title: The cytogenetic structure of Tasmanian populations of Phaulacridium vittatum.
abstract: In 8 out of 20 Tasmanian populations of Phaulacridium vittatum from 0.3-11.0 percent of the males carried a single supernumerary chromosome. In such males the X and B univalents are both heteropycnotic at first prophase of male meiosis and associate with another in a non-homolgous manner in about two-thirds of the diplotene cells examined. In all 56 B-containing individuals studied, however, these associations lapse by first metaphase and the X and the B move at random with respect to one another at first anaphase. The supernumerary in this species is stable and only 5 of the 56 individuals with supernumeraries showed evidence of B-chromosome non-disjunction in the pre-meiotic mitoses. Since there was no other evidence for the loss or gain of supernumeraries in the male line it is clear that B-transmission is regular in the males of this species. There were significant differences between population with respect to mean cell chiasma frequency but there was no significant effect of the B-chromosome on this metric. Additionally a comparison of mean cell chiasma frequency in follicles with and without supernumeraries from a mosaic individual shows no significant difference.
mesh_terms: D000818:Animals; D001315:Australia; D002875:Chromosomes / Q000648:ultrastructure*; D002980:Climate; D003434:Crossing Over, Genetic; D005828:Genetics, Population; D006110:Grasshoppers / Q000648:ultrastructure*; D008297:Male; D008540:Meiosis; D009030:Mosaicism; D012730:Sex Chromosomes / Q000648:ultrastructure