BLOOD-EYE BARRIER OF THE DEVELOPING DROSOPHILA-MELANOGASTER (DIPTERA,DROSOPHILIDAE)

For the past quarter century, it has been known that a blood-eye barri er exists in adult insects. However, the life stage at which the barri er arises and the anatomical correlate of the barrier were not known. Compound eye development in Drosophila melanogaster (Diptera: Drosophi lidae) is essentially complete at approximately 140 h after pupariatio n; or about 20 h prior to eclosion. A search for a brood-eye barrier s panned late third-instar larvae, through late pupal life sampled at 40 and 140 h post-pupariation. No blood-eye barrier is present in the ey e discs of last-instar larvae, based on the presence of lanthanum trac er among ommatidial cells and their processes. Pleated-sheet septate j unctions, which link larval ommatidial cells, are not yet capable of t otally blocking tracer from paracellular passage. The blood-eye barrie r is constructed in the early phase (0-60 h) of pupal development in t he wake of apoptosis and new cellular reorganization. In the developin g compound eye, mature photoreceptor neurons must then be protected fr om the ionic vagaries of hemolymph to become electrophysically compete nt. First vestiges of a barrier with occluding septate junctions are s een in the 40-h old pupa, and by 140 h, the barrier is complete. The b arrier prevails throughout adult hfe. (C) 1998 Elsevier Science Ltd. A ll rights reserved.