Knockdown of the GFP transgene in the β-actin-GFP transgenic medaka using a GFP-targeted morpholino. Embryos with or without morpholino treatment were observed at stages 26 and 32 under a fluorescent microscope. β-Actin-GFP transgenic medaka shows green fluorescence in skeletal muscle and lens (left column). Note that the morpholino-treated embryos show almost no green fluorescence (right column). Yellow fluorescence is the autofluorescence of the leucophore.