VARIABILITY OF CENTROMERIC CHROMATIN IN CHROMOSOME-2 OF OVARIAN NURSECELLS IN INBRED MOSQUITO ANOPHELES-ATROPARVUS V. TIEL

We investigated the variability of pericentromeric chromatin of chromo some 2 in ovarian nurse cells (trophocytes) in two laboratory lines of malaria mosquito Anopheles atroparvus V. Tiel and in their hybrids. O ne line had been raised by means of sib inbreeding, the other kept at constantly high population density. The inbreeding was shown to result in an increased percentage of chromosomes bearing an achromatinic zon e in the centromeric region, which resulted in chromosome breakage. To xicological tests demonstrated an increase in the sensitivity of the p rogeny of females with abnormal morphotypes of chromosome 2 to the ent omopathogenic bacterium Bacillus thuringiensis israelensis. The appear ance of the achromatinic zone is attributed to local chromatin underre plication accompanying chromosome polytenization. Possible reasons for this phenomenon and its implication for adaptation are discussed.