No abstract

A honey bee (Apis mellifera Linnaeus; Hymenoptera: Apidae) queen’s life expectancy is strongly dependent on the number of sperm she obtains by mating with drones during nuptial flights. Unexplained replacement of queens by the colony and young queens showing sperm depletions have been reported in North America, and reduced drone fertility has been a suspected cause. The aim of this study was to evaluate drone reproductive qualities during the queen-rearing season, from May to August. Drones from two different genetic lines were reared six times during the 2012 beekeeping season at our research centre in Québec (Canada). Semen volume as well as sperm number and viability were assessed at the ages of 14, 21, and 35 days. Results showed (1) a greater proportion of older drones with semen at the tip of the genitalia after eversion; (2) an influence of rearing date on semen production; and (3) no influence of drone genetic line, age or time of breeding on sperm viability. These results highlight the necessity of better understanding drone rearing and how it can be improved to ensure optimum honey-bee queen mating.

The fertility and fecundity of the queen are vital to the success of a honey bee colony (Apis mellifera L.). Young mated queens are shipped worldwide to meet the demand of the beekeeping industry. Since little is known about the conditions experienced by queens in transit from breeders to beekeepers and the importance of these conditions on the queens' reproductive potential, we conducted a two-part study. First, queen shipments from the USA and Canada to Canadian beekeepers were monitored to measure thermal conditions during shipment. A total of 39 shipments were followed in 2017 and 2018. Monitoring revealed variable temperatures during shipment, with occasional periods of lows (10-15°C) and highs (30-36°C). Second, young mated queens were placed in different shipping boxes with or without attendant bees and exposed to one of three temperatures (6°C, 26°C, and 40°C) for 2 h. We then compared the thermoregulation within shipping boxes, and the viability of sperm in each queen's spermatheca. Our results show that both low and high temperatures significantly decrease sperm viability, and that the addition of loose attendant bees within shipment boxes helps maintain the temperature at 26°C when exposed to low temperature and delays the temperature increase when temperatures are high. The study shows the potential to improve current honey bee shipping methods in order to mitigate variable conditions experienced by bees during transportation.

Supplemental feeding of honey bee (Apis melliferaL., Hymenoptera: Apidae) colonies in spring is essential for colony buildup in northern apicultural regions. The impact of pollen and syrup feeding on drone production and sperm quality is not well-documented, but may improve fecundation of early-bred queens. We measured the impact of feeding sucrose syrup, and protein supplements to colonies in early spring in eastern Canada. Drones were reared under different nutritional regimes, and mature individuals were then assessed in regard to size, weight, and semen quality (semen volume, sperm count, and viability). Results showed significant increases in drone weight and abdomen size when colonies were fed sucrose and a protein supplement. Colonies receiving no additional nourishment had significantly less semen volume per drone and lower sperm viability. Our study demonstrates that feeding honey bee colonies in spring with sucrose syrup and a protein supplement is important to enhance drone reproductive quality. RÉSUMÉ: L'administration de suppléments alimentaires aux colonies de l'abeille domestique (Apis melliferaL., Hymenoptera: Apidae) au printemps est essentielle pour le bon développement des colonies dans les régions apicoles nordiques. L'impact de la supplémentation des colonies en pollen et en sirop sur la production des faux-bourdons et la qualité du sperme demeure peu documenté mais pourrait résulter en une meilleure fécondation des reines produites tôt en saison. Nous avons mesuré l'impact de la supplémentation en sirop et/ou en supplément de pollen sur les colonies d'abeilles tôt au printemps dans l'est du Canada. Les faux-bourdons ont été élevé sous différents régimes alimentaires et les individus matures ont ensuite été évalués pour leur taille, leur poids ainsi que la qualité de leur sperme (volume de sperme, nombre et viabilité des spermatozoïdes. Les résultats montrent une augmentation significative du poids et de la taille de l'abdomen des faux-bourdons élevés dans les colonies recevant des suppléments de sirop et de protéine. Les faux-bourdons élevés dans les colonies ne recevant aucun supplément alimentaire possédaient les plus petits volumes de sperme ainsi que la plus faible viabilité des spermatozoïdes. Notre étude démontre que la supplémentation alimentaire des colonies en sirop et en protéines au printemps est importante pour favoriser la qualité reproductive des faux-bourdons.

Preservation of honey bee (Apis mellifera L., Hymenoptera: Apidae) sperm, coupled with instrumental insemination, is an effective strategy to protect the species and their genetic diversity. Our overall objective is to develop a method of drone semen preservation; therefore, two experiments were conducted. Hypothesis 1 was that cryopreservation (-196 °C) of drone semen is more effective for long-term storage than at 16 °C. Our results show that after 1 yr of storage, frozen sperm viability was higher than at 16 °C, showing that cryopreservation is necessary to conserve semen. However, the cryoprotectant used for drone sperm freezing, dimethyl sulfoxide (DMSO), can harm the queen and reduce fertility after instrumental insemination. Hypothesis 2 was that centrifugation of cryopreserved semen to reduce DMSO prior to insemination optimize sperm quality. Our results indicate that centrifuging cryopreserved sperm to remove cryoprotectant does not affect queen survival, spermathecal sperm count, or sperm viability. Although these data do not indicate that centrifugation of frozen-thawed sperm improves queen health and fertility after instrumental insemination, we demonstrate that cryopreservation is achievable, and it is better for long-term sperm storage than above-freezing temperatures for duration of close to a year.