Researchers from Harvard University have discovered that the male octopus's penis-like arm, the hectocotylus, is also a sensory organ that can detect where sperm needs to go. The research, which also shed light on the evolution of octopuses, was conducted through experiments at the university and elsewhere. The findings could help explain how they evolved into the hundreds of different species. The hectocootylus is crucial to octopus mating, but it can be difficult to study up close due to the solitary nature of these animals. The researchers identified the progesterone-sniffing receptor as CRT1, a receptor also used to detect bacteria found on prey. They also found that the genetics of these receptors have undergone rapid changes in evolutionary time.