The effect of mixed honeybee drone semen on sperm quality characteristics: A preliminary study

Abstract

Following copulation, sperm of multiple honeybee (Apis mellifera (A.m.) Linnaeus (Apidae)) drones are mixed inside the spermatheca of a queen, and sperm behaviour in this environment is of importance for sperm survival and successful fertilization. The polyandrous mating system of honeybees further may allow for cryptic female choice and sperm competition to select for specific sperm traits to enable successful reproduction. This preliminary study therefore examined multiple sperm quality parameters in mixed drone semen. Thirty-one drone ejaculates were collected and split to be mixed with one and two other drones’ semen. A computerised sperm analysis system was used for analysing sperm functionality parameters, at baseline and 60 minutes. Morphology measurements included head, tail, and total sperm length. Sperm concentration was significantly higher in three-drone samples compared to other groups (p < 0.001), while comparisons of sperm functional and morphometric parameters did not reveal differences. However, after 60 minutes, mixed semen samples displayed changes in terms of sperm functionality. The motility percentage significantly decreased in two-drone samples (p = 0.004). In contrast, three-drone samples had consistently lower motility and kinematic parameters at baseline, but following an hour it was the only group to show improvement in sperm progressive motility, swimming speed, and kinematics. Sperm concentration correlated with the majority of functionality parameters, while, morphological measurements did not. Sperm functionality changes observed in this study, can be attributed to a combination of factors, including, mixing of drone semen, sperm concentration, and time allowing for potential sperm interaction.