Embryonic development of the Giant South American River Turtle, Podocnemis expansa (Testudines: Podocnemididae)

Knowledge of embryonic development is important for choosing strategies for nest conservation, and reducing negative effects on eggs and embryos of turtle species subject to human and natural interference, as is the case of Podocnemis expansa in the Amazon. Nine P. expansa nests located in Balbina, Amazonia, Brazil, were used to describe embryonic development. An embryo was collected each day, totaling 240 embryos. The specimens were fixed in Bouin's and Karnovsky's solutions for macroscopic analysis and scanning electron microscopy, respectively. The incubation period lasted between 58 and 64 days with a mean nest incubation temperature of 30.3 A degrees C. The main characteristics used for description and comparison of embryonic development were: development of the eyes, the mandibular process, limbs, carapace and plastron. We found that the timing of appearance and disappearance of structures in P. expansa were more advanced than in other turtle species. Furthermore, P. expansa displays some unique characteristics during its normal development, such as craniofacial morphology, frontonasal groove and carapace and plastron characteristics.