When we think of reproduction, we normally think of a sperm and egg fusing and then dividing many times to produce offspring. But are virgin births possible where there is no male-derived sex cell involved?
The answer is yes. Scientists from the University of Sydney in Australia have discovered the gene that causes virgin birth in the Cape honeybee, a subspecies of honeybee native to South Africa.
But what is a virgin birth and how do they happen? By definition, a virgin birth is where a female can reproduce to produce offspring without the input of male sperm. In the case of the Cape honeybee, the female workers can lay eggs that develop into females asexually. Males aren’t involved as male worker bees of this subspecies are unable to mate. This process is given the name ‘Thelytokous parthenogenesis’.
How is this biologically possible and why does the Cape honeybee do it? In sexual reproduction 2 chromosome sets are required (one from the mother, one from the father), so how can Cape bees reproduce asexually? Studies from other model organisms have shown that a female can produce fertile eggs with the right number of chromosomes. (This is) either by fusing an egg cell with another or the egg progenitor can undergo a variant form of cell division that leaves the 2 sets of chromosomes required. Cape honeybees do this because virgin birth allows birth of a new Queen as this form of reproduction only happens when the old Queen dies. This ensures that the colony can survive.
The gene responsible for virgin birth was identified using modern genomic tools by behavioural geneticist Professor Benjamin Oldroyd and colleagues by comparing the genomes (genetic makeup) of the Cape honeybee to other subspecies. This allowed the discovery of the virgin birth gene, which was named GB45239, situated on chromosome 11. This was a very exciting time as scientists had been ‘looking’ for the gene for 30 years! It can provide insights into the origin of sexual reproduction and the origin of animal societies/hierarchies. Also, it raises the possibility of a genetic ‘switch’, meaning that the virgin birth gene can be ‘turned off’ in pests, which has implications in agriculture, biotechnology, and many other fields.
However, the presence of virgin birth can cause many issues. In principle, any female worker bee can be genetically ‘reincarnated’ as the next Queen. This, as you can imagine, creates a lot of competition, not common in a cooperative ecological society. This ultimately leads to societal parasitism, when workers invade foreign colonies and persuade the host to feed their own larvae, eventually causing death of the foreign colony. In fact, approximately 100,000 colonies die each year due to societal parasitism, a reason why Prof Oldroyd says that we “must keep these bees out of Australia”.
The advantages and disadvantages of virgin birth are conflicting, and it is unclear as to what would happen if Cape honeybees were introduced into other countries. Would they increase biodiversity or have devastating impacts on the food and agriculture industry? More research is being done to investigate this, so hopefully we’ll have a clearer answer soon as to the effects on the ecosystems around us.