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Histology changes in the marine tilapia by mercury and cysteine in a multi-tissue approaching

1 Zulkipli Siti Zuraida, Mok Wen Jye*
2

1 Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu, 21030 Kuala Nerus,
Terengganu, Malaysia.
2 Institute of Marine Biotechnology, Universiti Malaysia Terengganu, 21030 Kuala Nerus,
Terengganu, Malaysia.

* Corresponding author: mok.jye@umt.edu.my

Abstract:

Mercury is a dangerous environmental pollutant that can be released via natural and anthropogenic
processes into the aquatic environment. Thus, several studies on the reduction of mercury concentration
in fish were conducted and one of the preferable methods is by using cysteine in feed to reduce the
mercury concentration. The implementation of the cysteine and mercury in the fish feed as premix diet
was used to identify the effectiveness of cysteine to reduce the mercury level in fish for a month. The
fish were reared in random five experimental tanks with different dietary consisting of T1 (control as
basal fish pellet); T2 (basal fish pellet + cysteine only); T3 (1-week of basal fish pellet + mercury
followed by 3-week basal fish pellet + cysteine); T4 (basal fish pellet + mercury only); and T5 (basal
fish pellet + mercury +cysteine). In this study, analysis of mercury concentration and histopathology
were carried out. The highest mercury concentrations (µg/g) were found in the brain > kidney > liver >
intestine > muscle > gill and the level of mercury was particularly high in the treatment involved in
mercury diets. T3 that was exposed to one week of mercury and then treated with three weeks of
cysteine showed a positive recovery of the proportion available for gas exchange in gill (PAGE%: 63.50
%), total area of lipid accumulation in liver (3.12%), Bowman space’s size of the kidney (218.25 µm)
and number of goblet cell found in intestine (29), similar with T1 (control). Contradictory, treatment
with 4-week mercury (T4) showed negative findings with severe damage of gill structure (unavailable
PAGE% calculation), high lipid accumulation in liver (19.61%), large Bowman space’s size (457.02
µm) and increasing in number of goblet cell (114). In conclusion, cysteine was an effective chelating
agent to reduce mercury contamination in fish.

Keywords: Mercury, Cysteine, Diets, Organs, Histology