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Temperature dependent sex determination

Graeme C Hays, Antonios D Mazaris, Gail Schofield, Jacques-Olivier Laloë
For species with temperature-dependent sex determination (TSD) there is the fear that rising temperatures may lead to single-sex populations and population extinction. We show that for sea turtles, a major group exhibiting TSD, these concerns are currently unfounded but may become important under extreme climate warming scenarios. We show how highly female-biased sex ratios in developing eggs translate into much more balanced operational sex ratios so that adult male numbers in populations around the world are unlikely to be limiting...
February 8, 2017: Proceedings. Biological Sciences
Edward Stallknecht Rice, Satomi Kohno, John St John, Son Pham, Jonathan Howard, Liana Lareau, Brendan L O'Connell, Glenn Hickey, Joel Armstrong, Alden Deran, Ian Fiddes, Roy N Platt, Cathy Gresham, Fiona McCarthy, Colin Kern, David Haan, Tan Phan, Carl Schmidt, Jeremy R Sanford, David A Ray, Benedict Paten, Louis J Guillette, Richard E Green
The American alligator, Alligator mississippiensis, like all crocodilians, has temperature-dependent sex determination, in which the sex of an embryo is determined by the incubation temperature of the egg during a critical period of development. The lack of genetic differences between male and female alligators leaves open the question of how the genes responsible for sex determination and differentiation are regulated. One insight into this question comes from the fact that exposing an embryo incubated at male-producing temperature to estrogen causes it to develop ovaries...
January 30, 2017: Genome Research
Nicole E Christie, Nicholas R Geist
Changes in temperature regimes are occurring globally due to climate change as well as habitat alterations. Temperatures are expected to continue to rise in the future, along with a greater degree of climatic instability. Such changes could have potentially serious consequences for oviparous ectotherms, especially those with temperature-dependent sex determination. To investigate the effects of temperature on a range of developmental phenomena in a population of western pond turtles (Emys marmorata), we placed temperature sensors on top of each layer of eggs within nests and recorded temperatures hourly through the first 2-3 mo of incubation...
January 2017: Physiological and Biochemical Zoology: PBZ
Mark C Mainwaring, Iain Barber, Denis C Deeming, David A Pike, Elizabeth A Roznik, Ian R Hartley
Nest building is a taxonomically widespread and diverse trait that allows animals to alter local environments to create optimal conditions for offspring development. However, there is growing evidence that climate change is adversely affecting nest-building in animals directly, for example via sea-level rises that flood nests, reduced availability of building materials, and suboptimal sex allocation in species exhibiting temperature-dependent sex determination. Climate change is also affecting nesting species indirectly, via range shifts into suboptimal nesting areas, reduced quality of nest-building environments, and changes in interactions with nest predators and parasites...
December 16, 2016: Biological Reviews of the Cambridge Philosophical Society
J L Reneker, S J Kamel
The most recent climate change projections show a global increase in temperatures, along with major adjustments to precipitation, throughout the 21st century. Species exhibiting temperature-dependent sex determination are highly susceptible to such changes since the incubation environment influences critical offspring characteristics such as survival and sex ratio. Here we show that the mean incubation duration of loggerhead sea turtle (Caretta caretta) nests from a high-density nesting beach on Bald Head Island, North Carolina, USA has decreased significantly over the past 25 yr...
December 2016: Ecology
Yuiko Matsumoto, Brette Hannigan, David Crews
The environment surrounding the embryos has a profound impact on the developmental process and phenotypic outcomes of the organism. In species with temperature-dependent sex determination, gonadal sex is determined by the incubation temperature of the eggs. A mechanistic link between temperature and transcriptional regulation of developmental genes, however, remains elusive. In this study, we examine the changes in DNA methylation and histone modification patterns of the aromatase (cyp19a1) gene in embryonic gonads of red-eared slider turtles (Trachemys scripta) subjected to a temperature shift during development...
2016: PloS One
Christopher J Butler, Brian D Stanila, John B Iverson, Paul A Stone, Matthew Bryson
Chelonians are expected to be negatively impacted by climate change due to limited vagility and temperature-dependent sex determination. However, few studies have examined how freshwater turtle distributions may shift under different climate change scenarios. We used a maximum entropy approach to model the distribution of five widespread North American Kinosternon species (K. baurii, K. flavescens, K. hirtipes, K. sonoriense, and K. subrubrum) under four climate change scenarios. We found that areas with suitable climatic conditions for K...
