Assessing the resilience of sea turtle embryos to extreme temperatures

[Truncated] The survival and viability of sea turtle embryos is dependent upon favourable nest temperatures throughout the incubation period. Consequently, future generations of sea turtles may be at risk from increasing nest temperatures due to climate change, but little is known about how developing embryos will respond to thermal stress. Heat shock genes are likely to play an important role in resilience because they code for proteins that prevent cellular damage in response to environmental stressors. The experiments presented in this thesis provide the first evidence of sea turtle embryos using molecular mechanisms to mitigate the effects of acute thermal stress.

Sea turtle embryos (loggerhead, Caretta caretta and flatback, Natator depressus) were exposed to realistic and near-lethal temperatures of 36 °C for 3 hours. I investigated expression changes in the genes that code for heat shock proteins (hsps). Increased levels of expression of hsp60, hsp70, and hsp90 mRNA in heart tissue were measured in response to a brief heat stress, and it was determined that both hsp70 and hsp90 were useful biomarkers for assessing heat stress in the late-stage embryos of sea turtles. This method can be used as a platform to investigate variation in the thermotolerance response from the clutch to population scale, which can help anticipate the resilience of reptile embryos to extreme heating events.