Co-expression of Mnemiopsis photoprotein ( MleiPP1 ) and opsin ( MleiOpsin2 ) mRNA expression. All images are lateral views of a cydippid approximately 18 hpf and a double asterisk denotes the aboral pole of the embryo. (A) Green staining is MleiPP1 mRNA expression via fluorescence in situ hybridization (fluorescein probe). (B) Dark blue staining is MleiOpsin2 mRNA expression via nitro blue tetrazolium (NBT) and 5-bromo-4-chloro-3-indolyl phosphate (BCIP) (digoxigenin probe). (C) Reflective confocal microscopy of co-fluorescent in situ embryo shown in (A) and (B). Bright blue staining is nuclei via 4'-6-diamidino-2-phenylindole; green staining is MleiPP1 mRNA expression via fluorescence in situ hybridization; red staining is MleiOpsin2 mRNA expression via NBT/BCIP.