November 2016: Ecology and Evolution
M Oswaldo Tovar Bohórquez, Alejandro S Mechaly, Lily C Hughes, Daniela Campanella, Guillermo Ortí, Luis F Canosa, Gustavo M Somoza
In vertebrates, kisspeptins and their receptors are known to be related to puberty onset and gonadal maturation, however, there are few studies concerning their role in early development. Here, we characterize the kisspeptin system in the pejerrey, Odontesthes bonariensis, a fish with strong temperature-dependent sex determination. We reconstructed the phylogenetic history of the two ligands (kiss1 and kiss 2) and two receptors (kissr2 and kissr3) in pejerrey in the context of recent classifications of bony fishes, determined their tissue distribution and documented the early expression pattern of these ligands and receptors...
February 2017: Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
T J Mpofu, M M Ginindza, N A Siwendu, K A Nephawe, B J Mtileni
The study was conducted to determine the effect of agro-ecological zone, season of birth and sex on Nguni calves' pre-weaning performance. Production indices such as birth weight (BW), weaning weight (WW), pre-weaning average daily gain (P-ADG) and pre-weaning gain (P-WG) were assessed in the different agro-ecological zones. Herd records on performance of 826 Nguni calves' from nine Nguni herds representing different agro-ecological zones: arid zone (n = 217); semi-arid zone (n = 296); dry sub-humid zone (n = 118) and humid zone (n = 195) were used for the analysis of pre-weaning calf performance...
January 2017: Tropical Animal Health and Production
Bao-Jun Sun, Teng Li, Yi Mu, Jessica K McGlashan, Arthur Georges, Richard Shine, Wei-Guo Du
The adaptive significance of temperature-dependent sex determination (TSD) has attracted a great deal of research, but the underlying mechanisms by which temperature determines the sex of a developing embryo remain poorly understood. Here, we manipulated the level of a thyroid hormone (TH), triiodothyronine (T3), during embryonic development (by adding excess T3 to the eggs of the red-eared slider turtle Trachemys scripta, a reptile with TSD), to test two competing hypotheses on the proximate basis for TSD: the developmental rate hypothesis versus the hormone hypothesis Exogenous TH accelerated embryonic heart rate (and hence metabolic rate), developmental rate, and rates of early post-hatching growth...
October 26, 2016: Proceedings. Biological Sciences
Clare E Holleley, Stephen D Sarre, Denis O'Meally, Arthur Georges
Is sex a product of genes, the environment, or both? In this review, we describe the diversity of sex-determining mechanisms in reptiles, with a focus on systems that display gene-environment interactions. We summarise the field and laboratory-based evidence for the occurrence of environmental sex reversal in reptiles and ask whether this is a widespread evolutionary mechanism affecting the evolution of sex chromosomes and speciation in vertebrates. Sex determination systems exist across a continuum of genetic and environmental influences, blurring the lines between what was once considered a strict dichotomy between genetic sex determination and temperature-dependent sex determination...
2016: Sexual Development: Genetics, Molecular Biology, Evolution, Endocrinology, Embryology, and Pathology of Sex Determination and Differentiation
Michael Czerwinski, Anirudh Natarajan, Lindsey Barske, Loren L Looger, Blanche Capel
Temperature dependent sex determination (TSD) is the process by which the environmental temperature experienced during embryogenesis influences the sex of an organism, as in the red-eared slider turtle Trachemys scripta elegans. In accord with current paradigms of vertebrate sex determination, temperature is believed to exert its effects on sexual development in T. scripta entirely within the middle third of development, when the gonad is forming. However, whether temperature regulates the transcriptome in T...
December 1, 2016: Developmental Biology
Siat Yee Fong, Terrence Piva, Chaitali Dekiwadia, Sylvia Urban, Tien Huynh
BACKGROUND: Clinacanthus nutans (Burm. f.) Lindau leaves are widely used by cancer patients and the leaf extracts possess cytotoxic and antiproliferative effects on several human cancer cell lines. However, the effect of C. nutans leaf extract on human melanoma, which is the least common but most fatal form of skin cancer and one of the most common cancers diagnosed in both sexes worldwide, is unknown. There is also limited information on whether the bioactivity of extracts differs between C...
September 20, 2016: BMC Complementary and Alternative Medicine
Joanne Braun McNeill, Larisa Avens, April Goodman Hall, Lisa R Goshe, Craig A Harms, David W Owens
Alterations have occurred and continue to manifest in the Earth's biota as a result of climate change. Animals exhibiting temperature dependent sex determination (TSD), including sea turtles, are perhaps most vulnerable to a warming of the Earth as highly skewed sex ratios can result, potentially leading to population extinction resulting from decreased male recruitment. Recent studies have begun to quantify climate change impacts to sea turtle populations, especially in terms of predicting effects on hatchling sex ratios...
