Complete mitochondrial genome of the sea cucumber Stichopus sp. and its application in the identification of this species

Abstract

The complete sequence of mitochondrial DNA (mtDNA) from Stichopus sp. (Echinodermata: Holothuroidea: Stichopodidae: Stichopus) was acquired using conventional PCR and long PCR followed by cloning and sequencing. The mtDNA is a circular molecule of 16 similar to 257 similar to bp in length, containing the set of 37 genes, including 13 protein-coding genes (PCGs), 22 tRNA genes and two ribosomal RNA genes. The plus strand consists of 30.9% A, 23.7% C, 16.0% G and 29.3% T bases (AT skew similar to=similar to 0.027; GC skew similar to=similar to-0.194). All 13 PCGs encode a total of 3782 amino acids and all 22 tRNA genes were predicted to be capable of folding into a clover-leaf secondary structure. Intergenetic regions in the mitochondrial genome of Stichopus sp. contain 903 similar to bp in total, with the largest continuous region (674 similar to bp, AT%similar to=similar to 58.6) between tRNA-Thr and tRNA-Pro. Analysis of phylogenetic relationship of family Stichopodidae and genetic distances (species among the family Stichopodidae and species within Stichopus monotuberculatus group) based on the partial cox1 sequence demonstrates that Stichopus sp. from the South China Sea is a member of S. monotuberculatus complex.