Abstract:Fragments from mitochondrial gene of Exopalaemon carinicauda sampled from three sites(Haizhou Bay, Xiangshan Bay, and Laizhou Bay) were amplified and sequenced. Sixhundred and fifty eight bp COI fragments were obtained.The T,C, A,G,and A+T mean contents in those fragments were 31.53％,22.63％,27.30％,18.53％, and 58.83％ respectively,which were similar to the results of crustaceans and bivalves.Variable sites, nucleotide diversity and average number of nucleotide differences were calculated to analyze the gene sequence variation.The fixation indices(Fst)analyzed by Analysis of Molecular Variance (AMOVA) of Arlequin Version 3.1 totaled to 0.361 1(P<0.01),indicated significant genetic fixation among three populations. Among them,the genetic differentiation between Xiangshan Bay and Laizhou Bay was the highest,the lowest between Laizhou Bay and Haizhou Bay.The molecular phylogenetic tree constructed by NJ method using software MEGA 4.0 to study molecular phylogeny of several species of the by Palaemonidae. The phylogenetic tree showed that different haplotypes of E.carinicauda were more closely related to Palaemon and Palaemonetes than to Macrobrachium
