Shedding Light on the Dentition and Venom Delivery System of the Rear-Fanged Snake, Galvarinus chilensis chilensis (Serpentes: Dipsadidae: Tachymenini) from Chile

SIMPLE SUMMARY: Studies about dentition and venom delivery systems (fang and gland) of rear-fanged snakes are limited. In Chile, the Galvarinus genus is represented by G. chilensis (formerly named Tachymenis chilensis), whose bites produce mild-to-moderate human envenomation. In this study, we describe the dentition and characteristics of fangs and their ontogenetic variations in G. chilensis chilensis. Moreover, histological and histochemistry analyses of the venom glands of this species are presented. Using micro-computed tomography and scanning electron microscopy, the dentitions of neonates, juveniles, and adults were analyzed. No ontogenetic and sex variations were observed. On the other hand, the fangs exhibited a groove with prominent ridges formed. Notably, the fang and groove lengths were significantly distinct between the three ontogenetic categories. However, we observed no differences between females and males. Using histological techniques, we found that the venom gland is close to the fangs, and the venom gland is constituted by acid mucous and serous acini, suggesting that it is a seromucous gland. Our results describe, for the first time, the distributional pattern and characteristics of the dentition and venom delivery system of the poorly studied snake G. ch. chilensis. ABSTRACT: Although the rear-fanged snake Galvarinus chilensis chilensis (formerly named Tachymenis ch. chilensis) causes ophidian accidents with clinical importance in Chile, the anatomical and histological characterizations of the venom delivery system (venom gland and fang) of this species still remain unknown. This study describes the dentition and characteristics of fangs and their ontogenetic variations in G. ch. chilensis. Moreover, histological and histochemistry analyses of the venom glands of this species are presented. Using micro-computed tomography and scanning electron microscopy, the dentitions of neonates, juveniles, and adults were analyzed, and no ontogenetic variations in teeth length and number present in the dentary and maxilla were observed. Moreover, we found three types of basic teeth, with distributional patterns conserved in all ontogenetic categories. The fangs exhibited a groove from the base to the middle. At the end of the groove, prominent ridges are formed. The fang and groove lengths were significantly distinct between ontogenetic categories. No differences between females and males were observed. Histologically, we found that the venom gland is close to the fangs and has a seromucous composition. Our results describe, for the first time, the distributional pattern and characteristics of the dentition and venom delivery system of the poorly studied snake G. ch. chilensis.