Bioaccumulation, genotoxicity, and risks to native fish species from inorganic contaminants in the Pantanal Sul-Mato-Grossense, Brazil

The Aquidauana River is one of the most important rivers in the Pantanal region, Brazil. However, its waters have been contaminated by nearby anthropogenic activities, threatening native fish species. In this study, our objectives were: 1) to determine the concentrations of Al, As, Cd, Cu, Fe, Mn, Ni, Pb, and Zn in water and sediment samples from the Aquidauana River and to assess the risks posed to aquatic biota; 2) to quantify the concentration of these elements in muscle and liver tissue samples from four native fish species; 3) to evaluate the potential bioaccumulation of inorganic elements in the muscles and liver; and 4) to investigate genotoxicity biomarkers and their association with the inorganic element concentrations present in the muscle tissue. Water and fish samples were collected in November 2020. The concentrations of Al, As, Cd, Cu, Fe, and Pb in the water samples were in disagreement with the Brazilian legislation and presented risks to the aquatic biota. In terms of mixtures of inorganic elements, there was a great increase in the risk to biota. The As concentration did not meet the Brazilian standard for sediments in the sample collected at sampling site 6. The concentrations of Cd and Pb in the muscle tissue of Hypostomus regani, Prochilodus lineatus, Brycon hilarii, and Mylossoma duriventre exceeded the Brazilian standards for human consumption. H. regani showed greater genotoxic damage, and the higher the Al and Fe concentrations in the muscle tissue, the higher the frequencies of lobulated nuclei and nuclear invaginations. Together, our results demonstrate the negative impacts on native fish species from the Aquidauana River contamination and indicate risks to Pantanal biodiversity.

Acute Exposure to Biogenic Nanosilver Produced from Fusarium oxysporum in a Neotropical Fish

Biogenic nanosilver (bNAg) has emerged as a potentially less toxic alternative to synthetic nanosilver. However, no studies have evaluated its effects on a fish species from the Neotropical region. Thus, our aim was to evaluate the effects of a bNAg on the Neotropical fish Prochilodus lineatus. For this purpose, after 24 h of exposure to 100 µg L^-1 of bNAg, blood samples were collected to evaluate hematological, genotoxic, and plasma parameters. Gills and liver were sampled to evaluate biomarkers of oxidative stress and brain samples were used to assess neurotoxicity. The fish presented hyperglycemia, an increased number of erythrocytes, a reduction in antioxidant enzyme activity in both tissues evaluated, and a decrease in lipid peroxidation in the gills. We concluded that P. lineatus is a sensitive species to this nanoparticle, since it presented alterations in several biomarkers after an acute exposure.

Exposure to environmental concentrations of fipronil induces biochemical changes on a neotropical freshwater fish

Fipronil is a broad-use insecticide with severe toxicity to fish. Biomarkers responses and bioaccumulation were evaluated on Prochilodus lineatus after exposure to environmentally relevant concentrations of fipronil (0.5 μg L^-1, 9 μg L^-1, and 100 μg L^-1) in a prolonged flow-through assay and ex vivo gills short-term exposition. Lipid peroxidation (LPO), oxidatively modified proteins (PO), the activity of superoxide dismutase (SOD), the content of reduced glutathione (GSH), antioxidant capacity against peroxyles (ACAP), and acetylcholinesterase (AChE) were evaluated. Besides, levels of fipronil and metabolites were analyzed by GC-ECD. At the end of the flow-through assay, fipronil, Fp. sulfone and Fp. desulfinyl were detected in fish, being liver the target organ. Fipronil prolonged exposition promoted oxidative damage in lipids and proteins, alterations in the defense system and low-antioxidant capacity in organs of P. lineatus. The brain AChE activity was affected after prolonged exposition. Ex vivo gills exposition to fipronil promoted changes in antioxidant capacity and damage to lipids, providing a fast and suitable test to assess the pesticide exposure in fish. The results revealed that fipronil at environmental concentrations would be an inducer of oxidative stress in this fish, becoming a vulnerable species to the effects of fipronil in aquatic environments.

