Proteomic differences in seminal fluid of social insects whose sperm differ in heat tolerance

Abstract

In the coming years, climate change is likely to increase the frequency and intensity of heatwaves. In many organisms, heat stress provokes physiological perturbations and can lead to decreased male fertility. Bumblebees are endo-heterothermic but display interspecific differences in thermotolerance that could have conservation implications. For the species of concern Bombus magnus , exposure to high temperatures can severely reduce sperm quality and, consequently, reproductive success. Such is not the case for B. terrestris , a ubiquitous species. To decipher the mechanisms at play, we characterized the seminal fluid proteomes of the two species. We quantified 1121 proteins, of which 522 were differentially expressed between B. terrestris and B. magnus . Several proteins with protective functions, such as proteases, antioxidant proteins and various heat-shock proteins, were present at higher levels in B. terrestris than in B. magnus under both control and heat-stress conditions . The same was true for proteins involved in cellular homeostasis, immunity, lipid/sugar metabolism and thermotolerance. Furthermore, proteins involved in the capture and elimination of reactive oxygen species also occurred at much high levels in B. terrestris . Overall, these results clearly indicate differences in the seminal proteome of the more thermotolerant B. terrestris versus B. magnus . The differences may contribute to explaining interspecific differences in sperm survival.

Experimental heatwaves reduce the effectiveness of ejaculates at occupying female reproductive tracts in a model insect

“…Third, exposure to higher temperatures may have partially reduced movement by affecting flagellar activity [27,88] and morphology [28]. Fourth, heat stress could denature and/or alter the expression of seminal fluid proteins, known to influence female behaviour related to sperm use [89][90][91]92]. Generally, the failure of heat-exposed male sperm to occupy the correct anterior bursal and spermathecal storage sites could render a greater proportion vulnerable to displacement by muscular contractions, ova migration and male intromissions [43,74,86].…”