The study, published in the journal Discover Conservation, monitored seven olive ridley nests during the 2020–2021 nesting season, which runs from September through January in Ghana. Researchers led by Baidoo Abigail, Addo Samuel, and Agyekumhene Andrews deployed miniature HOBO U22 temperature data loggers directly into egg clutches as females were laying, positioning the devices near the center of the clutch where metabolic heat accumulates most. A second logger was buried roughly two meters from each nest at identical depth, acting as a control that recorded the background temperature of the surrounding beach sand. Both loggers recorded measurements every fifteen minutes for the entire incubation period, generating an unusually high-resolution record of the thermal environment experienced by developing embryos.

The most striking result concerns the moment when nest and sand temperatures part ways. For the first nineteen days of incubation, temperatures inside the eggs and in the adjacent sand tracked each other closely, with no statistically significant difference between them. But from day twenty onward—the period that coincides with the thermosensitive window during which hatchling sex is determined—nest temperatures rose consistently above sand temperatures and stayed elevated until the hatchlings emerged. The researchers attribute this divergence to metabolic heating: as embryos grow, their collective metabolic activity generates heat that warms the clutch from within, a phenomenon well documented in sea turtles but never before quantified at this West African site.

The numbers reveal how warm this rookery already runs. Mean nest temperatures across the seven nests ranged from 30.7 to 33.3 degrees Celsius, averaging 32.4 degrees, while adjacent sand temperatures averaged a cooler 31.7 degrees. When nest and sand temperatures diverged, the difference typically spanned 0.3 to 1.7 degrees Celsius, averaging about 0.9 degrees. These figures matter enormously because olive ridley turtles exhibit temperature-dependent sex determination: pivotal temperatures that produce equal numbers of males and females have been reported near 30.0 to 30.5 degrees Celsius, with anything warmer producing females. Since mean nest temperatures during the middle third of incubation—the critical sex-determining window—ranged from 31.5 to 32.9 degrees, the researchers conclude that the monitored nests exceeded pivotal thresholds for a substantial portion of development, strongly implying a female-biased hatchling output. Although sex ratios were not measured directly, the thermal signature alone is telling.

Temperature exerted its clearest influence on the pace of development. Incubation duration ranged from 45 to 57 days across the seven nests, averaging about 48 days, and was strongly and negatively correlated with mean nest temperature, with a correlation coefficient of minus 0.88. Warmer nests hatched markedly sooner, and mean nest temperature explained roughly 78 percent of the variation in incubation duration among nests. This relationship is among the most robust in reptilian developmental biology, but its confirmation in Ghanaian sands underscores how powerfully thermal conditions govern the timeline from egg to emergence, even across a modest sample of nests.

Perhaps surprisingly, temperature told a much weaker story about reproductive success itself. Hatching success ranged widely, from 53.4 to 95.5 percent, with a mean of 81 percent, and emergence success ranged from 44.3 to 92.9 percent, averaging 75.2 percent. Yet neither measure showed a meaningful correlation with mean nest temperature, and incubation duration likewise bore no relationship to success rates. The authors interpret this variability as evidence that factors beyond temperature—sand moisture, gas exchange within the nest chamber, beach compaction, and disturbance—interact in complex ways to determine whether embryos survive. The finding is a caution against attributing nest outcomes to temperature alone, particularly in natural environments where multiple stressors overlap.

The hatchlings themselves offered additional clues about thermal stress. Morphological abnormalities, most frequently non-uniform carapace development, were observed in hatchlings from nests with mean temperatures ranging from 32.6 to 33.2 degrees Celsius, and the two hottest nests, averaging 33.0 and 33.2 degrees, produced the greatest number of anomalies. Locomotor performance, assessed through a self-righting test in which hatchlings were placed upside down on moist sand and timed as they flipped themselves upright, showed a moderate association with nest temperature, though the relationship did not reach statistical significance in the small sample. Such performance traits are closely linked to post-emergence survival, since hatchlings that cannot right themselves or crawl quickly are more vulnerable to predators on their frantic dash to the sea.

