Instrumental insemination of Apis mellifera, queens with hetero- and conspecific spermatozoa results in different sperm survival

Queens of Apis mellifera were inseminated each with 8 million spermatozoa of 4 different Apis species. To collect 8 million spermatozoa the following were needed: 1 A. mellifera drone; 8 A. cerana drones; 5 A. dorsata drones and 20 A. florea drones. Spermatozoa were obtained from vesiculae seminales and reconcentrated by centrifugation (1,000 g for 10 min). Compared to conspecific spermatozoa in the spermatheca, it was found: A. cerana spermatozoa entered in higher numbers and A. dorsata spermatozoa entered the spermatheca in lower numbers while A. florea spermatozoa reached a similar level. Three days and four weeks after insemination, the motility of spermatozoa in the spermatheca was determined. There was no significant difference in motility between conspecific A. mellifera spermatozoa and A. cerana spermatozoa. Further, the motility of spermatozoa of A. mellifera and A. cerana did not change within a period of 4 weeks. The decrease in motility of A. dorsata spermatozoa was significant after 3 days and 4 weeks. Also, the motility of spermatozoa of A. florea decreased significantly after 3 days and further after 4 weeks. All queens started oviposition 6 to 13 days after insemination. A. mellifera spermatozoa fertilize 57 percent of A. mellifera eggs (worker offspring) due to the low amount of spermatozoa in spermatheca. Fertilized eggs from queens inseminated with heterospecific spermatozoa did not develop. Based on the non-hatching rate of eggs, it is suggested that about 40 percent of A. mellifera eggs were fertilized by a. cerana and A. florea spermatozoa, but only few A. dorsata spermatozoa were able to fertilize because of the early loss of motility. Thus, only drone offspring emerged from the brood of A. mellifera queens inseminated with spermatozoa from A. cerana, A. dorsata and A. florea. The results demonstrate that transfer into the spermatheca depends mainly on the queen and is independent of the species of spermatozoa. The physiological conditions of the spermatheca result in different survival rates, which supports the idea of the significance of spermathecal fluid for sperm storage.