Stored sperm differs from ejaculated sperm by proteome alterations associated with energy metabolism in the honeybeeApis mellifera

Abstract

Sperm are exposed to substantially different environments during their life history, such as seminal fluid or the female sexual tract, but remarkably little information is currently available about whether and how much sperm composition and function alters in these different environments. Here, we used the honeybee Apis mellifera and quantified differences in the abundance and activity of sperm proteins sampled either from ejaculates or from the female’s sperm storage organ. We find that stored and ejaculated sperm contain the same set of proteins but that the abundance of specific proteins differed substantially between ejaculated and stored sperm. Most proteins with a significant change in abundance are related to sperm energy metabolism. Enzymatic assays performed for a subset of these proteins indicate that specific protein activities differ between stored and ejaculated sperm and are typically higher in ejaculated compared to stored sperm. We provide evidence that the cellular machinery of sperm is plastic and differs between sperm within the ejaculate and within the female’s storage organ. Future work will be required to test whether these changes are a consequence of active adaptation or sperm senescence and whether they alter sperm performance indifferent chemical environments or impact on the cost of sperm storage by the female.However, these changes can be expected to influence sperm performance and therefore determine sperm viability or sperm competitiveness for storage or egg fertilization.

Females become infertile as the stored sperm's oxygen radicals increase

“…Here we additionally showed that if both parameters return to male levels, females suffer infertility. While in some species, the antioxidant pathway of sperm protection has demonstrated fitness benefits for males and females2728, antioxidants only have small effects on human fertility25. It is, therefore, possible that the other fundamental pathway of oxidative stress prevention (the one confirmed here) - a suppression of the formation of oxygen radicals (and other reactive oxygen species) - is important.…”

“…consider how antioxidants capture the oxygen radicals produced by the cell782127. The effectiveness of the antioxidant pathway in improving sperm performance is currently debated252728. The second pathway concerns the extracellular (i.e.…”

Drone exposure to the systemic insecticide Fipronil indirectly impairs queen reproductive potential

“…Thus, we hypothesize that the reduced quantity of spermatozoa recovered from the spermatheca of queens inseminated with semen from exposed drones could be also explained, independently of the phenomenon described above, by putative negative effects of such metabolic disruptions on the ability of spermatozoa to migrate. Similarly, we hypothesize that the higher mortality rate of spermatozoa observed in the spermatheca could be explained either by an impairment in the adaptation of spermatozoa having reached the spermatheca to the spermathecal fluid, which is necessary for long-term storage58, or by an increase of the mortality dynamic of the stored spermatozoa, which is a phenomenon that occurs naturally in the spermatheca over the time59.…”

Insights into the molecular basis of long-term storage and survival of sperm in the honeybee (Apis mellifera)

“…Previous studies indicate that biochemical pathways linked to energy metabolism are key contributors to the specific sperm traits reported in most social insects1617. For example, proteins involved in glycolysis are significantly enriched in honeybee sperm compared with sperm of fruit flies or humans18.…”