YOUNG, B.A.; DALEY, K.; LEE, C.: The Comparative Anatomy of the Fang Sheath in Snakes

The fang sheath is a drape of connective tissue and epithelium that surrounds the fang of all proteroglyphic and solenoglyphic snakes. The fang sheath is generally described as “supporting” the fang, and recent experimental analyses suggest that it may have a major influence on venom expulsion. The morphology of the fang sheath remains poorly known, particularly within a phylogenetic or functional context. Since the terminal portions of the venom delivery system pass through the fang sheath, an appreciation of this structure is important for a complete understanding of venom delivery. We examined the histological structure of the fang sheath in 21 species, including representative of every major taxonomic group of proteroglyphic and solenoglyphic snakes. The head of each specimen was bisected and decalcified; one side was sectioned frontally and the other parasagittally. Numerous previous workers have argued that the pterygoideus muscle courses, either directly or indirectly via tendinous elements, through the fang sheath to contact the secondary venom duct. This muscular linkage has been interpreted as playing an important functional role in both the mechanics of fang replacement and in the control of venom flow. We found no evidence of this muscular component of the fang sheath in the species we examined. The results of this study do suggest that the fang sheaths of snakes have some consistent structural features which are suggestive of a conserved role in venom delivery.