First report on C-banding and fluorescent banding in species of Dieuches (Rhyparochrominae: Lygaeidae: Heteroptera)

Although the karyotypes of twelve species of Dieuches Dohrn, 1860 belonging to Rhyparochrominae have been described so far, there is no information about heterochromatin and its characterization in terms of base composition for any of the species. In the present paper, C-banding and fluorescent banding have been applied for the first time to three species of Dieuches : D. uniguttatus, D. insignis (2n = 12 = 8A + 2m + XY) and D. coloratus (2n = 14 = 10A + 2m + XY). Dieuches uniguttatus and D. insignis show distinct terminal C-bands along with a few interstitial bands in all the autosomal bivalents, whereas in D. coloratus , one autosomal pair is almost completely heterochromatic, three show C-positive bands while one is totally euchromatic. The sex chromosomes too show heterogeneity in distribution of C-heterochromatin among three Dieuches species. Characterization of heterochromatin in D. uniguttatus and D. insignis using DAPI/CMA₃ staining reveals that in D. uniguttatus , C- heterochromatin blocks of all the autosomal bivalents, which are predominantly A–T rich, whereas in D. insignis , these are rich both in A–T and G–C. In D. uniguttatus, sex chromosomes X and Y have localized G–C rich regions whereas in D. insignis , these are scattered in X and absent in Y. As variations in the heterochromatin represent the main source of karyological differentiation among and within species, it seems that there occurred extensive redistribution of heterochromatin within the complement as the three species evolved. There is need for cytological details of more species to understand evolutionary aspects in the genus Dieuches .