The penial and bacular morphology of the solitary silvery mole-rat (Heliophobius argenteocinereus, Bathyergidae) from Malawi and evolutionary patterns across the African mole-rat family

Abstract

The silvery mole-rat (Heliophobius argenteocinereus) is a solitary, subterranean bathyergid rodent that lives in savannahs in Eastern Africa. Our study focuses on its penial and bacular morphology with respect to its mating strategies, degree of sociality, ovulation type and seasonality of breeding. The penis morphology fits into the trend in bathyergids, where solitary species have a more ornamented penis. Interestingly, the longest penile spines within the bathyergids were detected in this species. Results from the measurements of the penis bone did not match the predictions that the sociality is associated with a smaller baculum size. Moreover, so-called eusocial bathyergids have, relatively, the longest bacula within the family. Our parsimony reconstruction of the ancestral state indicates that the common ancestor of bathyergids probably lived in a group and had an induced ovulation and penis without the ornamentation.