Post-Oviposition Embryonic Staging Scheme for the Delicate Skink, Lampropholis delicata

Skinks are an important model in evolutionary research because they have evolved a suite of features of interest in vertebrate biology, from limb loss to viviparity. Furthermore, they have been a model for understanding ecophysiology and behavior, particularly the impact of climate change on ectothermic animals. Despite studies on the impact of developmental processes on skink biology, researchers have relied on embryonic staging schemes from species that diverged from skinks over 170 million years ago. We describe Lampropholis delicata as a model and establish the first embryonic development staging scheme for a skink. We detail the morphology of post-oviposition embryos at different stages and compare them with other reptile lineages. Embryos across 14 stages are described based on the development of limbs, eyes, brain, branchial arches, frontonasal prominence, otic vesicle, scales, and pigmentation. We distinguish early stages via the shape of the otic vesicle, and find the pineal organ is present earlier than in Zootoca and Anolis embryos. This skink embryonic staging scheme serves as a valuable tool for ongoing research into skink biology and can be used as a benchmark for genetic, evolutionary, and physiological research.