Passage of Harderian gland secretions to the vomeronasal organ of Thamnophis sirtalis (Serpentes: Colubridae)

Abstract

The Harderian gland is a poorly understood structure found in the anterior orbit of most terrestrial vertebrates. In colubrid snakes it is a seromucous gland with a large postorbital portion. Numerous functions have been ascribed to this gland, including contributions to orbital lubrication or the vomeronasal system. Anatomically the Harderian gland is connected to the vomeronasal organ (VNO) via the nasolacrimal duct. In this study we traced the serous secretions of the Harderian gland of two subspecies of Thamnophis sirtalis (Colubridae), using autoradiographic techniques at the light-microscopic level. We injected the Harderian gland of the snakes with H3-proline either unilaterally (right side) or bilaterally. The right Harderian glands of both treatment groups were then injected with a potassium-rich solution. No labeling was observed in the orbital space of any treatment group, suggesting that the Harderian gland secretions of T. sirtalis do not function in orbital lubrication. Labeling was only observed in the right Harderian gland, Harderian gland ducts, nasolacrimal duct, apical vomeronasal sensory epithelium, VNO lumen, and vomeronasal duct. No such labeling was observed in any of the other treatments examined. Thus, the serous secretions of the Harderian gland in snakes flow to the VNO, and may be considered part of the vomeronasal system. The specific function of the Harderian gland secretions in the vomeronasal system remains to be determined.