Morphological characterization of spermatozoa in <i>Apis mellifera</i> and the effect of processing and semen storage

The aim of this study was to establish a standardized approach for evaluating sperm morphology in the honey bee and to investigate the impact of processing techniques and semen storage on the incidence of sperm morphoanomalies. The first experiment was designed to characterize the sperm morphoanomalies in unaltered honey bee semen, examining if they are compatible with sperm motility and viability and determining their occurrence in the ejaculates of mature and healthy honey bee drones. The different forms of sperm morphoanomalies were described in detail. In the morphological analysis of fresh drone ejaculates, 7.77% of spermatozoa showed abnormal morphology on average, with 2.20%, 4.75% and 0.81% of head, tail and multiple defects, respectively. The method also allowed us to determine the status of acrosome integrity. The second experiment was designed to assess the impact of smearing and air-drying on the occurrence of sperm morphoanomalies, showing a significant increase in the incidence of both head and tail sperm defects when comparing to wet samples. In the third and fourth experiments, the effect of semen storage at room temperature and semen cryopreservation, respectively, on the occurrence of sperm morphoanomalies were investigated. The preservation of semen at 22 °C led to a significant increase in spermatozoa with coiled tails after day 1, whereas the remaining anomalies did not exhibit significant variations over time. The freezing-thawing process showed a more pronounced effect on the incidence of morphological defects, with an increase in the percentage of spermatozoa with deformed heads and coiled tails.