The study also carries practical implications for how scientists model the future of sea turtle populations under climate change. Many recent studies estimate nest temperatures from sand temperature data by adding a correction—typically 0.5 to 1.0 degrees Celsius—to account for metabolic heating. The Ghanaian measurements, showing an average nest-to-sand difference of about 0.9 degrees during divergence, provide direct empirical support for the magnitude of such corrections at a tropical site where incubation temperatures already press against pivotal thresholds. The researchers note that the beach at Songor was artificially nourished in 2010 as part of coastal erosion mitigation, a process known elsewhere to alter sand thermal properties, though sediment characteristics were beyond the scope of this study. With global climate change projected to raise sand temperatures further, and with local coastal development reshaping nesting microclimates, accurate in-nest measurements will become ever more critical for forecasting sex ratios and hatchling survival.

The work is not without limitations. Seven nests constitute a small sample, spanning a single nesting season, and the statistical power to detect subtle relationships was correspondingly limited; tendencies toward cooler deeper nests and warmer larger clutches matched published patterns but did not reach significance. Fine-scale thermal gradients within clutches were not assessed, and hatchling sex was never directly determined. Still, as the authors emphasize, this study delivers the first baseline characterization of olive ridley nest thermal dynamics anywhere in West Africa, filling a conspicuous geographic gap in global sea turtle science. As temperatures continue to climb at nesting beaches worldwide, understanding precisely what developing embryos experience inside their eggs—not just what the surrounding sand feels like—may prove decisive for conserving one of the ocean’s most vulnerable travelers, and for ensuring that Ghana’s beaches keep producing hatchlings capable of completing their ancient journey back to the sea.

Subject of Research: Effects of incubation temperature on olive ridley sea turtle nest success and hatchling development at the Songor Ramsar Site, Ghana

Article Title: Effects of incubation temperature on olive ridley sea turtle nest success at the Songor Ramsar Site, Ghana

Article References: Abigail, B., Samuel, A., & Andrews, A. (2026). Effects of incubation temperature on olive ridley sea turtle nest success at the Songor Ramsar Site, Ghana. Discover Conservation, 3(1), Article 40. https://doi.org/10.1007/s44353-026-00109-8

Image Credits: AI Generated

DOI: 10.1007/s44353-026-00109-8

Keywords: olive ridley sea turtle, incubation temperature, metabolic heating, temperature-dependent sex determination, hatching success, Songor Ramsar Site, Ghana, climate change, nest temperature, hatchling performance, West Africa, conservation

The leopard gecko serves as an exemplary model for investigating TSD because its sex ratio can be predictably skewed by incubation temperature: cooler settings around 26.5°C yield exclusively females, whereas warmer environments near 31.5°C predominantly produce males. This clear dichotomy presented an ideal system for Miyagawa’s team to decipher the temporal and molecular dynamics that govern sexual fate in reptiles. Their research, poised to be published in Developmental Biology, employs a rigorous combination of histological examination and transcriptome-wide gene expression profiling to map how temperature steers gonadal development.

By incubating leopard gecko eggs at both female- and male-producing temperatures, and orchestrating controlled temperature shifts during key embryonic stages, the researchers delineated a defined temperature-sensitive period terminating at embryonic stage 36. Prior to this juncture, temperature transitions could reverse the sex trajectory, but beyond it, sex became irreversibly fixed. This critical finding finely demarcates the developmental window during which environmental cues exert their transformative influence on gonadal fate, expanding our understanding of the plasticity and constraints inherent in TSD systems.

Intriguingly, morphological differentiation between male and female embryos emerged only after initial molecular divergences had already taken place. Both temperature groups’ embryos were morphologically indistinguishable early on, indicating that gene expression shifts precede overt anatomical features. At the genetic level, the male development pathway was marked by the upregulation of genes such as AMH (Anti-Müllerian Hormone), DMRT1 (Doublesex and Mab-3 Related Transcription Factor 1), and SOX9, all pivotal regulators promoting testes formation. Conversely, female pathways showcased enhanced activity in genes like FOXL2 and CYP19A1, integral to ovarian differentiation. These gene expression patterns anticipate and drive the subsequent gonadal remodeling.

