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Defensive behavior is an important mechanism for the survival of organisms, and understanding the different strategies improves our knowledge regarding prey-predator relationships. Herein, based on field observation, we describe a sequence of behaviors displayed by the South American pond snake Pseudoeryxplicatilis from the Pantanal floodplains in midwestern Brazil. The individual displayed a repertoire of five different defensive behaviors, without an evident sequence pattern recognized. Two of the displays are new for the species, and one for the tribe. The new defensive repertory described may suggest animals oriented by vision as main predators of P. plicatilis. [ABSTRACT FROM AUTHOR]

A new species of frog of the genus Odontophrynus is described from grassland of the subtropical regions of Argentina, Brazil, and Paraguay based on morphological, osteological, bioacoustical, cytogenetic, and molecular evidence. The new species is characterized by having medium size; rostral and eye-nostril glandular warts well developed; several long glandular ridges, longitudinally oriented, on dorsum; several medium-sized, nearly rounded, dark-brown dorsal blotches; light mid-dorsal stripe continuous and well defined or restricted to the head and the urostyle regions; and mid-dorsal stripe, interorbital, and dorsolateral bands with a moderately whitish highlight, light brown, or reddish coloration. Additionally, the new species has a skull with nasals slightly separated both from each other and frontoparietals, and frontoparietal fontanelle not exposed. The advertisement call consists of a single multipulsed note with a dominant frequency of 820-1,121 Hz and a pulse rate of 99.3-140.7 pulses/s. The chromosomal complement is diploid with 2N = 2X = 22 chromosomes and nucleolar organizer regions on the interstitial regions of the short arm of chromosome pair 4. The phylogenetic analysis allowed us to recover the new species belonging to the O. americanus species group with genetic distances from its congeners ranging from 2.11 to 4.82% in a partial sequence of 16S ribosomal RNA gene. The new species is geographically isolated from the other currently known diploid species of the group, but in some localities is found in sympatry or syntopy with the tetraploid O. americanus. [ABSTRACT FROM AUTHOR]

Herein, we provide the first comprehensive amphibian checklist for the State of Tocantins, North of Brazil, based on field sampling, literature data, and specimens deposited in zoological collections. We performed field surveys from 2012 to 2019 in 12 Tocantins municipalities, totaling 376 days of sampling effort. We analyzed 25 papers from the literature and examined 1311 specimens from collections and collected 750 during field surveys. We recorded 90 amphibian species distributed in 12 anurans and two caecilians families. At least seven undescribed species along the state were recorded. We also present new records for 20 species for the state, nine of them corresponding to Amazonian species, four Cerrado endemic, one Caatinga species, and the widely distributed treefrog Boana crepitans; the others five new records comprise undescribed species. Our data also suggest that the Tocantins amphibian composition is not geographically structured in relation to the biomes, since Amazonian, Caatinga, and Cerrado amphibian lineages have their distribution nearly completely overlapped in the state. We propose that this absence of spatial structuration may be a result of two factors (synergetic or not). First, the events of expansion and retraction of the biomes caused by the Quaternary climatic cycles, which may have mixed the populations of species from different biomes causing the notable pattern of overlapped distribution observed here. Second, the forest environments (e.g. gallery and riparian forests) associated to the Araguaia-Tocantins River basins may have acted as historical dispersal corridors for the Amazonian amphibian lineages into the Cerrado of the Tocantins. Despite the sampling effort of the present study, we stress that gaps of information still remain and further field sampling efforts should be performed along the state. Lastly, taxonomic appraisals involving the species with problematic taxonomic status recorded here should be based on multiples lines of evidences (acoustic, molecular, and morphological data), which will render a more accurate view on the Tocantins amphibian diversity. Such data are extremely necessary under the current high rate of habitat loss across the state, since they can be used to guide public policies of conservation. [ABSTRACT FROM AUTHOR]