Intercellular junctions and rhombic particle arrays in the developing and adult dorsal ocelli of the honeybee

Abstract

Intercellular junctions and particle arrays in the developing and mature dorsal ocelli of the honeybee Apis mellifera have been studied with conventional and freeze-fracture electron microscopy. Four types of junctions are found in the lentigenic and retinogenic part during development. These are desmosomes, septate junctions, tight junctions, and gap junctions. Gap junctions and septate junctions are found between differentiating photoreceptor cells only as long as the rhabdoms are beginning to form. Their disappearance after differentiation indicates that they could play a part in cell determination. Desmosomes connect photoreceptor cells into the early imaginai stage and then disappear. Other junctions, once they have formed, remain for the life of the animal, but can change considerably in structure, distribution and frequency. The cells of the perineurium surrounding the ocellus are connected by septate and gap junctions, which may be the basis of the blood-eye barrier. Rhombic particle arrays on the E-face of the glial membrane attached to the photoreceptor cell membrane first appear in small groups one day before emergence. In the further course of life these arrays become more extensive and apparent. Their significance may be to play some role in receptor function. © 1989.