Study of the adaptation of snakes to the specificity of their diet: comparative anatomy of the cephalic glands in three species of the Tachymenini tribe (Dipsadidae, Xenodontinae)

Abstract

Despite the importance of the cephalic glands for the characterization and diversification of advanced snakes, little is known on their morphological diversity. The scarce bibliography is restricted to venom glands, one of the most studied gland among vertebrates. Even so, within snakes with posterior fangs, known as non-front-fanged snakes (NFFs), little is known about the anatomy and evolution of venom glands. Snakes of the Tachymenini tribe (Dipsadidae, Xenodontinae) are characterized by the presence of muscle fibers attached to venom glands, a rare condition among NFFs. However, there is no detailed information about this condition for any species belonging to this tribe. In addition, these snakes show a wide variation in their diet, with some genera consuming mollusks and annelids, a feature that has been related to the loss or atrophy of venom glands. The present study aims to analyze the anatomy, histology and histochemistry of the main cephalic glands (venom, supra and infralabials, and Harderian), as well as, associated structures such as musculature and dentition of the following species of Tachymenini: Tomodon dorsatus, Thamnodynasthes strigatus, and Gomesophis brasiliensis. The glandular anatomy will be described and the collected data set will be analyzed comparatively. Based on the results obtained in this project, we will better understand the morphological variation of the cephalic glands of these snakes, and we will be able to relate the gland morphology with the diet for each specie, besides we will describe in detail the association of the venom glands with the adjacent musculature. These results will also be used to understand the mechanisms of variation of the venom composition and transcriptomics, within the working frame of the Dimensions project - Scales of Biodiversity (FAPESP 2016/50127-5).