Growth-deficient vomeronasal organs in the naked mole-rat (Heterocephalus glaber)

The naked mole-rat (Heterocephalus glaber) is unusual in numerous life history characteristics as well as its eusocial organization. This species demonstrates widespread sexual suppression and prominent scent marking, behaviors that have been associated with pheromonal communication involving the vomeronasal organ in other rodents. Yet, previous studies indicate that urinary signals do not mediate sexual suppression in Heterocephalus. Surprisingly, no previous studies have examined the vomeronasal organ in this species. Here, we show that Heterocephalus is unique among rodents in showing no evidence of postnatal volumetric growth in the vomeronasal neuroepithelium. Subadults from birth to weaning fell within the same volume range as adults regardless of breeding/non-breeding status of the latter. A comparison of existing ontogenetic data on other mammals suggests that the proportionally small VNOs of Heterocephalus may be explained by a deficiency in VNNE growth. Growth deficiency of the vomeronasal organ in Heterocephalus may relate to a diminished role that pheromones play in certain social interactions for this species, such as breeding suppression. In light of the unique aspects of the vomeronasal organ in Heterocephalus, comparative studies of rodents may provide a model for understanding variation of this sensory system in other mammalian orders including primates, an order which shows a range from vestigial to demonstrably functional vomeronasal organs.