Abstract
Phymorhynchus is a genus of deep-sea snails that are most distributed in hydrothermal vent or cold seep environments. In this study, we presented the complete mitochondrial genome of P. buccinoides, a cold seep snail from the South China Sea. It is the first mitochondrial genome of a cold seep member of the superfamily Conoidea. The mitochondrial genome is 15,764 bp in length, and contains 13 protein-coding genes (PCGs), 2 rRNA genes, and 22 tRNA genes. These genes are encoded on the positive strand, except for 8 tRNA genes that are encoded on the negative strand. The start codon ATG and 3 types of stop codons, TAA, TAG and the truncated termination codon T, are used in the 13 PCGs. All 13 PCGs in the 26 species of Conoidea share the same gene order, while several tRNA genes have been translocated. Phylogenetic analysis revealed that P. buccinoides clustered with Typhlosyrinx sp., Eubela sp., and Phymorhynchus sp., forming the Raphitomidae clade, with high support values. Positive selection analysis showed that a residue located in atp6 (18 S) was identified as the positively selected site with high posterior probabilities, suggesting potential adaption to the cold seep environment. Overall, our data will provide a useful resource on the evolutionary adaptation of cold seep snails for future studies.
Highlights
Conoidea are venomous marine gastropods in Neogastropoda [1, 2], which are found in all oceans, from the tropics to the poles, and from shallow waters to abyssal depths [3]
We have reported the mitochondrial genome of Phymorhynchus buccinoides Okutani, Fujikura & Sasaki, 1993 in the family Raphitomidae, a gastropod collected from the Haima cold seeps in the South China Sea at depth of 1388 m
The genome comprises 37 genes, including 13 protein-coding genes (PCGs), 2 rRNA genes, and 22 transfer RNA genes (tRNAs) genes
Summary
Conoidea are venomous marine gastropods in Neogastropoda [1, 2], which are found in all oceans, from the tropics to the poles, and from shallow waters to abyssal depths [3]. Phylogenetic relationships and evolution of Conoidea are very challenging because of its high diversity [9]. In this context, the complete mitochondrial genome analysis can bring new information to the phylogenetic analysis of Conoidea. Different positively selected genes are detected between this and previous studies [e.g, 16], which may be caused by the fact that different animal groups might have different adaptation mechanisms, or that the results of positive selection are probably inaccurate due to limited species. More species from cold seeps and other reducing environments such as hydrothermal vents are required to understand the mitochondrial adaptation for this important gastropod group
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