Diet of tadpoles of Physalaemus biligonigerus (Leiuperidae) from agricultural ponds in the central region of Argentina

The intensification of agriculture has led an important loss of natural habitats, with significant consequences for biodiversity. In this sense, the studies on anuran amphibian tadpoles inhabiting these environments are relevant, because the larval stage is a phase of population regulation. The aim of this study was to analyze the diet in Physalaemus biligonigerus tadpoles, an anuran species widely distributed in South America and that inhabit agroecosystems. Three sites were sampled; two agroecosystems with different alteration degrees (AG1 and AG2) and an uncultured (SM) third place. The captured tadpoles were anesthetized, fixed and preserved in formaldehyde (10%). Subsequently, the complete intestine was removed and analyzed for food items under a binocular microscope. The diet in P. biligonigerus tadpoles has a dominance of algae Bacillariophyceae, mainly in agroecosystems, due to the presence of the genera Navicula, Nitzschia and Gomphonema. There was a considerable abundance of the Gomphonema genus in the AG2 site. In addition, in the AG1 site several non-diatom algae were particularly abundant in the diet, such as the genera Euglena, Oedogonium and Chaetophora. In the SM site, the non-diatom genus Oscillatoria was well represented in the diet. Tadpoles inhabiting the site with abundant crop and livestock (AG1) ingested a significantly smaller amount of food. The presence of certain algae associated with eutrophic environments could indicate some pollution in agroecosystems (AG1 and AG2). Larval diet is suggested as a potential bioindicator of environmental health for these areas

Impact assessment of agriculture and livestock over age, longevity and growth of populations of common toad Rhinella arenarum (anura: Bufonidae), central area of Argentina

The central area of Argentina has been greatly affected mainly due to urbanization and intensive agriculture (corn, soybean and cattle). Age, longevity and growth were determined in populations of the common toad, Rhinella arenarum, from urban and agricultural sites in the central area of Argentina. Five sites in Rio Cuarto (33º05′52.95″ S - 64º26′02.99″ W, 471 m a.s.l.; Córdoba Province, Argentina) with different degree of anthropic disturbance were selected to evaluate the impact of urbanization and agriculture on common toad populations as sentinel species. The selected sites were chosen according to intensive to moderate agricultural and livestock activity, low influence of agricultural and an intensive to moderate urban influence. A total of 114 adults (males and females) were sampled. Skeletochronology was used to estimate toad's growth and age, which relies on the analysis of the annual Lines of Arrested Growth or LAGs in bones. Size, age and growth reductions occurrence in intensive agricultural systems could suggest long term impacts on fitness. In addition, intensive urban activity also affects life history of the population of R. arenarum, although to a lesser extent than the agricultural-livestock activity. Keywords: Rhinella arenarum toad, Agriculture, Urbanization, Skeletochronology, Age, von Bertalanffy mode

Age structure, growth and longevity in the common toad, Rhinella arenarum, from Argentina

Age structure, growth and longevity was determined in the common toad, Rhinella arenarum, from a suburban pond located in the Pampa plains, central Argentina during two breeding seasons, in 2000 and 2008 by using skeletochronology, which relies on the analysis of the annual lines of arrested growth (LAGs) in bones. Both females and males were captured in 2008, while only males were recorded in 2000. Females were significantly larger than males. Mean population age was 2.4 ± 0.9 years in 2000. In 2008, the difference in age was not significant between the sexes (Males: 3.0 ± 0.7, n = 21; Females: 2.6 ± 0.9, n = 12), neither between males in 2000 and 2008. The longevity in males of 2000 was 6 LAGs and exceeded that of males (5 LAGs) and females (4 LAGs) in 2008. Von Bertalanffy curves showed that the growth coefficient in the males of 2000 (K = 2.97 ± 0.47) was almost double that of females (K = 1.21 ± 0.10) and males (K = 1.01 ± 0.14) of 2008. Males and females Rhinella arenarum show different morphological and life history traits and the year of sampling can significantly influence the estimation of the studied parameters such as age at maturity and growth rates

Age structure, growth and longevity in the common toad, <em>Rhinella arenarum</em>, from Argentina

<p>Age structure, growth and longevity was determined in the common toad, <em>Rhinella arenarum</em>, from a suburban pond located in the Pampa plains, central Argentina during two breeding seasons, in 2000 and 2008 by using skeletochronology, which relies on the analysis of the annual lines of arrested growth (LAGs) in bones. Both females and males were captured in 2008, while only males were recorded in 2000. Females were significantly larger than males. Mean population age was 2.4 ± 0.9 years in 2000. In 2008, the difference in age was not significant between the sexes (Males: 3.0 ± 0.7, n = 21; Females: 2.6 ± 0.9, n = 12), neither between males in 2000 and 2008. The longevity in males of 2000 was 6 LAGs and exceeded that of males (5 LAGs) and females (4 LAGs) in 2008. Von Bertalanffy curves showed that the growth coefficient in the males of 2000 (K = 2.97 ± 0.47) was almost double that of females (K = 1.21 ± 0.10) and males (K = 1.01 ± 0.14) of 2008. Males and females <em>Rhinella arenarum</em> show different morphological and life history traits and the year of sampling can significantly influence the estimation of the studied parameters such as age at maturity and growth rates.</p

Diet of tadpoles of <em>Physalaemus biligonigerus</em> (Leiuperidae) from agricultural ponds in the central region of Argentina

The intensification of agriculture has led an important loss of natural habitats, with significant consequences for biodiversity. In this sense, the studies on anuran amphibian tadpoles inhabiting these environments are relevant, because the larval stage is a phase of population regulation. The aim of this study was to analyze the diet in <em>Physalaemus biligonigerus</em> tadpoles, an anuran species widely distributed in South America and that inhabit agroecosystems. Three sites were sampled; two agroecosystems with different alteration degrees (AG1 and AG2) and an uncultured (SM) third place. The captured tadpoles were anesthetized, fixed and preserved in formaldehyde (10%). Subsequently, the complete intestine was removed and analyzed for food items under a binocular microscope. The diet in <em>P</em>. <em>biligonigerus</em> tadpoles has a dominance of algae Bacillariophyceae, mainly in agroecosystems, due to the presence of the genera <em>Navicula</em>, <em>Nitzschia</em> and <em>Gomphonema</em>. There was a considerable abundance of the <em>Gomphonema</em> genus in the AG2 site. In addition, in the AG1 site several non-diatom algae were particularly abundant in the diet, such as the genera <em>Euglena</em>, <em>Oedogonium</em> and <em>Chaetophora</em>. In the SM site, the non-diatom genus <em>Oscillatoria</em> was well represented in the diet. Tadpoles inhabiting the site with abundant crop and livestock (AG1) ingested a significantly smaller amount of food. The presence of certain algae associated with eutrophic environments could indicate some pollution in agroecosystems (AG1 and AG2). Larval diet is suggested as a potential bioindicator of environmental health for these areas