Preservation of honey bee spermatozoa using egg yolk and soybean lecithin-based semen extenders and a modified cryopreservation protocol

Abstract

Better protocols and suitable extenders for semen handling and cryopreservation are required for honey bees to enhance sperm quality and fertility similar to that of other species. The purpose of the present research is the improvement of honey bee sperm quality using different semen extenders and a modified cryopreservation protocol. Three different extenders were used: (1) buffer and egg yolk (EY); (2) buffer and 0.5% soybean lecithin (SL0.5); and (3) buffer and 2% soybean lecithin (SL2). Semen was collected and then diluted with the experimental extenders. The diluted semen was gradually cooled in a refrigerator to 5 °C and immediately loaded into straws and frozen with liquid nitrogen. Motility and viability data analyzed using the GENMOD and GLM procedure of SAS software. The results demonstrate that the mean fresh sperm motility in EY (4.75 ± 0.14) and SL2 (4.5 ± 0.2) were significantly (p < 0.05) higher than the SL0.5 (4.12 ± 0.12). Also, the mean of cooled motile spermatozoa in EY and SL2 were significantly higher than the SL0.5 (3.87 ± 0.24). Post-thawed sperm motility in EY (3.6 ± 0.24) was significantly (p < 0.05) higher than the other extenders. Furthermore, percentage of viable spermatozoa in EY (69.75 ± 2.32%) was significantly higher than SL0.5 and SL2 (38.5 ± 2.32 and 45 ± 2.32% respectively. Therefore, according to the results of this study, use of an egg yolk-based extender could better maintain honey bee semen motility and viability after freeze-thawing process, compared to SL-based extenders. However, more advanced tests and fertility evaluation are needed to reveal the exact effects of egg yolk and lecithin based semen extenders on post-thawed drone sperm quality.