49 research outputs found

    Total Mercury and Methylmercury Concentration in Fish and Their Reduction through Processing

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    This research has been conducted to study the levels of total mercury and methylmercury, and their correlation in different marine fish species available for consumption in Peninsular Malaysia. Artificial methods have been used to remove mercury from fish. Method for methylmercury determination in fish samples was optimized using response surface methodology (RSM). Total mercury and methylmercury levels were determined using Cold vapor atomic absorption spectrophotometry (CV-AAS) and Gas chromatography-micro electron capture detector (GC-μECD), respectively. Samples of twelve species of common marine fish consumed by Malaysians were collected from local wholesale market in Malaysia. On the basis of total mercury and methylmercury levels measured in commonly consumed fish, two species, long tail tuna and short-bodied mackerel identified with high mercury contents were sampled from east and west coast of Peninsular Malaysia. Methods for elimination of mercury in raw fish fillet has been developed using acidic solutions containing mercury chelating agents. The optimum conditions for methylmercury extraction were found by using acid concentration of 12.118 M, cysteine concentration of 2.375%, solvent volume of 1.5 ml, and extraction time of 35 min. Total mercury and methylmercury levels in fish samples studied were in the range of not detected to 1.010 and not detected to 0.914 μg/g wet wt, respectively. The methylmercury to total mercury ratio ranged from 49.1% to 87.5%, with the highest ratio was in predatory fishes. All of the fish species showed strong positive correlation between methylmercury and total mercury levels (R2>0.86). High levels of total mercury and methylmercury were detected in short-bodied mackerel and long tail tuna. Samples of these two species from east coast of Peninsular Malaysia showed higher levels of mercury compared to those from west coast. In all of the locations, significant positive correlations were found between fish body weight and mercury content. The industrial optimized method produced a solution which can remove mercury from raw fish fillet up to 91%. The optimum conditions for mercury reduction was achieved using cysteine concentration of 1.25 %, EDTA of 275 (mg/L), NaCl of 0.5 (%), pH of 3.75 and exposure time of 18 min. The home-used optimized protocol produced a solution which can remove mercury from raw fish fillet up to 81%. The overall optimal condition resulting to the maximum mercury removal in fish fillet was obtained at combined level of pH of 2.79, 0.5% NaCl, and 13.5 (min) of exposure time

    Reproductive Biology of Horseshoe Crab (Carcinoscorplus Rotundicaude) with Emphasis on Gonad and Gamete Morphology

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    Samples of adult Carcinoscorpius rotundicauda caught from Pulau Lumut, Selangor, from November 2003 to February 2005 were conditioned in the Hatchery Unit, Universiti Putra Malaysia and used for all the experiments. C. rotundicauda was identified based on its morphological characteristics and at the same time age determination was carried out. It is the smallest of four extant species of horseshoe crabs. Male adults were smaller than females. Based on the size estimation, it was found that 75% of collected C. rotundicauda males were of 10 to 11 years old (after 14'~m olt), while 59% of the females were 1 1 to 12 years old (after 1 5th molt). The male reproductive organ was investigated morphologically and histologically. It consisted of testis and spermiducts network which was filled with spermatogenic cells (spermatogonia, primary and secondary spermatocytes) that lied along the basement membrane with spermatozoa close to the testicular lumen. SEM observations showed that a mature spermatozoa consisted of a head with a cap-like acrosomal vesicle, midpiece and a long flagellum. The average size of the sperm head was 4.6 pm while the flagellum was 33 pm in length. The acrosomal filament formed 11 helical coils around the nucleus. Observation on the cross-section of the flagellum showed a 9+0 axoneme pattern without the central tubules. Morphology and histology of mature ovary and egg were studied. The female gonad was located in the prosomal part, consisted of ovarian tubes and oviducts which opened as a pair of gonopores on the ventral side of the opisthosoma. A C. rotundicauda egg (of 2.25 to 2.58 mm in diameter) had a large yolk covered with an elastic chorion with two layers, the outer basement lamina (3.03 pm thickness) and the inner vitelline envelope (43.6 pm thickness). Fecundity of C. rotundicauda ranged from 993 to 7937 eggs per adult, increasing with body size and weight. Interactions between egg and sperm were observed under SEM. Spermatozoa were attached to the outer layer of the egg's chorion. In this study, high sperm concentration (23 - 30 x lo6 spermlml) resulted in numerous sperms attached to the egg surface. Even though many sperms can attach to the egg surface and pass through the egg's envelope, only one will transfer its nucleus into the vitellus and fertilize the egg

