Fine structure of the eyes of orb-weavers, Argiope amoena L. Koch (Araneae: Argiopidae)

Abstract

The anteromedial eye of the web-building spider, Argiope amoena has been examined with light and electron microscopy. The eye consists of a cornea, a lens, a vitreous body and a retina. The retina contains 400 to 500 bipolar photoreceptor cells and pigment ce-ls which envelop the receptor cells. Microvilli extend laterally from the distal process of each receptor cell beneath the vitreous body. The microvilli interdigitate with those from neighboring processes to form rhabdoms. Multivesicular bodies occur in the rhabdomeric portion, and in an intermediate segment, between the rhabdomeric portion and the receptor cell body, are found mixed lamellar vesicular bodies and lamellar bodies. A single axon extends from the receptor cell. The site of origin of the axon from the cell varies depending on the location of the cell in the retina. The axon originates on the intermediate segment, or on the lateral surface or proximal end of the cell body. The axons join together in the postero-dorsal region of the eye and then extend to the first optic glomerulus as an ocellar nerve of about 3 mm in length. The pigment cells, whose cell bodies lie among those of the receptor cells or the axons, possess cytoplasmic prolongations which reach up to the vitreous body.