Widespread losses of vomeronasal signal transduction in bats.

The vertebrate vomeronasal system (VNS) detects intraspecific pheromones and environmental odorants. We sequenced segments of the gene encoding Trpc2, an ion channel crucial for vomeronasal signal transduction, in 11 species that represent all main basal lineages of Yinpterochiroptera, one of the two suborders of the order Chiroptera (bats). Our sequences show that Trpc2 is a pseudogene in each of the 11 bats, suggesting that all yinpterochiropterans lack vomeronasal sensitivity. The Trpc2 sequences from four species of Yangochiroptera, the other suborder of bats, suggest vomeronasal insensitivity in some but not all yangochiropterans. These results, together with the available morphological data from the bat VNS, strongly suggest multiple and widespread losses of vomeronasal signal transduction and sensitivity in bats. Future scrutiny of the specific functions of the VNS in the few bats that still retain the VNS may help explain why it is dispensable in most bats.