Glyphosate (GLY) is the most used herbicide worldwide and its effects on anurans are well known. Pollutants can cause physiological and morphological effects. Therefore, this study evaluated the effects of GLY on hepatic melanomacrophages as a response to environmental stressors. Three treatments were exposed to different concentrations of pure GLY (100, 1000, and 10,000 μg g(-1), respectively), and there was also a control group. After the experimental time, liver and blood were analyzed. Melanomacrophages (MMCs) were located between the hepatocyte cordons, close to sinusoids. GLY increased the melanin area in MMCs of Leptodactylus latinasus exposed since lowest concentration until highest concentration. GLY also changed the occurrence of hepatic catabolism pigments into melanomacrophages and erythrocyte nuclear abnormalities; therefore, it can interfere with the hepatic metabolism. In conclusion, GLY promotes alterations in the hepatic tissue and erythrocyte nuclear abnormalities. Furthermore, MMCs may be useful as morphological responses of GLY effects.
The purpose of this study was to evaluate the impact of acid mine drainage on the chemistry and the macrobenthos of the Carolina stream (San Luis - Argentina). Samples were obtained in the years 1997-1998 at two sites: site C(1), located 200 m upstream of the drainage, and site C(2), located 800 m downstream. The system buffer capacity was evaluated in the non - contaminated site by means of the buffer index calculation. The physico - chemical changes observed as a consequence of the contribution of acid mine drainage (AMD) were: a decreasing of pH and an increase in the ionic concentration, especially sulfate and Fe coming from the oxidation produced by chemiolithotrophic bacteria. The values obtained indicated a low buffer capacity and a high intrinsic vulnerability of the system to resist the impact originated by the AMD, producing a remarkable decreasing of pH of the receiving stream. These changes caused modifications in the original benthic community that was replaced by organisms more tolerant to the acid stress. A reduction in the abundance and in the taxonomic richness of the benthic macroinvertebrates was observed when compared with the reference station. An increase in the proportion of Chironomidae and of Acari and a decrease in the proportion of the remaining taxa were observed. The most sensitive groups were Ephemeroptera, Trichoptera and Mollusca. The community was mostly affected by the following variables: pH, conductivity, sulfate and dissolved total Fe.
Benthic macroinvertebrate tolerance to water acidity in the Grande river sub-basin (San Luis, Argentina)Acidic stress induces multiple adverse effects on the benthic macroinvertebrate community. The methods used to assess the taxa tolerance limit are based on qualitative relations between species at different pH values. The aim of this work was to estimate the tolerance of benthic macroinvertebrates to water acidification. Four sampling stations were established in the sub-basin of the Grande River, three of them (G 1 , G 2 and G 3 ) on the Grande River and one (C) in one of its tributaries, the Carolina Stream, which receives the acid drainage of an abandoned gold mine. Sample collection (n = 24) was carried out with a Surber net and recorded bimonthly between May 1997 and December 1998. The tolerance limit (TL), the optimal pH, the tolerance range (TR) and the acidification index (AI) were calculated for each taxon. pH values ranged between 3.6 and 9.6. Sixty eight taxa were identified and separated into three groups, according to the TL: > 5.5 with 50 %, an intermediate group with a value of 5.5 and the remaining ones (40 %) with values < 4.7. Several acid-sensitive taxa were not present in station C. Dipterans presented higher tolerance to acidity. The application of the acidification index (AI) resulted in category 1 (not acidified) in G 1 , G 2, and G 3 and in category 0.5 (acidity episodes) in C.
Aim: The use of biological indicators of pollution has increased in recent years as an alternative to the monitoring of water quality. Phytoplankton community selectively respond to different anthropogenic disturbances, such as water dams and the increase of nutrients coming from city centers, which leads to the eutrophication of the aquatic environment. The objective of this work was to evaluate the composition and the structure of the algal and Cyanobacterial communities in order to prove human influences by the presence of reservoirs with some degree of eutrophication and the impact of urbanization in two rivers at the Bebedero basin in San Luis province (Argentine). Methods: Four sites were sampled: two of them were placed before dams and villages (V 1 ) and (P 1 ) and two after them (V 2 ) and (P 2 ). Each site was visited in every season of the year: summer, autumn, winter and spring. Qualitative and semi-quantitative phytoplankton samples were taken, and the frequency of occurrence was determined. Variations between pairs of sampling stations were analyzed through the Jaccard similarity and complementarity indices. Results: Ninety two taxa were identified, of which diatoms were the most frequent. The most affected station was P 2 with high abundance, less diversity and equitability, whereas the species more tolerant to the presence of organic matter were Melosira varians, Navicula tripunctata, Oscillatoria limosa, Gomphonema parvulum and Coelastrum microporum, and some species of euglenophytas. Conclusion: Therefore, the structure and composition of the algal and Cyanobacterial communities allowed us to identify sections more sensitive to human-induced alterations.Keywords: biological quality, algal communities, urbanization effect, regulated streams.Resumo: Objetivo: O uso de indicadores biológicos de poluição tem aumentado nos últimos anos como alternativa de monitoramento da qualidade da água. A comunidade fitoplanctônica responde seletivamente a diferentes perturbações antrópicas, como construção de barragens e aumento dos nutrientes em centros urbanos que levam à eutrofização de ambientes aquáticos. O objetivo deste trabalho foi avaliar a composição e a estrutura das comunidades de algas e cianobactérias, a fim de comprovar a influência humana através da presença de reservatórios com algum grau de eutrofização e do impacto da urbanização em dois rios na bacia do Bebedero da província de San Luis (Argentina). Métodos: Quatro estações de coleta foram selecionados: duas antes dos reservatórios e aldeias (V1) e (P1) e duas após os mesmos (P2) e (V2). Cada estação foi visitada quatro vezes durante um ciclo anual: verão, outono, inverno e primavera. Foram coletadas amostras quantitativas e semiquantitativas do fitoplâncton e foi determinada a frequência de ocorrência. Foram analisados o grau de semelhança entre pares de estações de coleta, utilizando o índice de similaridade de Jaccard e índice de complementaridade. Resultados: Foram identificados 92 táxons, sendo mais frequente as diatomáceas. P...
Distribution of Baetodes huaico extends up to the Province of San Luis (Argentina). This constitutes the southernmost record of this species. Morphologicla characteristics were used for the species recognition.
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