Nilonema gymnarchi (Nematoda: Philometridae) and trace metals in Gymnarchus niloticus of Epe lagoon in Lagos State, Nigeria.

The presence of trace metals in the sediment, water, and biota of the Epe lagoon has been recently linked to oil exploration and municipal perturbations around the lagoon. The study was aimed at assessing the concentrations and associated health risks of Fe, Zn, Cu, Ni, Pb, Cd, Cr, Mn, Co and V in the water, sediment, and Gymnarchus niloticus of Epe lagoon and to evaluate the role of the enteric parasite Nilonema gymnarchi in bioaccumulation of the metals in the fish. The temperature, pH, redox potential, conductivity, turbidity, dissolved oxygen (DO), total dissolved solids (TDS), and salinity were determined in-situ using a handheld multi-parameter probe (Horiba Water Checker Model U-10). The concentrations of Fe, Zn, Cu, Ni, Pb, Cd, Cr, Mn, Co, and V were determined in the surface water, bottom sediment, Gymnarchus niloticus, and its enteric parasites, Nilonema gymnarchi in Epe lagoon using the Flame Atomic Absorption Spectrometer (Philips model PU 9100). The bioaccumulation factors and target hazard quotients of the trace metals in the infected and uninfected fish were estimated and compared. The intestinal tissue sections of the infected and uninfected fish were examined using a binocular dissecting microscope (American Optical Corporation, Model 570) using hematoxylin and eosin (H&E) stain. Biochemical markers such as reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (MDA) were determined in the liver of the infected and uninfected fish. The SOD level was higher in the uninfected fish than the infected ones supports the indications deduced from the bioaccumulation analysis. Strong positive correlations between SOD and most of the metals- Fe (0.916), Zn (0.919), Cu (0.896), and Ni (0.917) suggests that the metals may have inflicted more toxicity in the uninfected. The histopathological comparisons made between the uninfected and infected fish showed consistency with the outcomes of other comparisons made in this study. These evidence were marked by tissue alterations in the infected fish ranging from no observed changes to mild alterations, while the uninfected exhibited more severe tissue injuries such as hemorrhagic lesions, severe vascular congestion, edema, the increased connective tissue of the submucosa, and vascular congestion. The condition factors of the infected (0.252) and uninfected (0.268) fish indicated slenderness and unfitness possibly due to environmental stressors such as trace metals. The parasitized fish showing better-coping potentials than the uninfected, coupled with the significant bioaccumulation interferences exhibited by the parasite Nilonema gymnarchi is an indication that the parasites may be a good metal sequestration agent for the fish and can be used to forestall the significant health hazard quotient posed by the current level of iron and the synergy of all metals analyzed in the lagoon.

Role of Intestinal Helminth Parasite of Macrobrachium vollenhovenii-Cucullanus sp. in Host Metal Accumulation in Epe Axis of the Lekki Lagoon, Lagos, Nigeria.

This paper assesses the role of intestinal helminth parasite of Macrobrachium vollenhovenii on host metal accumulation in Lekki lagoon, Lagos, Nigeria. Lead, zinc, copper, chromium and iron concentrations were determined in water, sediment, intestinal parasite, intestine of infected and non-infected prawns. Intestinal nematode parasite Cucullanus sp. was identified. Pb and Cr were not detected in the water and sediment. The sediment had higher concentrations of the metals than the water medium, and exceeded the WHO limits for Zn, Cu and Fe. Cucullanus sp. accumulated Zn 19 times, Cr several thousand times more and Fe 11 times more than the host intestine (wet wt). This parasite could have accumulated these metals from its host, reducing the concentration of these metals in the tissues of the infected prawns compared to non-infected ones. The infected and non-infected prawns accumulated Zn and Fe several times more than the water medium. The parasite influenced metal accumulation in the host tissue and pose ecological risk.

Response of some antioxidant parameters in post juveniles of Clarias gariepinus after exposure to Nigerian crude oil (Forcados, Bonny Light and Qua-Iboe).

The adverse effect of crude oil on aquatic ecosystem is a modern day peril. This study investigated the acute toxicities of some Nigerian crude oil (Forcados, Bonnylight and Qua-Iboe) against Clarias gariepinus and the antioxidant enzyme response of the fish to the pollutants. The toxicity assessment was based on LC50 at 96 h. Static renewal bioassays were used to determine the toxicological effects of the 3 crude oils on the antioxidant enzymes of post juveniles Clarias gariepinus using the liver. The 96 h LC50 value for Qua Iboe was 18.966 mL L(-1), Forcados, 2.776 mL L(-1) and Bonny light, 3.948 mL L(-1), indicating that Forcados is the most toxic of the crude oils. Induction of the Glutathione-S-transferase (GST), Glutathione (GSH), Superoxide dismutase (SOD) and Catalase (CAT) in the liver of Clarias gariepinus exposed to Forcados and Bonny light for a period of 28 days was inhibited while it was enhanced in Qua-Iboe crude oil. Malondialdehyde (MDA) levels increased with increasing toxicity and exposure time. SOD, CAT, GSH, GST and MDA are reliable environmental biomarkers for crude oil induced oxidative stress in Clarias gariepinus and therefore useful biological indicators of environmental contamination in the aquatic ecosystem.