    Effects of washing pre-treatment on mercury concentration in fish tissue.

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    The objective of this study was to examine the effect of washing pre-treatment on mercury concentration in fish fillet. Response surface methodology was used to investigate the influence of three variables, pH (1-6.5), NaCl (0-1% w/v) and exposure time (5-30 min) by using a three-factor central composite design. The aim was to obtain the best possible combination of these variables in order to reduce mercury in fish fillet. The experimental data were adequately fitted into a second-order polynomial model with multiple regression coefficients (R(2)) of 0.961. The results indicated that the reduction of mercury in fish flesh significantly depends on the pH of the solution used. The overall optimal condition resulting in the maximum mercury reduction in fish fillet was obtained at a combined level pH of 2.79, NaCl of 0.5% and exposure time of 13.5 min. The optimized protocol produced a solution that can reduce mercury from raw fish fillet up to 81%

    Blood cell histology of horseshoe crab, Tachypleus gigas.

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    Amoebocytes are the main carrier of innate immune system in horseshoe crabs. Cytoplasm of these cells are packed with granules which consist of all coagulation factors and anti-bacterial compounds. Light microscopy (using May-Grunwald and Giemsa staining technique) of 46 blood specimen for both sexes of Tachypleus gigas and observation under Transmission Electron Microscopy (TEM) were performed. Light microscopy revealed that these are ovoid cells containing blue nucleus surrounded by a cytoplasm packed with pink granules. Large and small axes measured 18.8±0.5 and 12.8±0.4 μm, respectively. Total blood cell count (33000 cell mm-3) does not show any significant difference between sexes. TEM of normal and degranulated blood cells revealed that T. gigas hemocytes consist of two type of granules (large and small). Blood cells have all the necessary organelles of normal cells. During the granule formation, fusion of different intermediate granules were observed. Degranulated hemocytes under light microscope and TEM showed cells containing large nucleus and cytoplasmic granules were replaced with a large cytoplasmic vacuole. In light and electron microscopy only one type of hemocyte was observed, the granular cells. These granular cells consist of large and small granules

    Biomagnifications of mercury and methylmercury in tuna and mackerel

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    Seawater may be contaminated by harmful substances, including toxic elements released by human activities. The present study evaluates the total mercury and methylmercury concentrations and their correlations to fish body size in longtail tuna and short-bodied mackerel from Chendring, Kuantan, at east coast and Kuala Perlis at west costs of Peninsular Malaysia during May to November 2007. Total mercury and methylmercury in muscle tissue of 69 samples of longtail tuna and short-bodied mackerel, ranged from 0.180 to 1.460 μg/g and 0.0.169-0.973 μg/g and 0.251-1.470 μg/g and 0.202-1.352, whereas the methylmercury to total mercury ratio ranged from 70% to 83%, respectively. Samples of both species from the east coast showed higher levels of mercury compared to those from west coast. In all of the locations, significant positive correlations were found between fish body weight and mercury content (R(2) > 0.470). The estimated weekly intake of total mercury and methylmercury from the consumption 66.33 g/week of short-bodied mackerel and 18.34 g/week of longtail tuna (based on local dietry survey) was found to be lower than the maximum limit of 5 and 1.5 μg/kg bodyweight established by FAO/WHO and codex, respectively