Why the viability of spermatozoa diminishes in the honeybee (Apis mellifera) within short time during natural mating and preparation for instrumental insemination

Abstract

The viability of spermatozoa is a crucial parameter to appreciate semen quality and insemination potential of males both in natural mating and instrumental insemination. Here, we conducted a step-by-step investigation to address the questions why and at which step(s) the viability loss is occurring in spermatozoa of honeybees during natural mating and preparation for instrumental insemination. We detected the viability of spermatozoa in semen samples obtained from seminal vesicles and partly and fully everted endophalli of drones and in ejaculates collected into syringe tips, as well as the viability of spermatozoa in lateral oviducts of queens returning from the mating flight. A great diminish of spermatozoa viability (~10 %) was found in lateral oviducts of queens returning from mating flight (88.7 %) in comparison to viable spermatozoa in intact seminal vesicles of drones (98.1 %). Our results demonstrated that the decrease in spermatozoa viability occurs during the second stage of eversion of endophallus (viability loss, 3.3 %), and during injection of semen into the lateral oviducts of queens (viability loss, 6.1 %). The acting factor decreasing the viability of spermatozoa was the increased pressure occurring during the process of natural and instrumental insemination.