Survival of honey bee (Hymenoptera: Apidae) spermatozoa stored at above-freezing temperatures

The development of practical techniques for the storage of honey bee, Apis mellifera L., semen would significantly improve our ability to breed for desirable genotypes and maintain genetic diversity in populations. Artificial insemination of queens has been possible for some time, but the semen used is usually freshly collected, or held for < 1 wk at room temperature. I examined the limitations of spermatozoal survival at nonfrozen temperatures. Pooled, diluted semen was stored in sealed capillary tubes at room temperature (25 degrees C) or in a refrigerator set to 12 degrees C, for periods up to 1 yr. Survival of spermatozoa was assayed by a dual fluorescent staining technique using SYBR-14 and propidium iodide stains, which readily distinguishes live and dead cells. No significant loss of viable spermatozoa occurred within the first 6 wk. Between weeks 6 and 9, the percent live spermatozoa fell from 80 to 58%, and remained at that level until after 39 wk. By week 52, samples at room temperature, but not at 12 degrees C, fell to 18.9% live spermatozoa. Nonfrozen storage of honey bee semen has potential for short-term preservation of germplasm, however several factors need to be studied further to optimize survival rates.