Background

Crabs belong to a group of animals knows as decapods crustaceans. Most of the marine crabs occurring along the Persian Gulf coasts belong to the family Portunidae. The blue swimming crab, P. pelagicus is widely distributed throughout the coastal and estuarine areas of the tropical western Pacific and Indian oceans (Kumar et al., 2000). P. pelagicus is one of the important representatives of decapod crustacean and a species commonly found in Persian Gulf coasts. Crabs the capability of accumulating heavy metals (Reinecke et al., 2003). Crabs are an excellent bioindicator of metal contamination and can be used to effectively and accurately monitor metal level for several reasons.

Considerable studies have also been carried out on the biochemical composition and heavy metals accumulation in crab P. pelagicus of the Egyptian and Iranian coasts (Ghazaly, 1988; Zaghloul, 2003; Sallam et al., 2006; Hosseini et al., 2012; Khoei and Abdi Bastami, 2013).

Environmental pollution has increased substantially in the last decades due to a great number of industrial, agricultural, commercial and domestic waste, effluents and emissions as well as hazardous substances. Some heavy metals such as Hg, Cr, Cd, Ni, Cu, Pb etc. introduced into environmental water system may pose high toxicities on the aquatic organisms (Wu and Zhao, 2006; Ambreen et al., 2015). In order to evaluate the environmental impact of these pollutants on the marine ecosystem it has become important for a rapid assessment of their toxic effects on the marine organisms.

The aim of this work is therefore to determine biochemical composition (protein, fats carbohydrates) and the concentration of five metals, namely cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), and iron (Fe) in muscle tissue of male and female crab P. pelagicus and their possible health effect on man.

1 Materials and Methods

Fresh samples of P. pelagic were collected from the catches of the trawling net at the landing site of Al-faw city (Al-najaa region on bank of the shatt Al-Arab river) (Figure 1), during summer and winter seasons in 2017. Specimens were measured for carapace width (CWmm) by means of vernier calipers. A total of 20 crabs, 10 male and 10 female were chosen for analysis (three replicates of each sex from each size range).

The meat from the abdomen was extracted, a heavy pestle was used to crack the chelipeds and the meat was removed by means of a spatula.

Muscle tissue of crab was subjected to analysis the biochemical composition such as, crude protein, carbohydrate and lipid (fat) of the males and female on basis of the dry weight. All analysis was carried out in triplicates.

Three biochemical compositions such as protein, fat and, carbohydrate content were measured using the method of Association of Official Analytical Chemists (AOAC, 2000). Nitrogen was estimated by the micro-Kjeldahl method and the percentage nitrogen was converted to crude protein by multiplying by 6.25. Carbohydrate was determined by difference. All determinations were performed in triplicates. Concentrations of iron (Fe), zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in muscle tissue samples of each crab specimen were determined using the atomic absorption spectroscopy technique in marine biology department, marine science center, Basrah university.

The statistical interpretation of the tabulated data was performed by using SPSS (21.0 version) for the mean standard deviation at 5% level of significance.

2 Results and Discussion

Table 1 shows mean carapace width (CW) of female and male species of crab P. pelagic in both summer and winter seasons. The mean carapace width (CW) for male crab were found to be higher than mean carapace width (CW) for female crab during both seasons. Similar results were reported for the crab P. pelagic in other researches (Kangas, 2000; Abdul-Saheb, 2012). These results are consistent with the above-reported for same species.

The mean percentages of the three biochemical compositions in the muscle tissue of P. pelagic are presented in Table 2. Protein was apparently high level of protein, was reported (81.47%) in the males of current study. High level of fat (lipid) content was reported (8.80%) in the females. Likewise higher level of carbohydrate content was noticed (6.72%) in females.

Figure 2 and Figure 3 showed the mean percentages of the three biochemical contents in relation to the crab’s body size (CWmm). The largest males, with carapace width between 90-135mm, had the highest protein percentage (79.45%), the highest lipids (9.36%) and carbohydrates (7.3%) respectively (Figure 2) while largest femles, with carapace between 80-120mm, had the highest protein percentage.

