Impacts of trace metals on African common toad, Amietophrynus regularis (Reuss, 1833) and depuration effects of the toad's enteric parasite, Amplicaecum africanum (Taylor, 1924) sampled within Lagos metropolis, Nigeria
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CellPress
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The study aimed at assessing the depuration potentials of endoparasite, Amplicaecum africanum on trace metals in
its toad host, Amietophrynus regularis at sites of significant anthropogenic perturbations within the Lagos
metropolis, in Nigeria. A total of 120 toads of both sexes, alongside 45 soil samples were collected from each of
three (3) stations labeled Dumpsite, Lagoon front and Highrise, using hand nets and by hand-picking between
February and October, 2018. The intestinal tissues sections of the toads were examined using a binocular dissecting
microscope (American Optical Corporation, Model 570) and hematoxylin and eosin (H&E) stain.
Oxidative stress in toad intestine was assessed by estimating the levels of glutathione peroxidase (GPx), superoxide
dismutase (SOD), catalase (CAT), and lipid peroxidation (MDA). Trace metals in the water, soil, toad liver,
intestine and parasite, Amplicaecum africanum were tested using Atomic Absorption Spectrophotometry (Philips
model PU 9100). Lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd), and chromium (Cr) were detected in the
toads, with the infected toads having lower concentrations of most trace metals than the uninfected toads,
irrespective of the locations and sex. Strong negative correlations between parasitological indices and concentrations
of trace metals in the toads suggest that the parasites might have taken up significant amounts of trace
metals from the host. The study demonstrated the potentials of parasite, A. africanum to depurate trace metal
burden in Amietophrynus regularis. When the dominant factor impacting the toad is the parasitic infection, parasite
intensity determines the trade-off between parasitological harm and depuration benefit to the host. Hence, under
controlled conditions, parasites may serve as bioremediation agent in the event of pollution. Depuration potential
of A. africanum in the study was supported by the mild tissue alterations observed in the intestine of infected
toads, compared to the uninfected counterparts, which exhibited severe glandular hyperplasia, increased connective
tissue, and severely stunted villi. Consistently lower activities of biochemical biomarkers which characterize
the uninfected toads compared to the infected, irrespective of the sex and stations, further corroborate
drawn inferences.
Keywords
QH Natural history, QH301 Biology