Sperm storage and artificial insemination have been studied largely, since 1970, for the preservation of mammals, but also for bees, in danger of extinction.
Climate change, overexploitation of land, the introduction of invasive species, and several other factors have caused the imbalance of natural ecosystems and the disappearance of about half of animal and plant species in 40 years.
Nowadays, a large part of animal biodiversity presents a risk of population loss or extinction. In addition to the rich heritage represented by biodiversity, it is an important economic driver, particularly for agriculture, so the preservation of biodiversity is a great motivation for research.
The little biting creatures, bees, are the subject of the plan of great concern to scientists because of their vital role in turning the wheels of international trade from agriculture to fashion through the process of pollination.
Estimates of global agricultural income from this species are $ 265 billion as it is responsible for 75% of the production of fruits, vegetables and seeds.
The winter loss in recent years of bee populations has averaged 20% in Europe, and has reached 53% in some countries. This loss is caused mainly by global warming, the use of pesticides, monoculture and exposure to new viruses and pathogens. This represents a catastrophe and not just a crisis that endangers humanitarian existence.
The preservation of bees then became an emergency and several efforts are being made to this end, including the ban on pesticides. But protecting these pollinators required more effort because the causes of their mortality are diverse.
Preserving bees sperm
Since the 1970s, several studies have been carried out on the possibility of conservation of bee sperm and artificial insemination with the aim of preserving the species.
Sperm conservation could become a powerful tool, even essential, for the selection of rare characters, such as resistance against Varroa and to increase the capacity in mating and in eggs by maintaining the alleles of the most powerful queens.
Semen can be stored for long periods. Even at ambient conditions, it stays alive and does not lose its fertility for several weeks. However, long-term storage frequently causes genetic damage during the freezing stage. It mainly affects the concentration, motility and viability of spermatozoa and ultimately increases the risk of inbreeding. Factors affecting the success of the freezing stage include toxicity of cryoprotectants, freezing speed and cold shock.
Researchers have also proposed adding a different genome to the target colony by storing sperm from other colonies. But, artificial insemination with short-term stored sperm remains more reliable. This makes the success rate of this operation lower in bees than in mammals.
Dilution and long-term storage of bees sperm
The semen is first diluted properly. Sodium, potassium, calcium and magnesium ions are essential for maintaining sperm motility and vitality. Hence it is required at the dilution stage.
Then, it is sealed with air on both sides in a pipette. It is then cooled to + 4 °C for 2 hours to avoid a cold shock. It should be cooled to -40 °C while decreasing by 3 ° C / min, and finally transported in liquid nitrogen at -196 ° C.
When reused, it is dissolved for 30 s at + 37 ° C.
Bees artificial insemination process
After collection and storage of the sperm, the queen of the target colony is anesthetized with CO2 to prevent it from moving during insemination, and is then fixed in the appropriate position into the insemination tube.
The vagina emerges using a special pair of hooks. The injector end of the artificial insemination device is gently directed towards the vaginal opening, and 8 to 12 µL of semen are therefore transplanted.