Spectacular fluorescence emission in sea urchin larvae

Strong fluorescence emission occurred in sea urchin larvae when irradiated with blue light under a fluorescence microscope. The blue light irradiation first broke red granules in the pigment cells, releasing green fluorescent substance(s) into the cytoplasm of the pigment cells. The released and dis persed fluorescent substance(s) then made the entire pigment cell emit stro ng green fluorescence. With prolonged blue light irradiation, the pigment c ell itself bursted, dispersing the fluorescent substance(s) into the body c avity or seawater. This resulted in "explosive emission" of the fluorescenc e. Cells that can emit such fluorescence first appeared at the late-blastul a stage, proliferated with development, and changed into the red-pigmented cells. Similar fluorescence emission was observed in the larvae of Clypeast er japonicus, Hemicentrotus pulcherrimus, Anthocidaris crassispina and Pseu docentrotus depressus, of which C. japonicus larvae displayed the strongest fluorescence.