Responsiveness to cold snaps by turtle embryos depends on exposure timing and duration

Area of Science:

• Environmental Science
• Developmental Biology
• Climate Change Biology

Background:

• Transient temperature fluctuations, like heat waves and cold snaps, significantly impact organismal development and susceptibility to climate change.
• Previous research on the freshwater turtle, *Trachemys scripta*, focused on heat wave effects on genes for female hatchling production.
• The impact of cold snap timing and duration on male hatchling production and gonadal development remains understudied.

Purpose of the Study:

• To investigate how cold snap timing influences gonadal gene expression in *Trachemys scripta* embryos.
• To determine how the duration of an early cold snap affects resulting hatchling sex ratios in this species.

Main Methods:

• Exposure of *Trachemys scripta* embryos to transient cold snaps at different developmental stages.
• Analysis of gonadal gene expression patterns in response to cold snap timing.
• Monitoring of hatchling sex ratios following varying durations of early cold snap exposure.

Main Results:

• Gene responsiveness to cold temperatures changes dynamically across embryonic development.
• Genes responding to cold on incubation day 14 showed different expression patterns when exposed 4-8 days later.
• Extended cold snap exposure (>20 days) was required for testis development, suggesting baseline warm temperatures may reduce cold sensitivity.

Conclusions:

• Embryonic response to incubation temperature is highly sensitive to timing and duration, with rapid shifts in developmental pathways.
• Cold snap exposure timing and duration critically influence sex determination in *Trachemys scripta*.
• Understanding developmental plasticity is crucial for predicting species' responses to climate change.