Can an orbital gland function in the vomeronasal sense? A study of the pygopodid Harderian gland

The Harderian gland occurs in the orbit of most tetrapod vertebrates. A gro wing body of evidence suggests that this gland is associated with the chemo receptive function of the vomeronasal organ. In the present study, the morp hology of the Harderian gland in two species of pygopodids was examined, an d the results were contrasted with those from both geckos and snakes. The r esults show that the pygopodid Harderian gland shares histochemical and ult rastructural features with that of the geckos. However, in several gross mo rphological features, the pygopodid Harderian gland more closely resemble t hat of snakes than that of geckos. In both pygopodids and snakes, the nasol acrimal duct forms a direct link between the Harderian gland and the vomero nasal organ, which indicates that this specialized connection between the H arderian gland and vomeronasal organ is a convergent evolutionary attribute of these two groups.