A comparative histological study of nervous system development in chickens during 24 and 48 hours of incubation

Abstract

This study investigated the early development of the central nervous system (CNS) in chicken embryos, comparing morphological and histological changes between 24 and 48 hours of incubation. A total of 150 chicken egg samples were randomly divided into three equal incubation groups (n=50 per group). To ensure baseline uniformity, initial egg weights were analyzed using one-way ANOVA, which revealed no statistically significant differences between the cohorts (p > 0.05). Following incubation for 1-16,24, and 48 hours, embryos were extracted, fixed in 10% neutral buffered formalin, processed histologically, and stained with Harris hematoxylin and eosin (H&E). Morphological and microscopic examinations demonstrated that after 24 hours of incubation (Hamburger-Hamilton stages HH8–HH9), the embryos were at the neural plate stage, characterized by an open neural groove and elevating neural folds. By 48 hours of incubation (stages HH12–HH13), primary neurulation was completed, showing a fully closed neural tube separating from the surface ectoderm, alongside primary brain vesicle differentiation and adjacent somites. Ocular micrometer measurements showed a significant increase (p≤0.05) in neural tube length and width by 48 hours. It was concluded that the 24 to 48-hour incubation window represents a critical phase for primary neurulation and early brain regionalization governed by intrinsic genetic programs rather than external egg metrics.