonads in an "all or none" fashion, but exerts a graded effect on the length of ovaries. In addition, temperature appears to exert a graded effect on the regression of the oviducts in males. The occurrence of temperature-dependent sex determination in this species is also of conservational importance, since alterations to a single river system could potentially impact the reproductive success of this species by changing nest temperatures and, thus, population sex ratio(s).

Validation of incubation duration as an index of the sex ratio of hatchling sea turtles

1999 ◽  
Vol 77 (5) ◽  
pp. 831-835 ◽  
Author(s):  
N Mrosovsky ◽  
Cecília Baptistotte ◽  
Matthew H Godfrey
Keyword(s):  
Sex Ratio ◽  
High Temperatures ◽  
Low Temperatures ◽  
Sea Turtles ◽  
Sex Ratios ◽  
Caretta Caretta ◽  
Turtle Species ◽  
Loggerhead Turtles ◽  
Incubation Duration

One method of estimating the sex ratio of hatchling sea turtles is to use the incubation duration. Long and short durations imply low and high temperatures, respectively. In turtle species whose sex is determined by temperature, males are produced at low temperatures and females at high temperatures. This study assesses the validity of using incubation duration to estimate the sex ratio. Samples of hatchling loggerhead turtles (Caretta caretta) were collected from nests with known incubation durations, and sex was ascertained by means of histology. The sex ratio of groups of nests determined by histology was compared with that predicted from previous relationships between incubation duration and sex ratio. For conditions causing relatively long or relatively short incubation durations, the sex ratio could be predicted with considerable accuracy. For conditions causing durations nearer to the pivotal duration (that which gives 50% of each sex), predictions could be off by 10%, depending on the distribution of incubation durations, but it was still possible to determine whether ratios were highly skewed or approximately balanced. Estimating sex ratios of hatchling sea turtles from incubation durations is simple, cheap, and can be used retrospectively.

scholarly journals Lipid profiling suggests species specificity and minimal seasonal variation in Pacific Green and Hawksbill Turtle plasma

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0253916
Author(s):  
Chelsea E. Clyde-Brockway ◽  
Christina R. Ferreira ◽  
Elizabeth A. Flaherty ◽  
Frank V. Paladino
Keyword(s):  
Sea Turtles ◽  
Multiple Reaction Monitoring ◽  
Chelonia Mydas ◽  
Sea Turtle ◽  
Lipid Classes ◽  
Plasma Samples ◽  
Lipid Profiling ◽  
Eretmochelys Imbricata ◽  
Species Specific ◽  
Hawksbill Turtles

In this study, we applied multiple reaction monitoring (MRM)-profiling to explore the relative ion intensity of lipid classes in plasma samples from sea turtles in order to profile lipids relevant to sea turtle physiology and investigate how dynamic ocean environments affect these profiles. We collected plasma samples from foraging green (Chelonia mydas, n = 28) and hawksbill (Eretmochelys imbricata, n = 16) turtles live captured in North Pacific Costa Rica in 2017. From these samples, we identified 623 MRMs belonging to 10 lipid classes (sphingomyelin, phosphatidylcholine, free fatty acid, cholesteryl ester, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol, phosphatidylethanolamine, ceramide, and triacylglyceride) and one metabolite group (acyl-carnitine) present in sea turtle plasma. The relative ion intensities of most lipids (80%) were consistent between species, across seasons, and were not correlated to body size or estimated sex. Of the differences we observed, the most pronounced was the differences in relative ion intensity between species. We identified 123 lipids that had species-specific relative ion intensities. While some of this variability is likely due to green and hawksbill turtles consuming different food items, we found indications of a phylogenetic component as well. Of these, we identified 47 lipids that varied by season, most belonging to the structural phospholipid classes. Overall, more lipids (n = 39) had higher relative ion intensity in the upwelling (colder) season compared to the non-upwelling season (n = 8). Further, we found more variability in hawksbill turtles than green turtles. Here, we provide the framework in which to apply future lipid profiling in the assessment of health, physiology, and behavior in endangered sea turtles.

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 Feminization of Hawksbill Turtle hatchlings in the Twenty-first Century at an important Regional Nesting Aggregation

2021 ◽  
Author(s):  
Mark Chatting ◽  
Shafeeq Hamza ◽  
Jassim Al-Khayat ◽  
David Smyth
Keyword(s):  
Climate Change ◽  
At Risk ◽  
Sex Ratios ◽  
First Century ◽  
Climate Data ◽  
Eretmochelys Imbricata ◽  
Marine Turtles ◽  
Historical Climate ◽  
Incubation Temperatures ◽  
Nesting Aggregation

Projected climate change is forecasted to have significant effects on biological systems worldwide. Marine turtles in particular may be vulnerable, as the sex of their offspring is determined by their incubating temperature. This study is aimed to estimate historical and forecast future, primary sex ratios of hawksbill turtle hatchlings, Eretmochelys imbricata, in Qatar. Incubation temperatures were measured over two nesting seasons. Climate data from same period was regressed with nest temperatures to estimate incubation temperatures and hatchling sex ratios for the site from 1993 to 2100. Historical climate data showed female-biased sex ratios of 73.2 ±12.1% from 1993 to 2017. Female biases from 2018 to 2100 averaged 85.7% ±6.7%. In addition, predicted female hatchling production was >90% from 2054. These results show that hawksbill primary sex ratios in Qatar are at risk of significant feminization by the year 2100.

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