Embryonic Development of Duvernoy's Gland in the Snake Natrix tessellata (Colubridae)

Abstract

The development of Duvernoy's gland was studied in embryos of the colubrid snake Natrix tessellata. The snakes hatch on the 35th day of incubation at 30 C; the gland primordium and the maxillary dental lamina appear as a joint bifurcated ingrowth of the oral epithelium on the 15th day. The lateral branch gives rise to the gland primordium as perpendicular branches radiate from its main axis. Branching continues at later stages until the gland assumes the general form of a compound acinous gland. Alkaline phosphatase first appeared in the peripheral region of the branches on the 16th day of incubation whereas acid phosphatase was first demonstrable in all parts of the gland on the 20th day. The staining intensity of both enzymes became stronger at later stages of development, with a maximum reaction at two days before hatching. After hatching, the reaction was reduced, almost disappeared in the acini, and was located in the main ducts only, as in adults. After the 28th day the PAS-positive material became gradually resistant to diastase, indicating the appearance of mucosubstances that stained with alcian blue. On the day of hatching, mucous cells were observed in the main duct and PAS-positive diastase-stable granules were seen in the secreting cells of the acini. EMBRYOLOGICAL studies show that, in all snakes studied so far, Duvernoy's and venom glands originate from a primordium in common with the maxillary dental lamina (Kochva,