Cytogenetic characterization of Leptysma filiformis (Acrididae, Leptysminae): a derived karyotype and insights into chromosomal evolution

Within the subfamily Leptysminae Brunner von Wattenwyl, 1893, the most common karyotype is 2n = 23, X0 in males and 2n = 24, XX in females. However, species with derived chromosome numbers are known, such as Tetrataenia surinama Linnaeus, 1764, Nadiacris sp. Descamps et Amédégnato, 1972 (2n = 19, X0) and Stenopola pallida Bruner, 1906 (2n = 21, X0). Some species even present intraspecific variations, such as Leptysma argentina Bruner, 1906 (2n = 19, X0; 2n = 21, X0) and Cornops aquaticum Bruner, 1906 (2n = 23, X0; 2n = 21, X0; 2n = 17, X0). Here, we characterized Leptysma filiformis Serville, 1838 cytogenetically and compared its chromosomal features with those reported for other Leptysminae, providing insights into chromosome evolution within the group. Males presented a diploid number of 2n = 21, X0 with the first chromosome pair being large and metacentric and the remaining chromosomes acro-telocentric. Telomeric mapping with the (TTAGG)n probe revealed terminal signals on all chromosomes. Constitutive heterochromatin showed a conserved pericentromeric distribution across all chromosomes, with an additional distal block on the L 1 and L 2 bivalents. CMA 3 staining revealed GC-rich heterochromatin on pairs M 7 , S 8 , S 9 , and S 10 , with the signals on M 7 , S 8 , and S 9 coinciding with rDNA sites, whereas the S 10 signal was not associated with rDNA. Three rDNA clusters and three transcriptionally active NORs were identified in the cells analyzed. Overall, these findings reveal a combination of karyotypic diversification and conserved cytogenetic patterns, providing new insights into the evolutionary history of Leptysma Stål, 1873 and Leptysminae.