Effects of Nosema algerae infections on the gene activity of the salivary gland chromosomes of Acricotopus lucidus (Diptera, Chironomidae).

Larvae of Acricotopus lucidus (Diptera, Chironomidae) were successfully infected with Nosema algerae (Microsporidia, Nosematidae). Treatment of newly hatched larvae with 2-3 x 10(5) spores/ml produced a 59.7%-83.8% rate of microsporidia-infected animals within 6 weeks. One of the host tissues infected was the polytene salivary gland; 31.3%-35.3% of the larvae showed infections in the gland cells. This made it possible to investigate the reaction of the puffing pattern of the polytene host-cell chromosomes to the presence of an intracellular parasite. In slightly or moderately infected salivary gland cells, no change in the regular puffing patterns was observed. Only in heavily infected cells did an inactivation of cell-type-specific Balbiani rings and puffs occur, resulting in a change in the cell-type-specific genetic programme.