>b<Alterações morfológicas em tecidos linfoide e endócrino de anuros sujeitos à contaminação ambiental em áreas cultivadas no estado do Ceará>/b<

Abstract

The amphibians are fascinating Vertebrata that live a "double life": because they share development stages in terrestrial and aquatic environments, and for their physiological and immunological sensibility to external stressors, they are considered bioindicators of environmental balance. The order Anura comprises the most significant number of species and has been widely employed in biomonitoring. In the Brazilian semiarid region, the Jaguaribe River is a prominent source threatened by poor management of its uses and the chemical contamination risk associated with irrigated agriculture. The objective of this work was to evaluate morphological biomarkers and to measure potentially toxic chemical elements in tissue samples of Leptodactylus macrosternum (Anura: Leptodactylidae), a native, abundant and widely distributed anuran, in order to apply them as a biomonitoring tool in Lower Jaguaribe Valley River agrosystems, northeastern Brazil. For this purpose, one hundred and twenty specimens were collected in cultivated and non-cultivated areas from Tabuleiro do Norte municipality from May to June/2017. The ICP-MS technique quantified potentially toxic elements in carcasses' dry samples, while lymphoid and endocrine morphological alterations were investigated through post morten examination and histopathology. As, Cd, Cr, Co, Cu, Fe, Mn, Ni, Pb and Zn were detected in the samples. Predominant lesions were classified in degenerative (41,0%), followed by proliferative (23,3%), inflammatory (17,2%) and circulatory (14,4%). Nodular colloid goiter, granulocytic infiltration, hyperplasia and vacuolar degeneration were the most significant observed alterations in thyroids, parathyroids, pancreatic islets and interrenal glands, respectively. Epithelial hyperplasia and periarteriolar lymphocytic sheaths atrophy were the predominant changes seen in the thymus and spleen, respectively. The frequencies of parenchymal cytolysis with heterophilic infiltration in parathyroids, most thymus lesions, and splenic heterophilic infiltration were significantly higher in cultivated areas (p<0,05). Cu, Mn and Zn concentrations showed superior to those measured in another northeastern congener species. Most likely come from two different origins, Co, Zn, Fe, and Pb 13 influenced most examined individuals. Although significantly different concentrations were not observed between the areas, the element As tended to get higher concentrations in cultivated, while Pb showed it in non-cultivated areas. Multivariate statistic tests revealed that potentially toxic inorganic compounds significantly influenced the histology alterations, mainly the pancreatic islets vacuolization and splenic stromal hyperplasia. The quantified chemical elements explained 60,2% of the data variance, bringing out other factors (habitat fragmentation, higher temperatures and ultraviolet radiation, lower rainfalls, organic contaminants, human presence stressors and others). The current findings suggested L. macrosternum as a virtually environmental bioindicator of chemical c...