A California two-spot octopus Norbert Wu/ Minden Pictures/ Alamy
The earliest known sex chromosomes have been found in an octopus species native to the Pacific Ocean. These chromosomes evolved up to 380 million years ago, and they are the first evidence of genetic sex determination in cephalopods – a group that includes squid, cuttlefish, octopuses and nautiluses.
“Cephalopod sex determination has been a complete mystery up to this point,” says Andrew Kern at the University of Oregon. Researchers have long thought that cephalopod sex is determined by environmental factors, such as temperature. But Kern and his colleagues have found otherwise.
