Acetes shrimp were sampled from land-based catches using push nets and sea trawling more than 5 nautical miles (nm) offshore along the west coast of Peninsular Malaysia, August 2007 to September 2008. A global positioning system (GPS) was used to indicate the geographic location of each sampling location (Table 1, Fig. 1) Samples were preserved in 70% ethanol immediately after collection. Species and sex of Acetes shrimp were identified using the key characters described in Omori (1975), under a Leica dissecting microscope (Leica ZOOM 2000™, model no. Z45V, Germany).[Table 1], [Fig.1]2.2 DNA Extraction, Amplification, SequencingDNA was extracted from 25 g of muscle sample, using the i-genomic CTB mini DNA extraction kit (iNtRON Biotechnology, Inc., South Korea). using PCR (Saiki et al., 1988) with the primer pair LCO1490 (5'–GGT CAA CAA ATC ATA AAG ATA TTG G–3') and HCO2198 (5'–TAA ACT TCA GGG TGA CCA AAA AAT CA – 3') (Folmer et al., 1994). Each PCR reaction mixture contained 2.5 µL of 10× PCR buffer (Vivantis), 1.5 mM MgCl2 (Vivantis), 50 µM of each dNTP (Vivantis), 1 unit (U) of Taq polymerase (Vivantis), 0.3 µM of each primer (1st BASE Pte Ltd, Singapore), 2 µL of DNA template (50 ng) and brought to a final volume of 25 µL with deionized water. PCR of the COI gene was performed on an Eppendorf Mastercycler® Gradient (Eppendorf, Hamburg, Germany) with the following profile: initial denaturation at 94 oC for 60 s; five cycles at 94 oC for 30 s, 45 oC for 90 s and 72 oC for 60 s; 35 cycles at 94 oC for 30 s, 51 oC for 90 s and 72 oC for 60 s; followed by a trailing edge......middle of the paper......splitting frequencies were less than 0.01, 25% of samples were discarded as burn-in (sump burnin = 1000) . The remaining trees were used to calculate the posterior probabilities (PP) and to produce the 50% majority rule consensus tree after discarding the burn-in samples in each analysis. Probabilities of 95% or greater were considered significant support. All phylogenetic trees were rooted with Sergestes similis (GenBank accession number: DQ882152) as the outgroup and visualized with TreeView 1.6.6 (Page, 1996). Furthermore, the haplotype network (for A. indicus and A. sibogae) was constructed using the TCS 1.13 software method (Clement et al., 2000) which uses a 95% statistical parsimony method (Templeton et al., 1992 ). Pairwise genetic distances (within and between the four Acetes species) were calculated based on the Two-parameter Kimura substitution model (K2P).