Fine-structural details of the photoreceptor membranes in the ocellus of the scale-insect parasite Centrodora sp. (Hymenoptora; Aphenelidae): a case of gene transfer between host and parasite?

ABSTRACT

Only one insect (the scale insect Eriococcus sp.) is known, in which photoreceptive lamellae appear to have replaced the usual arthropod rhabdom microvilli. We are now reporting the presence of photoreceptive membranes, which also appear to resemble lamellae rather than microvilli, but they are in the ocellus of the tiny wasp Centrodora sp., which parasitizes scale insect eggs. The apparently optically homogenous lens of the Centrodora ocellus measures approximately 10 µm in diameter and, thus, operates at the limits of diffraction. We calculated that the lens is capable of focusing a parallel bundle of rays on the retina of the ocellus.