Furthermore, values recorded in this study were higher than those reported for other edible crab species including Podophthalmus vigil (Radhakrishnan and Natarajan, 1979), Chaceon Affinis (Vasconcelos and Braz, 2001), while for the same species P. pelagicus in particular (Sallam et al., 2006). Akbar et al. (1988) reported a range of 54-75% for protein and 3.2-6.2% for lipids for P. pelagicus in Pakistan, while Pillay and Nair (1978) reported 40.1-60.7% for protein and 1.3-6.15% for lipids for the same species in India.

Mean concentrations (μg/g) of the heavy metals Cd, Pb, Zn, Cu, and Fe in the muscle tissues of both sexes (Table 3) indicated that iron was the highest accumulated metal (68.62, 45.24 μg/g) followed by copper (45.24, 23.16 μg/g), zinc 18.98, 9.67 μg/g), lead (1.74, 0.87 μg/g) while cadmium was lowest (0.43, 0.74 μg/g) in tissues of male and female respectively.

The average Cu, Zn, and Fe muscle tissues concentrations in males were slightly higher than the average levels for females. Significant differences were observed only for Fe and Cu (p<0.05) when compared with each other. The order of average heavy metal concentrations found in muscle tissues samples in both male and female species was: Fe>Cu>Zn>Pb>Cd.

It was reported that the relationship between metal accumulation and sex may be due to the difference in metabolic activities between the males and the females, and the faster-growing sex (usually the female) can be expected to contain lower concentrations of metals (Pourang et al., 2004; Yilmaz and Yilmaz, 2007; Sallam and Gab-Alla, 2009; Umunnakwe and Ogamba, 2013). Thus, the mean concentrations of these metals in males were found to be slightly higher than the females.

Cd concentrations in P. pelagic were the lowest heavy metal concentrations followed by Pb, while Fe, Cu, Zn concentrations were highest level observed in both two sexes.

Results showed that Fe had the higher concentrations in the tissues of crab and Pb element had concentrations least. This observation may be due to the major functional differences in their body. The research same, the comparison on heavy metal accumulation between all tissues crustaceans show that bioaccumulation of heavy metals was more in gills than other tissues (Pourang et al., 2005; El Gendy et al., 2015).

Authors’ contributions

All authors in this paper have contributed equally toward the publication of this paper.

Acknowledgments

We would like to thank the members of the Marine Biology Department, Marine Sciences Center, Basrah University, for help me in accomplishing this work and for their valuable advice and suggestions.

References

Abdul-Sahib I.M., 2012, Some biological aspects of the swimming crab Portunus pelagicus (Linnaeus, 1766) (Decapoda: Portunidae) in NW Arabian Gulf Mesopot. J. Mar. Sci., 2012, 27(2): 78-87

Akbar Z., Qasim R., and Siddiqui J.A., 1988, Seasonal variations in biochemical composition of edible crab (Portunus pelagicus Linneaus) J. Isl. Acad. Sci., 1(2): 127-133

Ambreen F., Javed M., and Batool U., 2015, Tissue Specific Heavy Metals Uptake in Economically Important Fish, Cyprinus carpio at Acute Exposure of Metals Mixtures. Pakistan J. Zool., 47: 399-407

AOAC, 2000, Official Methods of Analysis. 17th ed. Gaithersburg, Maryland, USA, AOAC International

El Gendy, A. Al Farraj, S. and El Hedeny, M. 2015, Heavy Metal Concentrations in Tissues of the Shrimp Penaeus semisulcatus (De Haan, 1844) From Jazan, Southern Red Sea Coast of Saudi Arabia, Pakistan J. Zool., vol. 47(3): pp. 671-677

Ghazaly K.S., 1988, The bioaccumulation of potential heavy metals in the tissues of the Egyptian Edible marine animals, Part 1. Crustaceans. Bull. Biol. Ins. Ocean. Fish A.R.E., 4(2): 71-77

Hosseini M., Abdi Bastami A., and Khoei J.K., 2012, Concentrations of Heavy Metals in Selected Tissues of Blue Swimming Crab, Portunus pelagicus (Linnaeus, 1758) and Sediments from Persian Gulf, World Applied Sciences Journal 19(10): 1398-1405

