Dynamic Morphological Staging of Drosophila Pupal Development

This study provides a comprehensive analysis of the morphological-developmental characteristics of the pupal stage in Drosophila , a model organism for metamorphosis research. We have delineated the critical stages of pupal development, from the late third-instar larvae to the adult emergence, through continuous photography and time-lapse imaging. Our findings include the identification of the head-movement phase and head-static period as distinct transitional states preceding the pupal stage. We describe the dynamic changes in the pupal shell, including color transitions and the development of spiracles, which serve as reliable markers for staging. Additionally, we detail the morphological transformations of internal tissues and organs, such as the degeneration of larval tracheae, the retraction and degeneration of mouthparts, the formation of compound eyes and wings, and the development of appendages and bristles. Our research also highlights the significant morphological changes in pupal tissues, including the movement and displacement of bubbles, the appearance and migration of Malpighian tubules and corpora allata. In conclusion, we have identified several critical periods: P10 serves as a definitive marker for the onset of segmentation during the pupal stage, P40-P50 represents an optimal period for observing the initiation of changes in eye and wing coloration, and P70 marks the beginning of the investigation into the morphological changes of the adult within the Drosophila pupal case. We also found that compared with wild-type Drosophila , mutant fruit flies showed some differences in development time and pupal tissue organization. These observations offer a detailed developmental map of the Drosophila pupal stage, which is essential for accurate experimental staging and sampling. This study's findings not only contribute to the fundamental understanding of insect metamorphosis but also provide a valuable resource for researchers utilizing Drosophila as a model system to study gene expression, development, and behavior.