Submicroscopic anatomy of photoreceptors in the female scale insect Eupulvinaria hydrangeae (Homopteres, Coccideae)

The submicroscopic anatomy of the eye in female Eupulvinaria is described. This scale insect has no compound eyes but simple pericerebral eyes composed of one pair of ocelli. The ocelli, located dorsolaterally to the brain, are of rhabdomeric type. They are situated in the subepidermal region underneath the basement membrane of the epidermis. Each ocellus consists of a cup made of a layer of numerous pigmented cells enclosing a few photoreceptive cells. The cuticular lens is facing the opening of the pigment-cup, while the optic nerve is emerging from the bottom of the cup. Pigmented cells show characteristic pigment granules. They are linked to each other by interdigitations or by desmosomes junctions. Both dendrites and cell body of the photoreceptor cell lie inside the eyecup, while the axon lies outside. The dendritic processes consist of large shaft-shaped rhabdomeres with microvilli extending perpendicular to the direction of the shaft. These microvilli are enveloped by digitiform cytoplasmic extensions of pigmented cells. These latter strands are free of pigment granules but contain microtubules orientated to the centre of the cup.SCOPUS: ar.j