Giant rhabdomes in a specialized region of the compound eye of a cricket: Cycloptiloides canariensis (Insecta, Gryllidae)

Abstract

The cricket Cycloptiloides canariensis (Gryllidae, Mogoplistinae) has compound eyes of the eucone apposition type. They consist of relatively few (about 160–190) ommatidia with a wide angle of divergence. Each ommatidium has two primary pigment cells, four Semper cells and eight retinula cells whose four distal rhabdomeres are arranged around the tip of the crystalline cone. The screening pigments are contained mainly in the primary pigment and retinula cells, while the secondary pigment cells are sparsely pigmented. The dorsal eye region can be distinguished by the following characteristics: lack of dioptric apparatus (flat, unfacetted cornea, absence of cones), densely packed rhabdomes in approximately parallel orientation extending distally to the cornea and possessing a markedly increased cross-sectional area in comparison with those of normal ommatidia. Screening pigments are absent. The importance of this dorsal region will be discussed.