Cytogenetic Effects of Chosen Heavy Metals to Marine Mussel, Modiolus philippinarum L. under Acute Stress  

C.M. Ramakritinan , M. Yokesh Babu , L. Palanikumar# , T. Muneeswaran , A.K. Kumaraguru
Department of Marine and Coastal Studies School of Energy, Environment and Natural Resources Madurai Kamaraj University, Madurai -625021, India
# Present Address: School of Nano-Bioscience and Chemical Engineering Ulsan National Institute of Science and Technology Ulsan Metropolitan City, 689-798, Korea
Author    Correspondence author
International Journal of Marine Science, 2014, Vol. 4, No. 52   doi: 10.5376/ijms.2014.04.0052
Received: 11 Jan., 2014    Accepted: 13 May, 2014    Published: 21 Aug., 2014
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This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:

Ramakritinan et al., 2014, Cytogenetic Effects of Chosen Heavy Metals to Marine Mussel, Modiolus philippinarum L. under Acute Stress, International Journal of Marine Science, Vol.4, No.52 1-9 (doi: 10.5376/ijms.2014.04.0052)

Abstract

The aim of the present study was to investigate the acute toxicity of heavy metals such as Cu, Cd, Pb, Zn and Hg to mussel Modiolus philippinarum of Pudumadam Coast, Gulf of Mannar under continuous flow through bioassay test method. The frequency of nuclear abnormalities such as micronucleus (MN) and binucleus (BN) induced by five heavy metals in bivalve mollusc, M. philippinarum was examined over 96h at intervals of 24h under continuous flow-through toxicity bioassay condition. The estimated LC50 values were 0.019 mg Cu. L-1, 0.158 mg Cd. L-1, 2.025 mg Pb. L-1, 2.823 mg Zn. L-1 and 0.007 mg Hg. L-1 for 96 h exposure. Mercury was found to be highly toxic and zinc was less toxic to M. philippinarum. MN and BN induction showed a significant increase (P < 0.05) with increasing concentration of all five metals. Maximum frequency of nuclear abnormalities was observed for mercury treated mussel after 96h exposure.

Keywords
Continuous flow-through test; Modiolus philippinarum; LC50, cytotoxicity; micronucleus; binucleus

The health of the human life depends on the vitality and vigour of the environment. Deterioration in the environment can cause severe damage to the human health. Also aquatic environment, which covers two-thirds of the planet, is inhabited by the majority of extant species in different ecological niches; moreover many of them are important sources of human food (Frenzilli et al., 2009). Heavy metals are natural components of the biosphere. Living organisms need trace quantity of some heavy metals which include iron, cobalt, copper, manganese, molybdenum, strontium, vanadium and zinc though some are essential for life (Saidi, 2010). However, the excessive amount of metals can be detrimental to living organisms. In the meanwhile, other heavy metals such as cadmium, lead, mercury, chromium etc., in the marine environment i.e., both in seawater and sediments, can accumulate over times into aquatic food chain organisms causing serious illness (Camargo and Alonso, 2006). Sediments and the biota are general metal reservoirs in aquatic environments. The concentrations of heavy metals in water may vary considerably depending on annual and seasonal fluctuations in physico-chemical parameters (Aguilera et al.,2006). The elevated levels of metals in seawater and sediments can cause a severe reduction or, sometimes, elimination of intolerant species, thereby having a significant effect on the diversity and trophic structure of the biological community (Gbaruko and Friday, 2007). The level of accumulation in biota is depend on the chemical effects of metal, its tendency to bind to particular materials and, on the lipid content and composition of the biological tissues as well as the quality of seawater (Gbaruko and Friday, 2007).

Industrial effluents and agricultural run-off into aquatic systems almost certainly burden the ecosystem with mixtures of toxic or potentially toxic metals. They are not only deteriorating the quality of seawater but also disrupt the food web and, bring about morphological, physiological and cytogenetic changes in the aquatic organisms. They also cause mutagenic and carcinogenic effects on living beings (Yadav and Trivedi, 2009). Common mechanisms of genotoxicity includes oxidative stress, impair DNA repair systems, and interruption in signalling pathways, that are related to cell proliferation. However, the intact mechanism of metal carcinogenicity remains largely unknown (Bolognesi et al., 1999).
Genotoxic studies on aquatic organisms exposed to polluted waters containing heavy metals have implicated DNA strand breakages (Kirsch-Volders et al.,2000; Pruski and Dixon, 2002). Micronuclei (MN) can be produced from chromosomal fragments or whole chromosomes that lag at cell division due to lack of centromere, damage in centromere or defect in cytokinesis. These small secondary structures of chromatin are surrounded by membranes located in the cytoplasm and have no detectable link to the cell nucleus (Fenech et al.,2003). The micronucleus assay is one of the most widely used as biomarker for genotoxicity testing in the aquatic organisms thus providing an efficient measure of chromosomal DNA damage occurring as a result of either chromosome breakage or chromosome mis-segregation during mitosis (Bolognesi and Fenech, 2012). Within the last decade, micronucleus tests have played an important role in assessing exposure to water pollutants, and these tests have proved as appropriate tools to provide an early warning of genotoxic threat to the aquatic organisms, their ecosystem and finally to man (Cavas and Ergene-Gozukara, 2005; Lah et al., 2005; Bolognesi et al., 2006; Kim and Hyun, 2006; Palanikumar et al.,2012b). The micronucleus assay is simple, reliable and sensitive for in-vivo evaluation of genotoxic potential of xenobiotics and it does not depend on any karyotypic characteristics of the test animal (Lah et al., 2005).
Marine invertebrates, especially marine bivalves, are used as test species for toxicity testing since these are mostly benthic habitat and filter feeders and some are found in the rocky shores. The marine mussels have been used in assessment of cytogenetic damage (Barsine et al.,2004; Bolognesi et al.,2004; Alink et al., 2007; Sullivan et al., 2007; Bolognesi and Hayashi, 2011). Despite the considerable amount of information available on the effect of heavy metal toxicity to marine bivalves, the impact of heavy metals on micronuclei formation to marine bivalves are quite limited (Sommanee<
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