COMPLETE MITOCHONDRIAL GENOME SEQUENCING OF LOTTIA LUCHUANA AND PHYLOGENTIC ANALYSIS OF THE FAMILY LOTTIIDAE

The family Lottiidae (Gray 1840) is one of the most primitive gastropods in existence, and the mitochondrial gene (mitogenome) have been used to analyze the phylogenetic relationship in Patellogastropoda, but the complete mitogenome of some species in Lottiidae have not been mentioned. In this study, we obtained the complete mitogenome of Lottia luchuana by next-generation sequencing technology, and analyzed the basic characteristics of its genome, and we found that it contains 38 genes, including 13 protein-coding genes (PCGs), two RNAs, 23 tRNAs, one more trnM than most Gastropoda species. The base content analysis showed that T base content was the highest at 32.34%, and C base content was the lowest at 14.99%. Gly, Phe, Ser and Val were the four most commonly used amino acids, UUA (Leu2), UUU (Phe), CCU (Pro) and AGA (Ser2) are the four most commonly used codons. We selected the mitogenomes of Lottiidae 13 species for selection pressure analysis and all PCGs had a K_a/K_s ratio below 1 and were subjected to purification selection. In addition, a phylogenetic tree was constructed by combining the 13 PCGs of the mitogenomes of six subclass under Gastropoda, and the Lottiidae is a monophyletic group, and has a relatively close relationship with Patellidae, but the results of this analysis are still affected by the attraction of long branches, so that the branch of Patellogastropoda is divided into two parts, but with the increase of species richness, it may gradually resist the attraction of long branches. A linear sequence comparison of the mitogenomes of all species of Patellogastropoda showed that Lottiidae showed the most extensive irregular rearrangement in Patellogastropoda, and also changed in the number of tRNAs. From the reconstructed chronological map of the divergence time of Patellogastropoda, it is concluded that the differentiation of limpet first occurred in the Jurassic period of the Mesozoic, and a large number of species diverged rapidly in the Cenozoic. These results will help people better understand the phylogenetic relationship between limpet, as well as the evolutionary relationship and evolutionary status of each subclass within the Gastropoda, provide more reference for species classification.