Ultrastructural Scale Patterns in Nerodia and Thamnophis

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Abstract
The scales of members of the genera Nerodia and Thamnophis have a basic ultrastructural pattern of pores. Thamnophis is characterized by a canaliculate pattern of longitudinal ridges; Nerodia have a crosshatch-cup pattern. Based on the microsturctural scale patterns, the species valida should be transferred from Nerodia to Thamnophis, and both melanogaster and rufipunctatus would be assigned to the genus Nerodia rather than Thamnophis. With these changes all studied Nerodia also have apical stigmata. The scale pores allow access of an epidermal exudate (containing lipids) to the surface of the scale. Modifications of the basic pore pattern into cup-like chambers may assist in the retention of the exudate on the surface of the scale. Such a coating of fatty material on the surface might form a water barrier on the skin especially advantagenous to aquatic taxa.