Nucleolar organizer regions in Sittasomus griseicapillus and Lepidocolaptes angustirostris (Aves, Dendrocolaptidae): evidence of a chromosome inversion

cytogenetic studies in birds are still scarce compared to other vertebrates. woodcreepers (dendrocolaptidae) are part of a highly specialized group within the suboscines of the new world. they are forest birds exclusive to the neotropical region and similar to woodpeckers, at a comparable evolutionary stage. this paper describes for the first time the karyotypes of the olivaceous and the narrow-billed woodcreeper using conventional staining with giemsa and silver nitrate staining of the nucleolar organizer regions (ag-nors). metaphases were obtained by fibular bone marrow culture. the chromosome number of the olivaceous woodcreeper was 2n = 82 and of the narrow-billed woodcreeper, 2n = 82. ag-nors in the largest macrochromosome pair and evidence of a chromosome inversion are described herein for the first time for this group.