Chromosome polymorphisms and chiasma frequency in two populations of Staurorhectus longicornis (Orthoptera-Acrididae).

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Abstract
Karyotype and meiotic behavior were analyzed in 2 Argentine populations of S. longicornis. The basic karyotype in this species is composed by 23 telocentric chromosomes in males (22 autosomes + X) with a sexual mechanism XO .male..male..XX .female..female.. Chromosome variations involving a centric fusion, a pericentric inversion, elastic constrictions and a supernumerary segment were detected. The study of chiasma frequency and movement allowed to establish that: there is a continuous chiasma movement and terminalization from diplotene to MI; the differences between populations are non significant though there is a high within population variability; the rearrangements observed have no obvious influence on chiasma conditions. C-banded meiotic karyogram at diplotene, made with Ba (OH)2 and 2 .times. SSC [0.15 M NaCl/0.15 M trisodium citrate], is described. It demonstrates centromeric, interstitial and telomeric bands in meiotic autosomes. The X and megameric pair were totally heterochromatic.