2016: PloS One
Mohannad Ismail, Margot Brooks
Adaptation to temperature changes is vital to reduce adverse effects on individuals, and some may present phenotypic changes, which might be accompanied with physiological costs in fitness traits. The objective of this study was to determine whether the two strains of the herbivore Eccritotarsus catarinensis, a biological control agent against water hyacinth in South Africa, differ in their responses to temperature according to their geographical origin. We experimentally quantified the responses of the two strains, at three constant temperatures: 20°C, 25°C and 30°C, using laboratory cultures that originated from Brazil and Peru, where climates differ...
August 2016: Journal of Thermal Biology
Christopher M Murray, Michael Easter, Sergio Padilla, Mahmood Sasa Marin, Craig Guyer
Spatial variation in global climate change makes population-specific responses to this enigmatic threat pertinent on a regional scale. Organisms with temperature-dependent sex determination (TSD) potentially possess a unique physiological susceptibility that threatens population viability if rapid environmental effects on sex ratios render populations non-viable. A heavily male-biased sex ratio for hatchling American crocodiles of the Tempisque Basin, Costa Rica requires assessment of how nest temperature affects sex determination at this site, how females might compensate for these effects when creating nests, and how current patterns of climate change might alter future sex ratios and survival in hatchling cohorts...
August 2016: Journal of Thermal Biology
Lindsey K Manshack, Caroline M Conard, Sarah A Johnson, Jorden M Alex, Sara J Bryan, Sharon L Deem, Dawn K Holliday, Mark R Ellersieck, Cheryl S Rosenfeld
Developmental exposure of turtles and other reptiles to endocrine disrupting chemicals (EDCs), including bisphenol A (BPA) and ethinyl estradiol (EE2, estrogen present in birth control pills), can induce partial to full gonadal sex-reversal in males. No prior studies have considered whether in ovo exposure to EDCs disrupts normal brain sexual differentiation. Yet, rodent model studies indicate early exposure to these chemicals disturbs sexually selected behavioral traits, including spatial navigational learning and memory...
September 2016: Hormones and Behavior
David Musiolek, Petr Kočárek
For ectothermic animals, selection of a suitable microhabitat is affected by a combination of abiotic and biotic factors. Also important is the trade-off between those microhabitats with optimal microclimatic conditions and food availability vs. those with the lowest level of competition and lowest risk of predation. Central European species of groundhoppers (Orthoptera: Tetrigidae) live in locations with small-scale mosaics of patches formed by bare ground, moss cushions and vascular plants (grasses and forbs)...
August 2016: Die Naturwissenschaften
Ilya G Kichigin, Massimo Giovannotti, Alex I Makunin, Bee L Ng, Marsel R Kabilov, Alexey E Tupikin, Vincenzo Caputo Barucchi, Andrea Splendiani, Paolo Ruggeri, Willem Rens, Patricia C M O'Brien, Malcolm A Ferguson-Smith, Alexander S Graphodatsky, Vladimir A Trifonov
Squamate reptiles show a striking diversity in modes of sex determination, including both genetic (XY or ZW) and temperature-dependent sex determination systems. The genomes of only a handful of species have been sequenced, analyzed and assembled including the genome of Anolis carolinensis. Despite a high genome coverage, only macrochromosomes of A. carolinensis were assembled whereas the content of most microchromosomes remained unclear. Most of the Anolis species have homomorphic XY sex chromosome system...
October 2016: Molecular Genetics and Genomics: MGG
Christopher M Murray, Michael Easter, Mark Merchant, Justin L Rheubert, Kelly A Wilson, Amos Cooper, Mary Mendonça, Thane Wibbels, Mahmood Sasa Marin, Craig Guyer
Effects of xenobiotics can be organizational, permanently affecting anatomy during embryonic development, and/or activational, influencing transitory actions during adulthood. The organizational influence of endocrine-disrupting contaminants (EDC's) produces a wide variety of reproductive abnormalities among vertebrates that exhibit temperature-dependent sex determination (TSD). Typically, such influences result in subsequent activational malfunction, some of which are beneficial in aquaculture. For example, 17-αmethyltestosterone (MT), a synthetic androgen, is utilized in tilapia farming to bias sex ratio towards males because they are more profitable...
September 15, 2016: General and Comparative Endocrinology
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