Importing frozen honey bee sperm is key to conservation
Honey bees are not native to North or South America, and importing into the U.S. has been tightly restricted since the 1920s. As a result, U.S. honey bees have limited genetic diversity.
Were importing germplasm from Old World populations around Europe to increase genetic diversity here, Hopkins said. The goal is to improve commercial breeding for bees so they can better fight off diseases and parasites.
Everything we do in this effort is to ensure bees survive to pollinate our food sources, he said.
Hopkins and other WSU entomologists have collected genetic material in Italy, Slovenia, the Republic of Georgia and Kazakhstan since they received a USDA permit to import honey bee semen in 2008.
WSU scientists also transport fresh sperm, but its shelf life is only about two weeks. Hopkins developed a method for freezing the material as part of his masters degree at Eastern Washington University, and he refined it further when he came to WSU to earn his Ph.D.
Cryogenic freezing has been used to preserve germplasm from animals like cattle for decades, he said. I adapted it for honey bees. Right now we are the only repository for bee germplasm in the world.
The importation process starts with a trip to collect material overseas. Once WSU scientists arrive in a country, they work with local beekeepers or government agencies equivalent to the USDA to visit a variety of hives.
They collect mature male bees, called drones, and then extract semen. Each male produces about one microliter. For comparison, a single drop of water is approximately 100 microliters.
We try to collect hundreds of microliters of sperm every day were there, so those are long days, Hopkins said.
The semen is frozen in the origin country because freezing fresh material yields the best results. A special substance is added to avoid damaging the cells during freezing. Once back at WSU, the samples are stored at -196C (-320F) in a tank of liquid nitrogen.
Theoretically, the sperm can stay viable at that temperature for 10,000 years or more, Hopkins said. It can then be thawed out and used to breed honey bees here.
Unfortunately, the breeding process is not as simple as inseminating one queen and then providing the second generation of bees to breeders. Second generation queens contain only 50 percent of the imported European DNA.
Image courtesy of wsu.edu