title: Cytogenetic characterization and B chromosome diversity in direct-developing frogs of the genus Oreobates (Brachycephaloidea, Craugastoridae).
abstract: Oreobates Jiménez de la Espada, 1872 is a large group of South American frogs with terrestrial reproduction and direct development, located in the superfamily Brachycephaloidea. About 260 brachycephaloidean species have been cytogenetically studied so far, at least with standard techniques. However, this information represents fewer than 17% species of the family Craugastoridae Hedges, Duellman & Heinicke, 2008, where the genus Oreobates is included. In the present work, using a diversity of standard and molecular techniques, we describe the karyotype of Oreobates barituensis Vaira & Ferrari, 2008, Oreobates berdemenos Pereyra, Cardozo, Baldo & Baldo, 2014 and Oreobates discoidalis (Peracca, 1895), from northwestern Argentina. The three species analyzed showed a diploid karyotype with 2n = 22 biarmed chromosomes, fundamental number (FN) = 44, nucleolus organizer regions (NORs) located pericentromerically on pair 7, and a centromeric and pericentromeric C-banding pattern. We observed variations in the chromosome number in Oreobates barituensis due the presence of two morphs of B chromosomes, one medium-sized telocentric (BT) and another subtelocentric and smaller (Bst). Both B chromosomes are mitotically stable and were recorded in all somatic and germinal cells analyzed. The BT chromosome occurred at a maximum of one per individual (2n = 22+BT), and the other one was observed single (2n = 22 + Bst) or as a pair in two doses (2n = 22 + 2BT). We additionally observed other supernumerary chromosomes in the three species analyzed, all of them euchromatic, small, dot-shaped and with instability during mitoses, showing a frequency of occurrence below 50% in studied specimens. The occurrence of polymorphic and spontaneous chromosomal rearrangements and supernumerary chromosomes is a recurrent feature reported in frogs with terrestrial habits (Brachycephaloidea and Hemiphractidae Peters, 1862), which suggests that Brachycephaloidea may be a promising group for studying the origin and maintenance of B chromosomes in anurans.
authors.affiliation: Laboratorio de Genética Evolutiva, Instituto de Biología Subtropical (CONICET-UNaM), Facultad de Ciencias Exactas Químicas y Naturales, Universidad Nacional de Misiones; Félix de Azara 1552, CPA N3300LQF Posadas, Argentina.
authors.forename: Juan Martín
authors.initials: JM
authors.lastname: Ferro
authors.affiliation: Laboratorio de Genética Evolutiva, Instituto de Biología Subtropical (CONICET-UNaM), Facultad de Ciencias Exactas Químicas y Naturales, Universidad Nacional de Misiones; Félix de Azara 1552, CPA N3300LQF Posadas, Argentina.
authors.forename: Alberto
authors.initials: A
authors.lastname: Taffarel
authors.affiliation: Laboratorio de Genética Evolutiva, Instituto de Biología Subtropical (CONICET-UNaM), Facultad de Ciencias Exactas Químicas y Naturales, Universidad Nacional de Misiones; Félix de Azara 1552, CPA N3300LQF Posadas, Argentina.
authors.forename: Darío
authors.initials: D
authors.lastname: Cardozo
authors.affiliation: Fundación Miguel Lillo, Instituto de Herpetología; Miguel Lillo 251, CP 4000, San Miguel de Tucumán, Tucumán.
authors.forename: Jimena
authors.initials: J
authors.lastname: Grosso
authors.affiliation: Universidad Nacional de Salta (UNSa), Avenida Bolivia 5150, Salta, Argentina.
authors.forename: María Pía
authors.initials: MP
authors.lastname: Puig
authors.affiliation: Laboratório de Citogenética, Instituto de Ciências Biológicas, Universidade Federal do Pará,Tv. Augusto Correia 1, CEP 66075-900, Belém, Pará, Brazil.
authors.forename: Pablo
authors.initials: P
authors.lastname: Suárez
authors.affiliation: Centro de Investigaciones y Transferencia de Jujuy (CIT-JUJUY), CONICET-UNJu, Av. Bolivia 1711 (4600), San Salvador de Jujuy, Argentina.
authors.forename: Mauricio Sebastián
authors.initials: MS
authors.lastname: Akmentins
authors.affiliation: Laboratorio de Genética Evolutiva, Instituto de Biología Subtropical (CONICET-UNaM), Facultad de Ciencias Exactas Químicas y Naturales, Universidad Nacional de Misiones; Félix de Azara 1552, CPA N3300LQF Posadas, Argentina.
authors.forename: Diego
authors.initials: D
authors.lastname: Baldo
keywords: Anura; Cytogenetics; accessory elements; ribosomal DNA