Fig. 4.

—Immunohistochemistry of a butterfly retinochrome, unclassified opsin (UnRh). UnRh is expressed in several kinds of cells found in the distal retina but not in photoreceptor cells. (A) Drawing of a butterfly ommatidium showing the cornea (c), crystalline cone (cc), rhabdom (r), photoreceptor cells (R1-9), primary pigment cells (ppc), secondary pigment cells (spc), and basement membrane (bm) based on Kolb (1985). Red represents areas where UnRh expression is detected, dark red indicates where the cell presumably narrows and staining is not as bright. A drawing of a cross section shows cells R1-8, blue cells represent LWRh staining and red circles represent UnRh staining. (B) Brightfield image of a longitudinal section of a Heliconius melpomene eye showing the anatomy of each ommatidium and an intact cornea. (C) Fluorescent image of the same section stained for opsins using rabbit anti-LWRh (blue) and guinea pig anti-UnRh (red) antibodies. (D) Transverse section stained for opsins LWRh (blue) and UnRh (red).