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Uptake of Zinc by Pteridium aquilinum (Bracken fern) and Response of Clarias gariepinus Juveniles During Chronic and Sub-lethal Exposure
Olaifa, Flora Eyibio & Fabusoro, Abiola A.
Abstract
Summary: Zinc is an essential trace element but can be toxic to fish at elevated concentrations. This study was carried out
to assess the uptake of zinc by Clarias gariepinus juveniles and Pteridium aquilinum during chronic exposure to sub lethal
concentrations. Two experiments (five treatments each: 0.0, 0.8, 1.60, 2.40 and 3.2mg/l zinc chloride) were undertaken
simultaneously in static renewal bioassays for 28 days. One experiment contained 3-4 fronds of P. aquilinum per tank and
the other without it. Each treatment had two replicates (Each having ten C. gariepinus juveniles mean weight 29 ± 2g, length
8 ± 3cm). Haematology, histology, zinc accumulation in tissues of C.gariepinus and P. aquilinum were recorded fortnightly.
Packed Cell Volume, haemoglobin concentration, Red Blood Cells, White blood cells, Lymphocytes, Neutrophils, Mean
Corpuscular Volume, Mean Corpuscular Haemoglobin Concentration and Mean Corpuscular Haemoglobin of C. gariepinus
varied with increasing exposure period. RBC, WBC, LYM, and NEUT differed significantly (p<0.05) among treatments.
Histology (Gills, Kidney and Liver) showed lesions of varying intensities depending on zinc concentration. Bioaccumulation
of zinc in organs of C. gariepinus differed significantly (p< 0.05) with gills at 1.6mg/l Zn having the highest. Zinc in P.
aquilinum differed significantly (p<0.05) with treatments, exposure period and concentration, with the highest concentration
(22.91 ± 2.72 mg/g) at 1.6mg/l of Zn. P. aquilinum absorbed zinc from the water but did not show hyperaccumulator status
in this study.
Keywords
Phytoremediation; Bioaccumulation; Bracken fern; Clarias gariepinus; Haematology; Histology
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