RESUMEN
BACKGROUND: Mitochondrial genomes have become a powerful tool for studying molecular genetics and phylogeny of mollusks. Currently, the position of Modiolinae within Mytilidae and the taxonomic and phylogenetic relationships within Modiolinae were still controversial. This study focuses on the complete mitochondrial genomes of two species: Modiolus modulaides (Röding, 1798) and Modiolus auriculatus Krauss, 1848, which have not been sequenced before. METHODS AND RESULTS: We assembled and characterized the mitochondrial genomes of M. modulaides and M. auriculatus and then analyzed the phylogenetic relationships. The mitochondrial genomes of M. modulaides and M. auriculatus were 15,422 bp and 16,027 bp, respectively. Both of them were composed of 36 functional genes, including 12 protein-coding genes, 22 transfer RNAs, and 2 ribosomal RNAs. All protein-coding genes showed A + T bias, positive GC skews, and negative AT skews in nucleotide composition. Phylogenetic analysis based on the mitochondrial genomes showed that Modiolinae and Bathymodiolinae clustered together to form a sister relationship. Seven Modiolinae species were divided into two clades: L1 (M. modulaides, M. auriculatus and Modiolus philippinarum Hanley, 1843) and L2 [Modiolus modiolus (Linnaeus, 1758), Modiolus kurilensis Bernard, 1983, Modiolus nipponicus (Oyama, 1950), and Modiolus comptus (Sowerby III, 1915)]. The divergence time of the two clades was approximately 105.75 Ma. Furthermore, the transfer RNA gene rearrangement, longer genetic distance, and greater genetic differentiation were confirmed between the L1 and L2 clades, as well as differences in the external characteristics of the shells of the two clades. CONCLUSIONS: Based on the molecular data, it was speculated that species from the L1 clade might belong to other genera or new genera. This study provides molecular information for further taxonomic and phylogenetic studies of Mytilidae.
Asunto(s)
Genoma Mitocondrial , Filogenia , Genoma Mitocondrial/genética , Animales , ARN de Transferencia/genética , Composición de Base/genética , ARN Ribosómico/genética , ADN Mitocondrial/genética , Evolución Molecular , Análisis de Secuencia de ADN/métodosRESUMEN
Biological invasion is a primary direct driver of biodiversity loss. Recently, owing to exploitation competition with an invasive mussel, Mytella strigata (Hanley, 1843), there has been a drastic decrease in the population of native Perna viridis (Linnaeus, 1758) in several western Pacific regions. In the present study, intestinal microbiota, metabolome, and key digestive enzyme activities were compared between the two competing mussels, M. strigata and P. viridis, to elucidate the differences in intestinal microbiota and metabolic points. We observed that Proteobacteria, Firmicutes, and Bacteroidota were the three predominant bacterial phyla in the two species. The relative abundance of Bacteroidota related to carbohydrate-degrading ability was significantly higher in M. strigata than in P. viridis. Compared to P. viridis, different metabolites including maltose and trehalose were enriched in M. strigata. Lastly, higher carbohydrases activities of alpha-amylase, cellulase, and xylanase were observed in M. strigata than in P. viridis. These differences might play an important role in the adaptation process of M. strigata to the new environment. This study provides important basic knowledge for investigating the competition between M. strigata and P. viridis in terms of food resources utilization.
RESUMEN
Mytella strigata is a highly adaptable invasive alien species that has been established in coastal China since 2014. Mitochondrial DNA (mtDNA) is an important tool for studying the evolution and population genetics of invasive species. In this study, the mitochondrial genome of M. strigata from China was sequenced by Illumina high-throughput sequencing and characterized with 13 protein-coding genes (PCGs). By assessing the selective pressure of 13 PCGs, the nad2 gene had the fastest evolutionary rate and was finally selected for population genetic analysis. A total of 285 nad2 sequences from seven M. strigata populations in China were analyzed and showed obviously T-rich and C-rich characteristics. According to population genetic diversity analysis, all the seven populations had haplotype (gene) diversity (Hd) ≥ 0.5 and nucleotide diversity (Pi) < 0.005. Haplotype networks showed a "star" distribution. Population historical dynamic analyses showed that Fu's Fs and Tajima's D values of all populations were negative except the Qukou (QK) and Beihai (BH) populations. The Zhangzhou (ZJ) and Xiamen (XM) populations were unimodal while the other populations were multimodal. These results suggested that the population of M. strigata in China may have passed the bottleneck period and is currently in a state of population expansion.