The complete sequence of the mitochondrial genome of the crustacean Penaeus monodon: Are malacostracan crustaceans more closely related to insects than to branchiopods?

The complete sequence of the mitochondrial genome of the giant tiger prawn, Penaeus monodon (Arthropoda, Crustacea, Malacostraca), is presented. The g ene content and gene order are identical to those observed in Drosophila ya kuba. The overall AT composition is lower than that observed in the known i nsect mitochondrial genomes, but higher than that observed in the other two crustaceans for which complete mitochondrial sequence is available. Analys is of the effect of nucleotide bias on codon composition across the Arthrop oda reveals a trend with the crustaceans represented showing the lowest pro portion of AT-rich codons in mitochondrial protein genes. Phylogenetic anal ysis among arthropods using concatenated protein-coding sequences provides further support for the possibility that Crustacea are paraphyletic. Furthe rmore, in contrast to data from the nuclear gene EF1 alpha, the first compl ete sequence of a malacostracan mitochondrial genome supports the possibili ty that Malacostraca are more closely related to Insecta than to Branchiopo da.