New research has shed light on the genetic basis behind the male redback spider's "self-sacrificial somersault" during mating, a behaviour that appears to invite cannibalism by the female.
During copulation, the male redback transfers sperm using its pedipalps and then flips its abdomen into the female's mouthparts. This self-sacrificial flip is thought to maximise reproductive success, though males risk being eaten before transferring sperm to a second storage organ.
A study published in Biology Letters by German researchers investigated why redback males perform this somersault, while closely related New Zealand katipō males do not. By breeding female katipō with male redbacks, they found that close to half of the third-generation offspring inherited the somersaulting behaviour, leading them to conclude it is linked to a specific location on the spider's X chromosome.
Evidence suggests interbreeding between native katipō and invasive redbacks is occurring in the wild in New Zealand. Cor Vink, a spider expert at Lincoln University, described the research as an "elegant paper" that illuminates the redback's "weird mating behaviour" and could inform efforts to combat interbreeding.