Short-term storage at 16ºC of semen from Africanized honeybee drones using different extenders

Abstract

We evaluated the effect of different diluents on the preservation of cooled semen from Africanized bees at 16 °C, as a tool to enable its storage and transportation. Semen pools of 50 drones from 10 different colonies were obtained by the endophallus eversion technique. The pools were then divided into four aliquots that were diluted in Tris, Tris + yolk (EY), Collins or Ringer, in a ratio of 12:1 (diluent:semen). The samples were cooled in a biological incubator at 16 °C and evaluated for pH, motility, viability, membrane functionality and sperm morphology at 0, 24, 72 and 96 h. Ringer's extender promoted total loss of sperm motility at 24 h, while at 96 h, the highest motility values (P < 0.05) were exhibited by Tris + EY extender (25 ± 4.2%), compared to Tris (11.4 ± 2.8%) and Collins (2.6 ± 0.9%). After 96 h, the viability of samples diluted in Ringer's extender (34.4 ± 8.6%) showed a pronounced decrease compared to Tris (73.3 ± 6.8%). For sperm membrane functionality, both Tris and Ringer's extender were able to maintain values greater than 45% of functional membranes up to 96 h. For sperm morphology, Tris extender provided the highest values for normal sperm over time, especially compared to Ringer's extender (P < 0.05). In conclusion, we point out that Tris-based extenders, with or without egg yolk, are the most suitable for use in short-term storage at 16 °C of Africanized honeybee drone spermatozoa for up to 96 h.