Uncovering the Dynamics of Parhyale hawaiensis Embryogenesis With In Vivo Hybrid Photoacoustic and Fluorescence...

Parhyale hawaiensis is an amphipod crustacean which has become an essential model organism for filling taxonomic gaps and advancing investigations in developmental and regenerative biology. In this context, optical microscopy techniques are currently used as effective in vivo imaging methods for studying the Parhyale. In this study, we present an alternative hybrid photoacoustic and confocal fluorescence microscope suitable for long-term dynamic imaging of Parhyale embryogenesis. The imaging system incorporates contrast from autofluorescence or nuclear fluorescent labels and photoacoustic detection of endogenous absorbers, such as pigmented yolk, visualizing aspects of morphogenesis that are not accessible to either modality alone. Prolonged tracking of nuclear dynamics and yolk distribution in early organogenesis is performed without compromising embryo viability, and a careful optimization of irradiation and imaging parameters minimizes photobleaching effects. To our knowledge, this is the first demonstration of time-lapse hybrid photoacoustic and fluorescence imaging in a microscopic model organism, enabling long-term acquisitions of crucial structural and molecular features during development. In addition to Parhyale, our approach provides a new platform for studying the interplay of genetic programs and morphogenetic processes in other model organisms, thus extending the imaging toolkit available for developmental biology.