The mitochondrial genomes of Cambaroides similis and Procambarus clarkii (Decapoda: Astacidea: Cambaridae): Phylogenetic implications for Reptantia

Abstract

We determined the complete mitochondrial (mt) genome sequences of two northern hemisphere freshwater crayfish species, Cambaroides similis and Procambarus clarkii (Decapoda: Astacidea: Cambaridae). These species have an identical gene order with typical metazoan mt genome compositions. However, their gene arrangement was very distinctive compared to the pan-crustacean ground pattern due to the presence of a long inverted block which included 19 coding genes and a control region (CR). Because the CR was inverted, their nucleotide frequencies showed a reversed strand-specific bias compared to the other decapods. Based on a comparative analysis of mt genome arrangements between southern and northern hemisphere crayfish, and their putative close marine relative (Homarus americanus, a true lobster), we postulated that the ancestor of freshwater crayfish had a typical pan-crustacean mtDNA gene order, similar to its marine relatives. Based on this assumption, we traced the most parsimonious gene rearrangement scenario of the northern hemisphere crayfish. In a phylogenetic study on the infraordinal relationships in reptan decapods, the lineage Lineata (Thalassinidea (Brachyura, Anomura)) was well supported, while the infraorder positions of Achelata and Astacidea remained unidentified.rder with typical metazoan mt genome compositions. However, their gene arrangement was very distinctive compared to the pan-crustacean ground pattern due to the presence of a long inverted block which included 19 coding genes and a control region (CR). Because the CR was inverted, their nucleotide frequencies showed a reversed strand-specific bias compared to the other decapods. Based on a comparative analysis of mt genome arrangements between southern and northern hemisphere crayfish, and their putative close marine relative (Homarus americanus, a true lobster), we postulated that the ancestor of freshwater crayfish had a typical pan-crustacean mt