The grasshopper species Orthoscapheus rufipes and Eujivarus fusiformis were analyzed using several cytogenetic techniques. The karyotype of O. rufipes, described here for the first time, had a diploid number of 2n = 23, whereas E. fusiformis had a karyotype with 2n = 21. The two species showed the same mechanism of sex determination (XO type) but differed in chromosome morphology. Pericentromeric blocks of constitutive heterochromatin (CH) were detected in the chromosome complement of both species. CMA(3)/DA/DAPI staining revealed CMA(3)-positive blocks in CH regions in four autosomal bivalents of O. rufipes and in two of E. fusiformis. The location of active NORs differed between the two species, occurring in bivalents M(6) and S(9) of O. rufipes and M(6) and M(7) of E. fusiformsi. The rDNA sites revealed by FISH coincided with the number and position of the active NORs detected by AgNO(3) staining. The variability in chromosomal markers accounted for the karyotype differentiation observed in the tribe Abracrini.
Keywords: FISH; Orthoptera; constitutive heterochromatin; fluorochromes; ribosomal DNA.