Morphofunctional structure of the hemocyte population in Galleria mellonella L. (Lepidoptera: Pyralidae) during infection

Using marker enzymes, we have identified certain cell pools in the subpopulation of hemocytes in hemolymph of W-th instar larvae of G. mellonella. The markers used were phenoloxidase, peroxidase, and esterase. We studied changes in the population structure of hemocytes during the infection process and in response to suboptimal temperature (22 degrees C). Esterase activity was present in virtually all hemocytes (90-97%) irrespective type. The amount of cells with esterase activity did not change either upon infection with Bacillus thuringiensis ssp. galleriae or in response to the low temperature. Peroxidase activity could be found in all granulocytes and in part of plasmatocytes and prohemocytes. The number of peroxidase-positive hemocytes did not change during the infection, irrespectively of the technique used to infect the larvae, but diminished drastically at the lower temperature (from 73 to 3%). When bacteria were injected into the larvae, the amount of phenoloxidase-positive cells increased (maximally up to 10% after one day) and sharply diminished three days after the injection. When the infection was achieved by the oral route, the decrease in the number of phenoloxidase-positive cells (down to 0.1%) could be seen one day later. The suboptimal temperature did not affect the amount of phenoloxidase-positive hemocytes. Reduction of nitroblue tetrazolium (NET) in plasmatocytes and granulocytes has been demonstrated. The amount of cells capable of reducing nitroblue tetrazolium increased 4 h after the injection of bacteria into the larval hemocel. When luminol was used, we did not find any significant increase in chemiluminescence.