Pre-oviposition development of the brown anole (Anolis sagrei).

Background: The brown anole, Anolis sagrei, has emerged as a representative squamate species for developmental studies during the past decades. Novel functional tools have been established to manipulate embryogenesis through genome editing or the introduction of small molecule inhibitors, and their effective use requires a thorough understanding of early anole embryogenesis. To enable precise and reproducible staging of anole embryos, we need knowledge of the progression of anole embryogenesis and morphogenesis. While post-oviposition development has been described, the pre-oviposition period remains to be explored.

Results: We provide the first staging series of pre-oviposition development for the brown anole. Analyzing the follicles and embryos through brightfield imaging, SEM, STEM, histology, and DAPI staining, we define 26 distinct developmental stages. Furthermore, we followed heart development, neural crest cell migration, and central nervous system development using immunofluorescence analyses and provide new comparative insights into the morphogenesis of each of these organ systems.

Conclusions: Our dataset reveals that peri-gastrulation morphogenesis up to the initiation of neurulation diverges significantly from chick, the common representative model of reptile embryogenesis. With this study, we establish the brown anole as a squamate model organism for cross-clade evolutionary studies of early embryogenesis.