By Susan Milius
A new peek at the genetics of beetle genitals reveals the underpinnings of a battle of the sexes.
When mating, males of Japan’s flightless Carabus beetles insert a chitin-covered appendage that, once inside a female, pops out a plump sperm-delivery tube as well as a side projection called a copulatory piece. That piece doesn’t deliver any sperm, but steadies the alignment by fitting just so into a special pocket inside the female reproductive tract.
Researchers in Japan have now identified several regions of DNA that include genes controlling the length and width of the piece and pocket. Instead of being controlled mostly by the same genes, the beetles seem to have a fair amount of genetic freedom in changing one sex’s doodad dimensions without also resizing the other sex’s counterpart, evolutionary ecologist Teiji Sota of Kyoto University and colleagues say June 26 in Science Advances.