Kangas M.I., 2000, Synopsis of the biology and exploitation of the blue swimmer crab, Portunus pelagicus Linnaeus, in Western Australia. Fish. Res. Rep. Fish. West Aust. 1, 121: 1-22

Khoei J.K., and Abdi Bastami A., 2013, Mercury Concentrations in Tissues of Blue Swimming Crab Portunus pelagicus and Sediments from Khark Island, World Applied Sciences Journal 21(9): 1391-1397

Kumar M., G. Ferguson, Y. Xiao, G. Hooper, and S. Venema, 2000, Studies on reproductive biology and distribution of blue swimmer crab (Portunus pelagicus) in South Australian Waters. Research Report Series, 47: 1324-2083

Methods of Mineral Analysis, Atomic Absorption Spectrophotometer. International Institiute of Tropical Agriculture. (IITA), 2002

Pillay K.K., and Nair N.B., 1973, Observations on the biochemical changes in gonads and other organs of Uca annulipes, Portunus pelagicus and Metapenaeus affinis (Decapoda: Crustacea) during the reproductive cycle. Mar. Biol., 18: 167-198

https://doi.org/10.1007/BF00367985

Pourang N., Dennis J.H., and Ghourchian H., 2004, Tissue distribution and redistribution of trace elements in shrimp species with the emphasis on the roles of metallothionein. Ecotoxicology 13: 519

https://doi.org/10.1023/B:ECTX.0000037189.80775.9c

Pourang N., Dennis J.H., and Ghourchian H., 2005, Distribution of heavy metals in Penaeus semisulcatus from Persian Gulf and possible role of metallothionein in their distribution during storage. Environ. Monit. Assess., 100: 71-88

https://doi.org/10.1007/s10661-005-7061-8

Radhakrishnan C.K., and Natarajan R., 1979, Nutritive value of the crab Podophthalmus vigil (Fabricius). Fish Tech., 16: 37-38

Reinecke A.J., R.G. Snyman, and J.A.J. Nel, 2003, Uptake and distribution of lead (Pb) and cadmium (Cd) in the freshwater crab, Potamonautes perlatus (Crustacea) in the Eerste River, South Africa. Water Air Soil Pollution, 145: 395-408

Sallam W.S., Temraz T.A., and Gabr H.R., 2006, Biochemical compositions and heavy metals accumulation in some commercial crustaceans from the Mediterranean coast off Port Said, Egypt. J. Egypt. G. Soc. Zool, (Inv. Zool. and Parasitol.), 51D: 127-141

Sallam W.S., and Gab-Alla A. A-F.A., 2009, Edibility assessment of the swimming crab Charybdis natator (Brachyura: Portunidae) from the Gulf of Suez, Red Sea, Egypt, Egypt J. Aquat. Biol. and Fish., Vol. 13, No 1:43-54

Umunnakwe J.E., and Ogamba A.S., 2013, Bioaccumulation of Heavy Metals In Crabs At Bundu-Ama Community, Port Harcourt. Journal of Environment and Earth Science, www.iiste.org. 3(14): 11-21

Vasconcelos P., and Braz N.R., 2001, Proximate Composition of The Deep Sea Crab, Chaceon Affinis From An Exploratory Fishery of Maderia Island (Portugal-Eastern Central Atlantic) North West Atlantic Fisheries Organisation. 1-6

Wu S.D., and Zhao H.F., 2006, The analytical methods in the monitoring of water and wastewater, China Environmental Science Press, Beijing, 2006

Yilmaz A.B., and Yilmaz L., 2007, Influences of sex and seasons on levels of heavy metals in tissues of green tiger shrimp (Penaeus semisulcatus de Hann, 1844). Food Chem. 101

https://doi.org/10.1016/j.foodchem.2006.04.025

Zaghloul S.S., 2003, Studies on the reproductive biology and rearing of portunid crabs in Suez Bay. Ph.D. thesis, Suez, Suez Canal University