Biochemical and morphological biomarker responses in the gills of a Neotropical fish exposed to a new flavonoid metal-insecticide

The flavonoid metal-insecticide [Mg(hesp)₂(phen)], denominated MgHP, has high potential for controlling agricultural pests. If applied in large scale, it may reach aquatic ecosystems and be harmful to the biota. This study evaluated the effects of MgHP in the gills of the Neotropical fish, Prochilodus lineatus by determining the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione s-transferase (GST), and the levels of glutathione (GSH) and lipid peroxidation (LPO) after 24 and 96 h exposure to 0, 1, 10, 100 and 1000 μg L^-1. The histopathological changes with emphases to mitochondria-rich cells (MRC) were evaluated as well. After 24 h exposure the enzyme activities and the GSH and LPO levels were unchanged however, after 96 h exposure to high MgHP concentration (1000 μg L^-1), the GST activity and GSH levels increased. Oxidative stress measured as LPO levels did not occur after MgHP exposure in both periods. Gill tissue alterations increased after MgHP exposure to 10, 100 and 1000 μg L^-1. Cellular atrophy, pillar cells changes, filament epithelium hyperplasia and hypertrophy, lamellar epithelium hyperplasia were the most frequent histopathology. MRC in the filament epithelium decreased after exposure to 24 h and increased after 96 h indicating possible transitory osmo-ionic disruption. P. lineatus exhibited high tolerance to MgHP. The increased GST activity and GSH levels after 96 h exposure suggested possible MgHP accumulation and concentration- and time-dependent response. Histopathology in the gills of exposed fish occurred at high MgHP concentrations. These results suggested that the MgHP into water, at high concentrations, affect the gills by changing GST activity, GSH levels and histology being useful biomarkers for MgHP water contamination.

Diet-tissue discrimination factors (Δ(13) C and Δ(15) N) and turnover rate in somatic tissues of a neotropical detritivorous fish on C3 and C4 diets

In this study, diet-tissue discrimination factors and turnover rates were determined from the somatic tissues of a detritivorous fish Prochilodus lineatus. The carbon (Δ(13) C) and nitrogen (Δ(15) N) diet-tissue discrimination factors varied for all feed rations with a range of Δ(13) C values between -1·9 and 3·6‰ and Δ(15) N between 3·3 and 5·7‰. Carbon turnover rate in the blood was 23·1 days for the C3 ration and 34·7 days for the C4 ration, in the liver was 9·9 days under the C3 ration and nitrogen turnover rate was the same (23·1 days) in the liver for both C4 and C3 -C4 rations, and 13·9 days in the muscle for C3 -C4 ration.

Isolation and characterization of 20 polymorphic microsatellite loci in the migratory freshwater fish Leporinus obtusidens (Characiformes: Anostomidae) using 454 shotgun pyrosequencing

Twenty polymorphic microsatellite markers were developed for the Neotropical fish Leporinus obtusidens using a next generation sequencing approach and tested in two other characifomes species, Schizodon platae and Prochilodus lineatus. Microsatellite loci alleles in L. obtusidens ranged between 2 and 20 alleles per locus (mean = 5·7), with expected heterozygosity values ranging from 0·097 to 0·956 (mean = 0·578) and observed heterozygosity values ranging from 0·000 to 0·800 (mean = 0·400) in a sample of 20 specimens from the lower Paraná River (Argentina). Most of these markers will be a valuable tool for captive breeding and stocking programmes, as well as for analyses of population connectivity and genetic structure in this broadly distributed Neotropical migratory fish.

nov., a parasite of Prochilodus lineatus (Valenciennes, 1836) (Characiformes: Prochilodontidae) from the Peixes River, São Paulo State, Brazil

This paper presents the morphological, histological, molecular and ultrastructural data on Myxobolus lomi sp. nov., a parasite of the gill filaments of Prochilodus lineatus from the Peixes River (48º06'38″W; 22º 49'53.1″S), São Paulo State, Brazil. From 20 P. lineatus specimens examined, 90.0% (n=18) were infected. The plasmodia were white and round, measuring 250 to 300μm in diameter and the development occurred in the base of the gill filament. The spores showed symmetrical and smooth valves, with the polar filament having 8 to 11 coils. A thorough comparison with all the Myxobolus species described so far is provided. A partial sequencing of the 18S rDNA gene revealed approximately 1600-bp. The Myxobolus species parasite of P. lineatus did not match any of the Myxozoa available in GenBank. In the phylogenetic analysis, M. lomi sp. nov. is clustered with ten other species and only four of these parasites were from gills. Histological analysis of P. lineatus gills infected by M. lomi sp. nov. revealed numerous well-delimited cysts at the base of the primary lamella, between connective tissue and bone, next to the gill arteries. However no pronounced inflammatory response was found at the infection site.