Short-term heat waves have long-term consequences for parents and offspring in stickleback

Extreme temperature events, such as heat waves, can have lasting effects on the behavior, physiology, and reproductive success of organisms. Here we examine the impact of short-term exposure to a simulated heat wave on condition, parental care, and reproductive success in a population of threespine stickleback (Gasterosteus aculeatus), a small fish with exclusive paternal care, currently experiencing regular heat waves. Males were either exposed to a simulated heat wave (23°C) for five days or held at an ideal temperature (18°C). All males had offspring that were raised at 18°C. We found that while mass and body condition were unaffected in males exposed to a heat wave, cortisol responses were dampened across the nesting cycle compared to control males. In addition, heat wave males had longer latency for eggs to hatch, lower hatching success, and were unable to parent at the same level as control males. Offspring of heat wave males had lower body condition, affecting swimming performance. Altogether, our results highlight the long-term impact that even short-term events can have on reproductive success, parental behavior, and subsequent generations, providing insight into population responses to rapid environmental change.

Methods
This code analyzes data from male stickleback pre- and post-heat wave exposure. Males assigned to the control group were placed in individual tanks at 18°C for five days. Males in the heat group were placed in individual tanks at 23°C for five days. All males were then transferred to new individual tanks at 18°C and measured for time to build a nest, hatching success, and paternal care behaviors.

This code analyzes mass and length data from male stickleback pre-heat wave exposure (pre-treatment), post-heat wave exposure (post-treatment), and post-parenting. Males assigned to the control group had mass measured five days post-initial measurement.

Additionally, this code analyzes cortisol from water. Cortisol was collected pre-treatment, post-treatment, and post-parenting. Males assigned to the control group had cortisol collected five days post-initial measurement.

Finally, this code analyzes life-history traits such as days to build a nest, latency to hatch, and percent hatching success for control and heat wave males.

In offspring, this code analyzes juvenile offspring length, mass, body condition, and behavior in a scototaxis assay.