Ultrastructure of the lateral eye ofProtzia constans(Marshall) (Acarina: Hydryphantidae)

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Abstract
The eyes of Protzia constans consist of anterior and posterior biconvex lenses that are lamellate and have a thin cuticular layer with pore canals on the dorsal surface. There are four retinula cells beneath each lens and no vitreous cone or preretinal membrane is associated with either lens. The rhabdomeres are in direct contact with the lenses and are fused into a single rhabdom. The visual pigments are situated under each rhabdomere and along the sides. Secondary pigments are concentrated between the cuticule of the body and the retinula cells, and between the retinular regions under each lens. These pigments are a type of lipid(s) that provide a barrier to extraneous light. The cuticle of the eye capsule forms a long extension that reaches into the body cavity and a muscle is attached to the cuticular estension. This muscle is probably capable of changing the position of the lateral eye in respect to the light