Allozyme polymorphisms and heavy metal levels in the green-lipped mussel Perna viridis (Linnaeus) collected from contaminated and uncontaminated sites in Malaysia C.K. Yap * , S.G. Tan, A. Ismail, H. Omar Department of Biology, Faculty of Science and Environmental Studies, Universiti Putra Malaysia (UPM), Serdang, Selangor 43400, Malaysia Received 18 March 2003; accepted 12 May 2003 Abstract It has been widely reported that heavy metal contamination in coastal waters can modify the allozyme profiles of marine organisms. Previous studies have recorded elevated metal concentrations in sediments and mussel tissues off Peninsular Malaysia. In the present study, horizontal starch gel electrophoresis was carried out to estimate the levels of allelic variation of the green-lipped mussel, Perna viridis, collected from one contaminated and three relatively uncontaminated sites off Peninsular Malaysia. Fourteen polymorphic loci were observed. In addition, the concentrations of cadmium, copper, lead, mercury and zinc were determined in the sediments and in the soft tissues of the mussels. Mussels from contaminated site, evidenced by high metal pollution indices (MPI) of the sediment and the mussel tissues, showed the highest percentage of polymorphic loci (78.6%), while those collected from the uncontaminated sites had lower MPI of the sediment and mussel tissue, and exhibited lower percentages of polymorphic loci (35.7 – 57.1%). The population from the contaminated site showed the highest excess of heterozygosity (0.289) when compared to that of the populations from the three uncontaminated sites (0.108 – 0.149). Allozyme frequencies at the phosphoglucomutase (PGM; E.C. 2.7.5.1) locus also differed between the contaminated and uncontaminated populations. Previous studies have shown that exposure to heavy metals can select or counter-select for particular alleles at this locus. The present results suggest that allozyme polymorphism in P. viridis is a potential biomonitoring tool for heavy metal contamination but further validation is required. D 2003 Elsevier Science Ltd. All rights reserved. Keywords: Perna viridis; Allozymes; Heavy metals; Malaysia 1. Introduction Evidence is increasing to suggest that genetic polymor- phism of organisms (animals and plants) is linked to adaptation to specific environmental parameters (Nevo et al., 1986; Nevo, 1990; Koehn and Bayne, 1989; Hummel and Patarnello, 1994; Gillespie and Guttman, 1999). This is due to the fact that the use of genetic biomarkers of environmental pollution has become a topic of interest in the literature recently. In particular, the impact of pollutants on the genetic structure of marine organisms has been demonstrated by several studies (Nevo et al., 1986; Ben- Shlomo and Nevo, 1988; Nevo, 1990; Ma et al., 2000; Moraga et al., 2002; Mulvey et al., 2002; Ross et al., 2002; Sokolowski et al., 2002). For example, it was found that using artificial heavy metal pollution as an environmental stress, potential differences between genetic variants of the marine gastropods, Cerithium scabridum, could be identi- fied (Latvie and Nevo, 1986a). For each population and for each pollutant, specific resistant alleles would become pronounced if organisms were continually exposed to a specific pollutant. Studies have demonstrated that the higher the level of genetic variation in a population the greater the chance that the population will be able to tolerate exposure to heavy metals (Klerks and Weis, 1987). Horizontal starch gel electrophoresis had been widely used to investigate the relationship between heavy metal exposure and protein allozyme variation in marine gastro- pods (Latvie and Nevo, 1982, a,b) and blue mussel Mytilus edulis (Koehn, 1991; Gosling, 1992; Beaumont and Toro, 1996). Recently, by using protein allozyme study, Yap et al. 0160-4120/$ - see front matter D 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0160-4120(03)00144-2 * Corresponding author. Tel.: +60-3-89486101x3603; fax: +60-3-89432508. E-mail address: yapckong@hotmail.com (C.K. Yap). www.elsevier.com/locate/envint Environment International 30 (2004) 39 – 46