Abstract
Simple SummaryThis investigation was executed to establish the threshold level of inorganic and organic mercury incorporated in the diet of juvenile olive flounder in relation to the broken-line regression model for the percentage of weight gain of fish. Organic mercury incorporated diet resulted in more toxic behavior than its counterpart inorganic mercury in olive flounder. Mercury was found to be more biomagnified in kidney tissue than liver and gill tissues of fish. The study has importance in terms of knowledge on mercury toxicity in marine fish.Mercury as one of the most toxic elements can be present in organic or inorganic form in marine fishes, which may cause a potential threat to public health. In this study, we investigated to determine the dietary organic (O-Hg) and inorganic (I-Hg) mercury threshold levels on induced mercury toxicity in juvenile olive flounder, Paralichthys olivaceus as a marine fish model. Twenty-eight fish averaging 3.1 ± 0.05 g (mean ± SD) were arbitrarily assigned to each of 27 tanks. Each tank was arbitrarily restricted to triplicates of nine experimental diets for eight weeks. The experimental diets were manufactured to contain 0 (Control), 10 (I-Hg10, O-Hg10), 20 (I-Hg20, O-Hg20), 40 (I-Hg40, O-Hg40) and 160 (I-Hg160, O-Hg160) mg/kg diet in organic form as methylmercury (MeHg) or in inorganic form as mercuric chloride (HgCl2). At the termination of the experimental trial, weight gains (WGs) of fish fed the control and 10 (I-Hg10, O-Hg10) diets were remarkably higher than those of fish fed the 20 (I-Hg20, O-Hg20), 40 (I-Hg40, O-Hg40) and 160 (I-Hg160, O-Hg160) (p < 0.05). Specific growth rate and feed efficiency of fish fed control and 10 (I-Hg10, O-Hg10) diets were significantly higher than those of fish fed 40 (I-Hg40, O-Hg40) and 160 (I-Hg160, O-Hg160) diets. In comparison to the dietary inorganic mercury, dietary MeHg bioaccumulation rates were significantly higher in the tissue levels according to the dietary inclusion levels. MeHg accumulated mostly in kidney, followed by liver and gill tissues. HgCl2 accumulated in tissues, in decreasing order, liver > kidney > gills. A broken-line regression model for percentage of WG indicated that the threshold toxicity level for an Hg-incorporated diet of juvenile olive flounder could be 13.5 mg Hg/kg in the form of HgCl2 and 8.7 mg Hg/kg in the form of MeHg.
Highlights
Mercury (Hg) is a naturally occurring element found in air, water, and soil [1,2]
Studies on the effects of mercury on the health of fish have been undertaken, these studies focused on waterborne exposure to inorganic mercury or dietary exposure to methylmercury, and most studies dealt with field-oriented research [20,34,35,36,37,38,39]. As both organic and inorganic mercury are toxic in nature, this study aims to compare the dietary threshold levels for the organic and inorganic mercury toxicity in juvenile olive flounder by using methylmercury (MeHg) and mercuric chloride (HgCl2 ) as dietary organic and inorganic sources of mercury, respectively
Growth Performances week experiment was conducted in the facilities of the Feeds and Foods Nutrition Research Center, Pukyong
Summary
Mercury (Hg) is a naturally occurring element found in air, water, and soil [1,2]. It may exist in three chemical forms: (1) natural mercury, which may be found in liquid and gaseous states;(2) inorganic mercury compounds, including mercurous chloride (Hg2 Cl2 ), mercuric chloride (HgCl2 )and mercuric sulfide (HgS); and (3) organic mercury compound, especially methylmercury (MeHg) [3].All forms of mercury are toxic [4], and organic MeHg is neurotoxic compared to inorganic HgCl2 in fish [5]. Mercury (Hg) is a naturally occurring element found in air, water, and soil [1,2]. It may exist in three chemical forms: (1) natural mercury, which may be found in liquid and gaseous states;. All forms of mercury are toxic [4], and organic MeHg is neurotoxic compared to inorganic HgCl2 in fish [5]. Mercury is a naturally occurring element, human or anthropogenic activities, through industrial processes, have led to widespread distribution of toxic mercurial derivatives throughout the biosphere [6]. The natural mercury is biologically transformed into organic mercury by different types of microorganisms, basically anaerobic bacteria [7].
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