Redox-active metals and oxidative stress-mediated myopathies in Callinectes amnicola, blue crab populations from impacted sites of the Lagos Lagoon: inferences for adverse ecological outcomes.

While oxidative stress pathways are associated with a wide variety of tissue pathologies, its applications for evaluating and discerning ecological risks are limited. This study seeks to associate trends of lipid peroxidation and oxidative stress to risks of muscle pathologies in blue crabs inhabiting regions of the Lagos Lagoon. Crab samples (n = 520) were selected from pollution-impacted sites of the lagoon at Iddo, Ajah, Okobaba, Makoko, and the mid-lagoon area (control site). Antioxidant enzyme capacity, i.e., superoxide dismutase, catalase, glutathione peroxidase (GPx), and glutathione-S-transferase, and lipid peroxidation were evaluated in the muscle tissue of the blue crabs. The study findings showed distinct patterns of metal uptake in muscle, with redox-active metals (Cu and Zn) and redox-inactive metals (Pb and Cd) exhibiting site-specific differences. Additionally, there were changes in antioxidant modulation, lipid peroxidation, and the presence of associated myopathies. Blue crabs from sites (Makoko and Ajah) with greater uptake of redox-active metals (Cu and Zn) in muscle tissue showed higher trends of lipid peroxidation and the most prevalence of severe regression-type myopathies. Sites with lower uptake of redox-active metals showed the predominance of circulatory-type myopathies. This study also provides evidence of severe necrosis and myositis associated with digenean parasite cysts in crab muscle. Pathological evidence of severe skeletal muscle deterioration in the presence of greater lipid peroxidation could have implications for motor-neuron activity and reduced force-generating capacity necessary for adaptive responses in the wild. We conclude that elevated uptake of redox metals could aggravate the onset of myopathies in wild populations.

Metal uptake, oxidative stress and histopathological alterations in gills and hepatopancreas of Callinectes amnicola exposed to industrial effluent.

Metal uptake by biota due to elevated environmental concentrations elicits oxidative stress and could lead to pathological outcomes. The relationship between the histopathological profile of hepatopancreas and gills and altered biochemical features (antioxidant enzymes i.e. GSH, GPx, CAT, SOD, lipid peroxidation (MDA) and serum protein) in the blue crab, Callinectes amnicola from contaminated parts of the Lagos Lagoon was investigated. Monthly crab, sediment and surface water samples were taken from effluent receiving areas of the Lagos lagoon i.e. Makoko, Okobaba, Iddo, Ikoyi and Mid-lagoon (control site) over an 18-month period and analyzed for metal levels (Pb, Cd, Zn and Cu). Significantly higher levels of GPx and lower levels of Pb, Zn and Cu was recorded in gills and hepatopancreas of crabs from the mid-lagoon compared to crabs from other sites. Reaction patterns of gills across the different sites of the lagoon included regressive (ranging from epithelial lifting, disruption of pilaster cells, detached cuticle to focal necrosis) and circulatory disruptions (oedema); increased activity of GSH and GPx in gills were positively correlated with lesions of lower importance factor. Reaction patterns in hepatopancreas were more regressive including vacuolation/infiltration of fatty lobules, necrosis, granuloma, disintegrated lumen, atrophied tubules and loss of lobular hepatocyte structure; increased activity of GSH, GPx and CAT were positively correlated with lesions of low importance factor in the hepatopancreas. Findings show that lesions in both gills and hepatopancreas of the blue crab could be associated with uptake of metals, depleted antioxidant activity and incidence of lipid peroxidation in tissue.