Recovery from heat‐induced infertility—A study of reproductive tissue responses and fitness consequences in male Drosophila melanogaster

Abstract

Temperature is a critical abiotic factor for many organisms and can turn into an environmental stressor, particularly for ectotherms. Elevated temperatures are known to affect an ectotherm's physiology, behavior, and, on a broader scale, its overall performance (Huey & Stevenson, 1979). When critical thermal limits are exceeded, both viability and reproductive potential are harmed (Sales et al., 2021). In recent years, most research assessing phenotypic effects under increasing temperatures has incorporated mainly

Fertility loss under thermal stress: males have lower fertility limits but no evidence of sex differences in sensitivity

“…In R. robini it is, therefore, likely that spermatogenesis is more susceptible to complete failure during thermal extremes compared to oogenesis. In other species thermal damage to sperm and testes has been demonstrated (Hurley et al 2018, Sales et al 2018, Canal Domenech and Fricke 2022 and we propose that a similar effect likely explains our results. It may be possible that the sex difference in TFL we have observed is a consequence of sexual body-size dimorphism in R. robini: males are roughly 30% smaller than females (Plesnar-Bielak et al 2013).…”

“…Whether individuals would fully regain fertility if given a longer recovery period remains unknown in this system, but it was previously shown that T. castaneum males only fully recovered fertility 20 days post heat stress (Sales et al 2021). However, there have been a mixture of results as to whether individuals can recover fertility loss in other species, and recovery may be due to differences between species, traits measured and length of recovery period (Sales et al 2021, Walsh et al 2021, Canal Domenech and Fricke 2022). Our results suggest that fertility loss due to heat stress may only be temporary and therefore the impact on population level fitness may be minimised if heatwaves remain infrequent.…”

“…Indeed, heat stress during different life stages has been shown to impact adult reproductive traits to varying degrees (Sales et al 2021, Walsh et al 2021). These negative effects of thermal stress on fertility appear to also have sex‐specific effects, especially among ectotherms, with the greatest negative effects often found among males (Sales et al 2018, 2021, Zwoinska et al 2020, Baur et al 2022), and are likely a consequence of testes and sperm being particularly sensitive to heat stress (Hurley et al 2018, Sales et al 2018, 2021, Canal Domenech and Fricke 2022). The pattern of male fertility loss being greatest compared to females during thermal stress is, however, not found in all cases (Santos et al 2023).…”

“…Because evidence is restricted to a limited number of examples, debate remains, and it is clear that a wider range of taxonomic groups are needed to determine the generalisation of these results (Iossa 2019, Walsh et al 2019b). Similarly, there are mixed findings as to whether individuals can recover from fertility loss (Parratt et al 2021, Sales et al 2021, Walsh et al 2021, Canal Domenech and Fricke 2022). For example, many Drosophila species males were found to suffer increased fertility loss over time, post heat stress (Parratt et al 2021), whereas Tribolium castaneum males regained thermally induced fertility loss when given a long enough recovery period (Sales et al 2021).…”

Heatwaves are detrimental to fertility in the viviparous tsetse fly

“…Abnormal ovaries were found in Glossina fuscipes fuscipes after exposure to constant 30°C [ 77 ]. Other studies have shown that infertility can be temporary in Drosophila melanogaster and T. castaneum , indicating that physiological repair can occur over time [ 38 , 78 ]. Periodic dissections in tsetse investigating oocyte production and release post heatwave exposure may elucidate the mechanism of this response.…”