Diplopods as Soil Bioindicators of Toxicity After Application of Residues From Sewage Treatment Plants and Ethanol Industry.

Residues like sewage sludge and vinasse have been reused as agricultural fertilizers, but they also present a potential to contaminate soils. Diplopods have been considered excellent bioindicators of soil contamination. In the present study, Rhinocricus padbergi were used to assess toxicity in samples of sewage sludge, biosolids, and sugarcane vinasse. The behavioral analysis, mortality rate, and histological, histochemical, and ultrastructural analyses of the midgut of diplopods were the parameters evaluated. Behaviorally, some diplopods avoided burying themselves after 30 days in soil with biosolid or vinasse. Besides, certain residue combinations were able to cause death of all individuals between 60 and 90 days of exposure. The main tissue responses were significant brush border thickening, induction of epithelial renovation, clustering of hemocytes, accumulation of cytoplasmic granules in hepatic cells, hepatic cells with heteropycnotic nuclei, and cytoplasmic degradation. Alterations were observed at various levels among treatments with different samples and exposure times. Ultrastructural analysis revealed elongation of microvilli coated with a layer of an amorphous substance, resulting in a thicker brush border as observed in the histological analysis. After 30 days of exposure, animals showed an accumulation of spherocrystals in hepatic cells and high absorption of substances, based on the elongation of microvilli. Results obtained in the chemical analysis and the behaviors observed in diplopods suggest that animals processed the residues. Therefore, caution should be exercised in the disposal of these residues in agriculture.

Sugar cane vinasse in water bodies: impact assessed by liver histopathology in tilapia.

Aquatic ecosystems are the main receptors of toxic substances from human activities. With the increase in sugar cane production, vinasse - the main residue of ethanol production - is a potential contaminant of water resources, due to its high organic matter content. This study was aimed at evaluating the toxicity of vinasse by examining the liver of the fish Oreochromis niloticus exposed to different dilutions of sugar cane vinasse (1%, 2%, 5%, 5% and 10%) in laboratory bioassays. Portions of liver were collected and fixed for histological and histochemical techniques to detect total proteins, polysaccharides and lipids. In the histological analysis, the groups treated with vinasse exhibited significant alterations, such as loss of cytoplasmic integrity, loss of cell limit and tissue disorganization. Protein and lipid profiles were not altered. Higher accumulation of polysaccharides was detected in fish exposed to lower concentrations of vinasse, with a gradual decrease in animals treated with vinasse in higher concentrations. We concluded that vinasse has a dose-dependent toxic and cytotoxic potential in water bodies and that the liver is strongly affected when acutely exposed to this contaminant.