Genetic variation of the giant mud crab Scylla serrata in relation to metal pollution of Indonesian Mangroves

The giant mud crab Scylla serrata is an important commodity of commercial fisheries in Southeast Asia and the South Pacific. Its high abundance and easy cultivation method make S. serrata trade is one of the busiest markets in Indonesia. The mud crab Scylla spp. is widely distributed in the mangrove ecosystem of Indonesian coasts. Unfortunately, the areas have been suffering from the thriving coastal development, encompassing sectors such as aquaculture, power, minerals, energy and tourism. One major threat is metal pollution as a result of poor pollution management. At molecular level, the exposure of pollutants to S. serrata tissue might lead to the chromosomal aberration and gene mutations. These genetic interferences lead to genetic diversity alteration by changing S. serrata population size and age structure.The objectives of this study are to determine the genetic variation in the giant mud crab S.serata; to determine the metals pollution at Indonesian mangroves, and to see the relationship between genetic variation and metals pollution. Five sampling locations were chosen along Indonesian coasts to represent different anthropogenic pressure. Thirty individuals and 100 grams of sediment samples were collected from each location. Pleopod tissues were preserved in 96% of ethanol for molecular analysis. As for metal pollution analysis, 5 grams of cheliped tissues and the sediment samples were dried in the oven (50°C) for 4 days. Sequence of mitochondrial DNA from the samples was amplified by Polymerase Chain Reaction (PCR) using the mitochondrial DNA cytochrome oxidase subunit I (COI) as a marker. Genetic diversity indices were analysed using software Arlequin vers.3.5. Metals concentration in both sediment and animal tissue was measured using Sector Field Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The pollution level was calculated using indices such as biotasediment bioaccumulation factor (BSAF) and metal pollution index (MPI). Correlation between genetic variation and metals pollution level was computed using Spearman's rank correlation test performed in software Past ver.3.1.8.The results of this study revealed that genetic variation of the giant mud crab S. serrata populations were characterized by high haplotype diversity and low nucleotide diversity. It indicates a bottleneck event due to periods of overexploitation of the giant mud crab populations. Based on MPI values, the sediment of Indonesian mangroves was significantly contaminated by a mixture of hazardous metals such as Cd, Hg, Pb, Cr and a metalloid As. Conversely, the giant mud crab populations were not contaminated by a mixture of those hazardous metals. The correlation test showed that significant correlation between genetic variation and metals pollution was not observed in this study. Despite its insignificant correlation, pollution management along Indonesian coastlines requires further development to avoid the adverse effect of metals pollution in the mangrove ecosystems.