Comparison of anatomical and histological characteristics of vomeronasal organ in two aglypha snakes of Eirenis collaris and Typhlops vermicularis

In snakes Vomeronasal organ (VNO) is a well-developed organ involved in both mating and hunting. To investigate histomorphometry on this organ, 5 individuals of Eirenis collaris and 6 specimens of Typhlops vermicularis were collected from their natural habitats. Following biometrical and anatomical examinations, only the head of specimens were processed for histological assessments. Based on our studies, it was found that as other snakes, in these species the VNO is a tubular structure located at the roof of the oral cavity just beneath the nasal cavity. This organ through a canal opens to the oral cavity but there is no connection between the VNO and the nasal cavity. Histologically, the wall of VNO is covered with three epithelia (sensory, non-sensory and intermediary). Despite many similarities, some differences were also found between E. collaris and T. vermicularis. In addition to a lager size of the VNO in E. collaris than T. vermicularis, the nasal septum in E. collaris does not participate in the capsule surrounding the organ. In addition, the sensory epithelium in T. vermicularis is thinner than the same epithelium in E. collaris where there is a distinct boundary between columnar apical cells and underlying cells. Moreover, the epithelium covering the mushroom body is a ciliated columnar in T. vermicularis but this tissue is ciliated stratified cuboidal in E. collaris. In general, this study showed the VNO in E. collaris is more developed than its corresponding organ in T. vermicularis and this difference is also reflected in their living manner.