Lead induced malformations in embryos of the African catfish Clarias gariepinus (Burchell, 1822)

Abstract

The effect of lead exposure (100, 300, and 500 microg/L lead nitrate) on embryos of the African catfish Clarias gariepinus were examined by gross morphology and histopathology. Exposition to lead nitrate caused a progressively longer delay in hatching and also reduced the percentage of embryos, which successfully completely hatch from 75% in the control group to 40% in the group exposed to 500 microg/L lead. Categories of gross morphological abnormalities comprised four major ones (irregular head shape, pericardial edema, yolk sac edema, and notochordal defect) and two minor deformations (finfold defect and reduction of pigmentation). The frequencies of recorded morphological malformations increased significantly (P < 0.05) with increasing lead concentration in all stages. Four histopathological categories comprising notochordal defect, gill malformation, eye malformation, and detached skin were recorded. All these malformations were recorded only in the embryos exposed to 300 and 500 microg/L lead. The degrees of histological lesions increased with increasing lead concentration and with length of exposure time. Mean concentrations of lead in the whole embryos were measured and the lowest concentrations of lead were recorded in the control groups (0.3-1.0 microg/g wet wt). Accumulated lead increased significantly (P < 0.05) with increasing dose in all stages. Accumulation of lead in the chorion suggests that the chorion acts as an effective barrier protecting the embryo. Low impact of lead on prehatching stages may be related to both the protective capacity of the chorion and the ability of the perivitelline fluid to concentrate lead. The present results show that (i) lead toxicity was dosage dependent and become evident in gross morphological malformations, followed by histopathological changes, and (ii) early life stages of the African catfish C. gariepinus are a very sensitive bioassay for aquatic lead pollution.

Bioaccumulation of Heavy Metals in Fish (Hydrocynus forskahlii, Hyperopisus bebe occidentalis and Clarias gariepinus) Organs in Downstream Ogun Coastal Water, Nigeria

“…Fish accumulate toxic chemicals such as heavy metals directly from water and diet, and contaminant residues may ultimately reach concentrations hundreds or thousands of times above those measured in the water, sediment and food (Goodwin et al, 2003;Labonne et al, 2001;Osman et al, 2007). Heavy metals are normal constituents of marine environment that occur as a result of pollution, principally due to the discharge of untreated wastes into rivers by many industries.…”

Metal sensitivity of the embryonic development of the ramshorn snail Marisa cornuarietis (Prosobranchia)

“…Some information is available on the effects of lead in fish embryos and larvae (Buhl 1997;Jezierska et al 2000;Osman et al 2007). However, relatively few studies investigated effects on the embryonic development of freshwater snails.…”

“…However, to understand the sublethal effects of metal contaminants on animal health, their action should be studied during the main life cycle phases of an organism, especially during the first stages of development, which are generally considered to be particularly sensitive to toxic and teratogenic metals. Despite availability of large amounts of information on biological effects of metals, by far the highest number of studies has been conducted on model or economically important species (Hamilton 1995;Rougier et al 1996;Clearwater et al 2002;Grosell et al 2006;Osman et al 2007;Vieira et al 2009;Yadav and Trivedi 2009). Further, mortality of adults is the most commonly used parameter in such studies.…”

Effects of Lead Nitrate on catalase production levels in post juvenile Clarias gariepinus (Burchell, 1822)

“…Lead is known to be accumulated in different organs of fish including the bone, gills, kidneys, liver and scales (Javid et al, 2007). Fish accumulate toxic chemicals such as Lead nitrate directly from water and diet, and contaminant residues may ultimately reach concentrations hundreds or thousands of times above those measured in the water, sediments and food (Labonne et al, 2001;Goodwin et al, 2003;Osman et al, 2007).…”