SELECTION OF A STRAIN OF AEDES-AEGYPTI SUSCEPTIBLE TO DIROFILARIA-IMMITIS AND LACKING INTRACELLULAR CONCRETIONS IN THE MALPIGHIAN TUBULES

In the process of selecting strains of Aedes aegypti refractory and susceptible to Dirofilaria immitis, we coselected for mosquitoes in the susceptible strain that lacked intracellular concretions in the cells of the Malpighian tubules. Using light and electron microscopy we were able to show that the cells lack both the crystals and the vacuoles surrounding them which are characteristic of the primary cells in the Malpighian tubules. Electron-probe microanalysis of whole tubules demonstrates that the tubules lacking crystals are also depleted in calcium, magnesium, manganese and phosphorus, compared to tubules from the refractory strain which contain crystals. Tests with larvae from these strains were unable to demonstrate increased mortality in larvae lacking intracellular crystals, either in media low in free calcium and magnesium, or in media high in zinc, manganese and magnesium. The genetic basis for the lack of crystals and the relationship of this trait to the susceptible condition are not yet known. © 1990.