Feeding ecology is one of the most important aspects in the life history of snakes; however, studies about their trophic ecology are scarce and sometimes inaccurate. Liophis poecylogyrus is a medium-sized snake distributed widely in South America and relatively abundant in the study area. We describe the diet and sexual dimorphism of L. poecilogyrus from northeast Argentina based on the examination of museum specimens, and we compare our data with studies that include representative samples of this species. Amphibians were the most frequent prey (75%), but only one reptile was found (1%). Families represented were: Bufonidae (53%), Leiuperidae (19%), Leptodactylidae (14%), Hylidae (7%), Cycloramphidae (3%), Microhylidae (2%), and Gymnophthalmidae (2%). We observed that L. poecilogyrus has significant sexual size dimorphism in all morphometric characters analyzed but not in scalation variables. Despite the fact that L. poecilogyrus is considered by some to be an omni-carnivore, our data and other quantitative studies on distant populations from South America lead us to suggest that this species eats primarily anurans. The population studied has its own characteristics but retains similarities with geographically nearby and remote populations. This species is a specialist and its feeding habits seem to be conservative both in different populations of the same species and in phylogenetically related species. Sexual size dimorphism may be a common feature of the taxonomic group.

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Terrestrial environments surrounding aquatic resources are important and intensively used by semi-aquatic species. In the present work, terrestrial dispersal and nesting sites of the freshwater turtle Phrynops hilarii were analyzed in the floodplain of the Paraná River, using field data and variables obtained from remote sensing. A total of 112 turtles and 44 nests were recorded during road sampling for one year (covered a total of 786 km in 30 surveys). Individuals were at a mean distance of 171.45 m from water, with a negative correlation between number of turtles and distance from water bodies. No significant differences in distance of turtles from water were observed among seasons. Phrynops hilarii nested at a mean distance of 136.51 m from water, showing a negative correlation between number of nests and distance from water bodies. Mean elevation of nests relative to maximum level of water body nearest each record was 1.13 m. The correlation between number of nests and elevation of the nearest water body was positive and significant. The landscape surrounding wetlands is important for P. hilarii to complete the life cycle, as nesting is done in this environment. Our results show that the habitat selected for nesting and terrestrial dispersal was proportionally different from that available in the entire study area, with a higher proportion of wetlands, grasslands and forests.

The micronucleus test (MN) is a biomarker of non-destructive genotoxicity that allows chromosomal damage and other nuclear alterations (NA) to be detected. Phrynops hilarii is a freshwater chelonium that inhabits regions of central-northern Argentina. The main objective was to determine the presence of MN and other NA in erythrocytes of natural populations of P. hilarii comparing their frequencies between three sites, two anthropized and one of control (cities of Diamante and Paraná) of Entre Ríos, Argentina, during the period 2015-2016. Eighteen individuals (six per sampling site) were evaluated at the sites: 1- PD: Pre-Delta National Park (control), 2- AG: Salto Ander Egg (agroecosystem) and 3- SU: Caleta Club Náutico (urban system). Blood was obtained from the femoral vein. The samples were stained with the May Grünwald-Giemsa method and observed under a microscope with an immersion objective. Micronucleus (MNF) and nuclear alterations (NAF) frequencies were determined every 1000 erythrocytes observed. A significant difference (p<0.05) was found between the PD site and the other sites (AG and SU), both for MNF (p=0.0021) and for NAF (p=0.0011). The highest frequency values ​​corresponded to the AG site (MNF: 3.33 ± 0.62; NAF: 4.67 ± 0.56). Finally, biomonitoring with P. hilarii was useful, so it could be considered as a bioindicator species to assess the quality of Argentina’s environments. Key words: Genotoxicity biomarkers, micronucleus test, nuclear alterations