Embryonic development of Kinosternon scorpioides (Testudines: Kinosternidae)

Few studies have been conducted on the reproductive biology and embryology of Kinosternon scorpioides. Determining the development of embryonic stages is essential for studies on comparative anatomy and phylogenetic relationships. The aim of this research was to examine the macroscopic embryonic development of K. scorpioides . At least three eggs were collected at incubation intervals of 5 days. After morphometry, embryos in stages 9–12 were classified in relation to the presence of pharyngeal arches, optic and otic vesicles, as well as sequential changes in both the forelimbs and hindlimbs. Embryos from stages 13 to 17 were identified through evident eye pigmentation, limb morphology, carapace appearance, and urogenital protuberance. From stages 19 to 22, the presence of digits on digital plates and pigmentation of the body were used for defining each of the stages. From stages 23 to 26, the digits and dense pigmentation on the body were used to define the stages and the disappearance of the urogenital protuberance and umbilical hernia. These results describe the ontogenetic changes that occur in this species, therefore facilitating the correct ex situ handling practices during incubation and serving as a basis for phylogenetic studies among the Kinosternidae.