Karyotypes and meiosis in Gryllus bimaculatus De Geer (Orthoptera: Gryllidae) with a note on the N-banding pattern

SUMMARY

Both mitotic and meiotic chromosomes of Gryllus bimaculatus collected from different populations were studied and the diploid chromosome number was determined to be 2n ♂/♀ = 29/30. The X-chromosome was identified as large and metacentric one. Interestingly, the karyomorphology differs from population to population. Structural heterozygotes were recorded in two cases. The genome lengths varied from 54.04 to 68.67 μm. The meiotic cells (diakinesis/metaphase-I) also revealed 14 bivalents and an univalent X-chromosome showing isopycnotic behaviour. One to two chiasmata were recorded per bivalent. Some polyploid spermatogonial cells up to the extent of hexaploidy were noted. The N-banding pattern (Ag-NORs) of the chromosomes in this species is reported for the first time. N-banding analysis showed the presence of silver deposits on 3 chromosomes of the individuals of Nimapara population and on 2 chromosomes of the individuals of Berhampur population. In certain individuals of the first population 2 to 3 pairs of autosomes revealed mild N-banding.