Metal loads and biomarker suite responses in a tropical carnivorous fish indicative of anthropogenic impacts in a Southeastern Brazilian lagoon.

Tropical coastal lagoons are highly productive environments exhibiting high biodiversity. However, the use of these ecosystems by local communities is of concern, since this generally leads to environmental degradation. The Imboassica coastal lagoon, located in Macaé city, in Northern Rio de Janeiro, is an important ecosystem in the state, however, already displaying signs of anthropogenic impacts. Carnivorous fish Hoplias malabaricus specimens were sampled from this impacted site, as well as from a reference area. Fish from Imboassica Lagoon presented lower condition factor, lower cholinesterase activity, and higher percentage of erythrocyte micronuclei when compared to fish from the reference site. Metals in fish from Imboassica Lagoon were always higher than Encantada Lagoon, with some seasonal differences, where some metals were higher in the rainy season compared to the dry season in muscle tissue, with the exception of Cu, Fe, Sr, and Zn; and in the liver, except for Ba, Cd, Cr, Ni, and Sr. Cr and Mn in the edible muscle portion of the fish were higher than the limits established by Brazilian and International legislations as permissible for human consumption, thus leading to concerns regarding public health risks for the local population that use fish as their main protein source.

Evolution of cadmium effects in the testis and sperm of the tropical fish Gymnotus carapo.

The present study investigated the testis and sperm morphology of the tropical fish Gymnotus carapo after exposure to increasing CdCl2 concentrations (5-40 µM) for 24 and 96 h. The treatments induced Cd accumulation in the testis and a decrease in the gonadosomatic index from a 10 µM. Cd induced alterations in testis since 24h; however the extension and severity of damages increased after 96 h in all tested concentrations. Marked variations in the cysts size, proliferation of the interstitial tissue, infiltration of inflammatory cells, necrosis, reduction of germ cells and sperm aggregation was observed in 96 h treated fishes. In this time, there was a complete absence of germ cells in the testis of fish treated with 40 µM. The ultrastructural analysis allowed for the visualization of the initial damages over germ cells, such as the presence of vacuoles in the cytoplasm of spermatogonia, spermatocytes, and spermatids. Exposed fish (20 µM for 24 and 96 h) had alterations in sperm number and morphology. These results are important for establishing a direct correlation between the Cd accumulation and incidence of damages and can help characterize the mechanism of Cd-induced pathogenesis in the male reproductive system.

Mercury-induced dysfunctions in multiple organelles leading to cell death.

Mercury (Hg) is a highly toxic metal that can exert multiple adverse effects, ultimately leading to cell death. Before causing death, the Hg enters the cells and affects diverse intracellular targets. The present study aimed to investigate the structure and function of several organelles or cellular structures, including mitochondria, acidic compartments and vesicles, endoplasmic reticulum elements and microfilaments, following Hg exposure of a human hepatic cell line (HuH-7 cells) to examine the sequence and coordination of the events associated with Hg-induced cell death. Hg exposure led to a progressive decrease in cell viability and induced alterations in cell morphology including cytoplasmic shrinkage and nuclear fragmentation. Hg treatment (10 µM for 12 h) affected multiple intracellular targets simultaneously. These included loss of mitochondrial functionality, pronounced cytoplasmic acidification and dysfunctions in the cytoskeleton and endoplasmic reticulum. This overall Hg-induced toxicity in the human hepatocyte cell line (HuH-7 cells) led to cell death through both apoptosis and autophagy.

Effects of in vitro exposure to mercury on male gonads and sperm structure of the tropical fish tuvira Gymnotus carapo (L.).

This study investigated the progressive effects of HgCl2 in the testis and sperm of the tropical fish tuvira Gymnotus carapo L. exposed to increasing Hg concentrations (5-30 µm) and increasing exposure times (24-96 h). Histopathology and metal concentrations in the testis were observed. Hg concentrations in the testis reached 5.1 and 5.2 µg g(-1) in fish exposed to 20 and 30 µm of Hg, respectively. Hg effects on testicular tissue were observed even at low Hg concentrations, with no alterations in gonadosomatic index. However, the quantitative analysis of the induced alterations (lesion index) demonstrated that the Hg effects in testis became more severe after exposure to higher concentrations (20 and 30 µm) and during longer exposure (72 and 96 h), probably leading to partial or total loss of the organ function. Hg exposure (20 µm) also affected sperm count and altered sperm morphology. This study showed that HgCl2 caused progressive damage to testicular tissue, reduced sperm count and altered sperm morphology. These results are important in establishing a direct correlation between Hg accumulation and severity of lesions.

Effects of dietary methylmercury on liver and kidney histology in the neotropical fish Hoplias malabaricus.

Methylmercury is a potent toxic present in Amazonian fish species due to gold mining activities. In the present work, we investigated the morphological effects of methylmercury in liver and kidney of Hoplias malabaricus feeding contaminated prey fish over 70 days. Two groups of nine mature fish (tested and control) were acclimatized for four weeks to laboratory conditions and then the tested group fed prey fish previously contaminated at an additional level of 0.075 microg MeHg g(-1) at 5-day intervals and over 14 successive intervals whereas control group fed uncontaminated fish. H. malabaricus specimens were then dissected for chemical and morphological analyses. The low and realistic level of MeHg in the prey fish induced a low increase of total mercury in liver (1.8-fold) and muscle (2.2-fold). The biomagnification factor (Hg in predator/Hg in prey) reached 142 in liver and 21 in muscle and was indicative of a relatively fast contamination of internal organs by dietary exposure. The liver of exposed individuals presented leukocyte infiltration, increased number of melano-macrophage centers, necrotic areas and lesions in Disse's space. Evident disorder and chaos in cytoskeleton organization suggest a strong toxic effect in hepatocytes, such as organelles positioning and movement, vesicles traffic and secretion. Head kidney showed large necrosis areas, increased number of melano-macrophages centers, phagocytic areas, intercellular space among parenquimal cells and atypical cells. Injuries and damages to tissues suggest too slow defense mechanisms to immobilize or eliminate ingested methylmercury, demonstrating that the sensitivity of fish cells to methylmercury exposure is higher than it has been previously described in the literature.

Contribution of a medium-sized tropical river to the particulate heavy-metal load for the South Atlantic Ocean.

The Paraíba do Sul River is a medium-sized river, 1145 km in length with a drainage basin of 55,400 km2. The riverine fluxes of particulate metals (Cu, Cr, Zn, Mn and Fe) were investigated over 24 months. Particulate matter samples were monthly collected from April 1994 to March 1996. The first 12-month period presented lower rainfall than the second, although both periods presented average precipitation lower than the regional average. The particulate matter flux in the second period (2,042,080 t) was 250% higher than the first period (821,489 t). The same trend was observed for the associated metals, which presented higher fluxes in the second period. This study highlights the strong dependence of the transported mass on the rainfall, and consequently with the river water discharge. The Paraiba do Sul River presents a low contribution to the world oceans, although the local contribution could be considered relevant.