Chromosome aberrations in field strains of Blattella germanica

Resistant and susceptible field strains of the German cockroach were compared for possible chromosome aberrations. Resistant strain females produced significantly higher numbers of aberrant oothecae ( >5 unhatched eggs ) than the susceptible strains. Chromosome aberrations found in the susceptible strains were attachments (autosome-autosome, autosome-x) and fragments that did not reappear in outcrosses. Attachments (autosome-autosome, autosome-x), fragments, three translocation configurations that did not reappear in outcrosses and two reciprocal translocation heterozygotes occurred in the resistant strains. These two translocations have been tentatively identified as T(12:8)/12:8 from the Bowl strain and T(11:6)/11:6 from the K851 strain. T(12:8)/12:8 exhibits random disjunction at metaphase I. There were no differences related to susceptible vs. resistant strains in the frequency of chromosome aberrations from the aberrant oothecae.

There was no evidence, except in the K851 strain, to support a relationship between egg arrest and chromosome aberrations, or the hypothesis that chromosome aberrations result from the selective pressure of insecticides. It is suggested by this study that translocations are the most common type of “floating” polymorphism in the German cockroach. The first occurrence of three known phenotypic mutants, bent bristle, yellow body, and pallid eye, and one new phenotypic mutant, colorless eye, in field strains are reported by this study.