Non-invasive visualization of physiological changes of insects during metamorphosis based on biophoton emission imaging

Spontaneous ultra-weak photon emission from living organisms, designated as biophoton emission, is a generally observed phenomenon irrespective of the organism species. Biophoton emission is attributed to the production of excited molecules in a metabolic biochemical reaction, especially in processes involving reactive oxygen species (ROS). Although many plant and mammal subjects have reportedly been used to study its application to biological measurements, biophoton emission properties of insects remain unclear. For this study, we strove to measure the variation of two-dimensional images of biophoton emission during the metamorphosis of lepidopterous insects as a moving picture to elucidate the physiological changes underlying the mechanism of drastic changes of morphological and ecological characteristics of the insects. We used our developed biophoton imaging system incorporating a cooled charge-coupled device (CCD) camera and a specially designed lens system to elucidate the spatiotemporal dynamics of biophoton emission during metamorphosis, larval–pupal ecdysis/pupation of Papilio protenor, suggesting its applicability for in vivo observation of physiological changes during the regulation of metamorphosis.