Fig. 1. Anatomical overview of an L. rubidus ommatidium and non-opsin pigment expression. (A) Diagram of a typical ommatidium. Longitudinal (left) and transverse (right) view of an ommatidium located in the ventral domain of the eye. Purple pupillary pigments are present in R1-8 photoreceptor cells regulating the amount of light entering the ommatidium. (B) The dorsal eye lacks the pink filtering pigment. Transverse unstained Epon sections were examined by DIC microscopy. Arrows denote rhabdoms (rh). (C) In the ventral eye, most ommatidia contain a pink filtering pigment (arrowheads), which is lacking in other ommatidia (arrow). Basement membrane (bm), cornea (c), rhabdom (rh), tapetum (tp), crystalline cones (cc). Scale bars, 5 µm (A), 10 µm (B).