Beyond confirming well-characterized sex-determining genes, the study unveiled lineage-specific molecular nuances that challenge generalized paradigms. Notably, KDM6B, a gene previously implicated as a critical mediator in turtle male determination, displayed a distinct regulatory trajectory in the leopard gecko. Such divergence hints at evolutionary flexibility within the TSD framework, suggesting that while core genetic players may be conserved across reptiles, their temperature-sensitivity and hierarchical influence can evolve differentially across taxa. This nuance underscores the complex interplay of genetics and environment shaping vertebrate sex determination.

Furthermore, the research underscored the early activation of temperature-responsive genes related to RNA splicing and cellular adhesion dynamics, processes not traditionally associated directly with sex determination. This intimates that molecular responses to temperature begin at deeper, perhaps epigenetic or post-transcriptional, regulatory levels well before sex differentiation manifests physically. The involvement of such cellular machinery broadens the conceptual landscape of TSD, pointing to sophisticated networks through which thermal cues modulate gene expression.

The experimental approach also illuminated the deterministic effect of incubation temperature on sex ratios. Incubation at female-preferred temperatures consistently yielded exclusively female hatchlings, while male-favoring temperatures produced a predominantly male cohort but with a small proportion of females. This quantitative sex ratio control is emblematic of the leopard gecko’s tightly regulated TSD mechanism and serves as a robust benchmark for future ecological and molecular studies dissecting environmental sex determination in fluctuating habitats.

Importantly, Miyagawa and colleagues acknowledge the potential influence of maternal effects, including the thermal conditions experienced by gravid females and consequent egg maternal provisioning, which may modulate embryonic developmental trajectories and sex outcomes. Variability between experimental laboratories further highlights the importance of considering both intrinsic and extrinsic factors that converge to fine-tune TSD mechanisms. These complexities reveal that TSD is not only a product of incubation temperature but integrates broader ecological and physiological contexts.

This pioneering study fills a crucial phylogenetic void in TSD research, expanding molecular insights from turtles and crocodilians into squamate lizards. By linking transcriptomic changes to developmental stages within a well-characterized temporal framework, it provides a comprehensive map of how environmental cues are transduced into genetic programs that delineate sexual phenotype. Such integrative perspectives are indispensable for understanding the evolutionary plasticity that enables reptiles to adapt sex determination strategies to diverse ecological niches.

Moreover, the findings offer valuable implications for conservation biology, especially as global climate change exerts unprecedented impacts on habitat temperatures. Species with TSD systems, including the leopard gecko, may face skewed sex ratios under rising temperatures, threatening population viability. Understanding the molecular underpinnings and temporal sensitivity of TSD equips researchers and conservationists with predictive tools to monitor and perhaps mitigate these impacts through targeted interventions.

Professor Miyagawa reflects on the broader significance: “Our research not only unravels the intricate molecular choreography of temperature-induced sex determination in leopard geckos but also opens pathways to explore how environmental factors direct biological fate at the genomic and epigenetic levels across vertebrates.” Such insights transcend herpetology, contributing fundamentally to developmental biology, evolutionary theory, and environmental sciences.

Looking ahead, continued investigations building on these transcriptomic foundations are expected to clarify the downstream signaling cascades, epigenetic modifications, and potential feedback loops involved in TSD. The distinct regulatory patterns observed suggest species-specific adaptations worthy of detailed mechanistic exploration. Moreover, integrating physiological studies on maternal contributions and ecological variability will deepen our holistic understanding of how reptiles navigate the interplay between genes, environment, and development.

This landmark study, supported by Japan Society for the Promotion of Science grants and embraced by an interdisciplinary research ethos at Tokyo University of Science, exemplifies the power of combining developmental biology, genomics, and environmental physiology. As it unpacks the temperature-sex nexus with exquisite detail, it stands to influence a wide array of scientific fields and spark renewed interest in the molecular biology of TSD across vertebrates.

Subject of Research: Animals
Article Title: Gonadal development and gene expression in the leopard gecko during temperature-dependent sex determination
News Publication Date: 1-May-2026
References: DOI: 10.1016/j.ydbio.2026.02.011
Image Credits: Professor Shinichi Miyagawa from Tokyo University of Science, Japan
Keywords: Developmental biology, Genetics, Gene expression, Evolutionary biology, Animals, Temperature