Comparative Aspects of the Hemipenial Architecture of the Arabian Horned Viper <i>Cerastes gasperettii</i> : Macroscopic and Microscopic Analysis With Evolutionary Perspectives

This study presents the first detailed description of the hemipenial architecture of the Arabian horned viper Cerastes gasperettii. The study utilized five adult males collected from Aljouf Province, Saudi Arabia. Macroscopic and microscopic analyses addressed the morphology, histology, and histochemistry of the hemipenis. The hemipenis was a paired and bilobed organ situated at the tail base. The apex was ornamented distally by several spines of variable size, whereas the body region was nude. The sulcus spermaticus was bifurcated distally and represented by a prominent groove that traverses the external surface of the everted organ. Microscopically, the hemipenis was coated by a non-keratinized stratified epithelium, supported by the underlying connective tissue, two concentric cavernosum bodies, and muscular components. The musculus retractor penis magnus was recognized internally, while the cavernosum bodies were encircled by a ring of smooth muscle, intermingled with the connective tissue. Interestingly, the hemipenial spines were supported by a fibrocartilaginous core, providing a structural and functional specialization. The obtained results provide new insights into the hemipenial anatomy and microanatomy of the Arabian horned viper (C. gasperettii), which contribute to a broader understanding of the hemipenial evolution among squamates, species-specific reproductive patterns, and phylogenetic relationships.