5.3. Cryopreservation of semen
The maintenance of honey bee stocks currently requires costly and labour intensive annual propagation. Current threats to the biodiversity of honey bees, and the need to select lines tolerant to pests and diseases, creates a need to develop techniques for the cryopreservation of honey bee germplasm. Repositories would provide a resource for breeding purposes and the preservation and recovery of selected stocks and endangered populations.
High viability and motility of honey bee semen cryopreserved in liquid nitrogen and thawed has been demonstrated, although fertility is greatly reduced in the spermatheca of queens. Current techniques demonstrate that fertility is adequate to produce sequential generations of queens inseminated with frozen-thawed semen for breeding purposes, although they are not sufficient to head productive colonies (Hopkins et al., 2012). Further research is being conducted to perfect these techniques.
Current recommendations for cryopreservation:
- Cryoprotectants: dimethyl sulfoxide (DMSO) and ethylene glycol (see Wegener & Bienfeld, 2010 and Hopkins & Herr, 2010)
- Programmable freezing rate: 3ºC / min, from 4ºC to - 40ºC, then place samples in liquid nitrogen (see Hopkins et al., 2012).
- Thawing rate, 40ºC for 10 seconds (see Hopkins et al., 2012)