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The aim of this paper is to report 10 predation events of anuran amphibians by giant water bugs of the genus Lethocerus in different localities in northeastern Argentina. With the exception of Scinax fuscovarius and Physalaemus biligonigerus, they are all new records of adult anurans being prey to these invertebrates. We conclude that this interaction is of extremely importance in the regulation of amphibian populations and should be studied in a thorough manner.

The anuran species group Physalaemus gracilis comprises six species, and variation in the location of nucleolus organizer regions (NORs) was observed across the four species that have been karyotyped to date. The NORs are located interstitially on chromosome 8 of P. carrizorum Cardozo et Pereyra, 2018, and P. lisei Braun et Braun, 1977, terminally on chromosome 8 of P. gracilis (Boulenger, 1883), and terminally on chromosome 10 of P. barrioi Bokermann, 1967. To contribute to the comparative analysis of this group, including the assessment of the hypothesis of homology among these NOR-bearing chromosomes, we described the karyotype of P. evangelistai Bokermann, 1967, and expanded the cytogenetic analyses of P. carrizorum , P. lisei , and P. barrioi . We used classical cytogenetic techniques and mapped, by fluorescent in situ hybridization (FISH), two repetitive sequences: the PcP190 satellite DNA and the U2 snRNA gene. Physalaemus evangelistai exhibited a 2n = 22 karyotype, with meta- and submetacentric chromosomes, which corresponds to the typical karyotypic configuration of the genus. We found an interstitial heterochromatin DAPI-positive band on the short arm of the NOR-bearing chromosomes 8 of P. evangelistai and P. carrizorum from Palmas-PR, and chromosome 10 of P. barrioi , which corroborates the hypothesis that these chromosomes are homologous. In P. evangelistai , an additional NOR was observed on chromosome 9 of females. Moreover, the karyotype of P. carrizorum from Palmas-PR differed from that previously described for P. carrizorum from Misiones, particularly in the number of PcP190 clusters and intrachromosomal position of the NOR on chromosome 8. Specimens from Palmas-PR showed a terminal NOR on chromosome 8 and PcP190 clusters on chromosomes 1 and 3, whereas those from Misiones had an interstitial/pericentromeric NOR on chromosome 8 and a single PcP190 cluster on chromosome 3. Further analyses are still needed to assess whether these cytogenetic differences represent interspecific variation.

The genus Atelognathus is composed of five species that occur in the southernmost regions of Argentina and Chile. It belongs to the Batrachylidae, one of the few endemic anuran families from Patagonia. More than 50 yr ago, it was concluded that A. reverberii had a diploid chromosomal complement of 2N = 26, a feature later reported for other congenerics. In this work, we describe the cytogenetics of all known species of Atelognathus (A. nitoi, A. patagonicus, A. praebasalticus, A. reverberii, and A. solitarius) and two additional undetermined populations. Unexpectedly, our analyses showed that all have a diploid chromosomal complement 2N = 24, which contrasts with conclusions of previous studies. We conclude that a karyotype of 2N = 24 is shared in Atelognathus as a derived condition within Batrachylidae. Additionally, we describe and discuss other cytogenetics characters (i.e., nucleolar organizer region location and C-banding patterns) of Atelognathus and related genera of Batrachylidae in an evolutionary framework.

Recently, Physalaemus albifrons (Spix, 1824) was relocated from the Physalaemus cuvieri group to the same group as Physalaemus biligonigerus (Cope, 1861), Physalaemus marmoratus (Reinhardt & Lütken, 1862) and Physalaemus santafecinus Barrio, 1965. To contribute to the analysis of this proposition, we studied the karyotypes of Physalaemus albifrons, Physalaemus santafecinus and three species of the Physalaemus cuvieri group. The karyotype of Physalaemus santafecinus was found to be very similar to those of Physalaemus biligonigerus and Physalaemus marmoratus, which were previously described. A remarkable characteristic that these three species share is a conspicuous C-band that extends from the pericentromeric region almost to the telomere in the short arm of chromosome 3. This characteristic is not present in the Physalaemus albifrons karyotype and could be a synapomorphy of Physalaemus biligonigerus, Physalaemus marmoratus and Physalaemus santafecinus. The karyotype of Physalaemus santafecinus is also similar to those of Physalaemus marmoratus and Physalaemus biligonigerus owing to the presence of several terminal C-bands and the distal localization of the NOR in a small metacentric chromosome. In contrast, the Physalaemus albifrons karyotype has no terminal C-bands and its NOR is located interstitially in the long arm of submetacentric chromosome 8. The NOR-bearing chromosome of Physalaemus albifrons very closely resembles those found in Physalaemus albonotatus (Steindachner, 1864), Physalaemus cuqui Lobo, 1993 and some populations of Physalaemus cuvieri Fitzinger, 1826. Additionally, the Physalaemus albifrons karyotype has an interstitial C-band in chromosome 5 that has been exclusively observed in species of the Physalaemus cuvieri group. Therefore, we were not able to identify any chromosomal feature that supports the reallocation of Physalaemus albifrons.

Fil: Ferro, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina

Previous studies of DNA sequence and karyotypic data have revealed high genetic diversity in the Physalaemus cuvieri – Physalaemus ephippifer species complex—a group of small leptodactylid frogs in South America. To date, seven major genetic lineages have been recognized in this group, with species delimitation tests supporting four to seven of them as valid species. Among these, only P. ephippifer shows heteromorphic sex chromosomes, but the implications of cytogenetic divergence for the evolution of this group are unknown. We analyzed karyotypic, mitochondrial DNA, and 3RAD genomic data to characterize a putative contact zone between P. ephippifer and P. cuvieri Lineage 1, finding evidence for admixture and karyotypic evolution. We also describe preliminary evidence for admixture between two other members of this species complex—Lineage 1 and Lineage 3 of P. cuvieri . Our study sheds new light on evolutionary relationships in the P. cuvieri – P. ephippifer species complex, suggesting an important role of karyotypic divergence in its evolutionary history and underscoring the importance of hybridization as a mechanism of sex chromosome evolution in amphibians.

Fil: Ferro, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina

The genus Akodon Meyen, 1833 is one of the most species-rich among sigmodontine rodents and has great chromosome variability. Akodon montensis has a relatively broad distribution in South America, and Argentine populations are located in the southernmost region of its range. Brazilian populations have important chromosomal variability, but cytogenetic data from Argentina are scarce. We performed a chromosome characterization of natural populations of Akodon montensis using conventional staining, C-banding, Ag-NORs and base-specific fluorochromes. A total of 31 specimens from five localities of Misiones Province, in Argentina, were analyzed. The 2n=24 chromosomes was the most frequently observed karyotype. However, five individuals presented 25 chromosomes due to a supernumerary B-chromosome; and one individual had 2n=26 due to one B plus a trisomy for chromosome 11. Additionally, two XY females and two variants of the X chromosomes were found. C-positive centromeric bands occurred in all chromosomes; additional C-bands were observed in some autosomes, the X, Y and B chromosomes. Ag-NORs were observed in five autosomes, and the B chromosome was frequently marked. Fluorochrome banding was similar among karyotypes of the analyzed populations. Comparisons of cytogenetic data among populations of Argentina and Brazil showed the presence of high intraspecific variability in Akodon montensis and some differences among regions.

Fil: Barrasso, Diego Andrés. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Diversidad y Evolución Austral; Argentina

Fil: Boeris, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentina. Universidad Nacional de Misiones; Argentina