Mitochondrial phylogeny of Chinese barred species of the cyprinid genus Acrossocheilus Oshima, 1919 (Teleostei: Cypriniformes) and its taxonomic implications

In this study, we sequenced and characterized the complete mitochondrial genome of Acorssocheilus spinifer, an endemic stream-dwelling cyprinid species from South China first described in 2006. The mitogenome is 16,591 bp in length and contains the standard set of 37 genes (13 protein-coding genes, 22 tRNA genes, 2 rRNA genes) plus a control region. The genome exhibits typical cyprinid characteristics, with most genes encoded on the H-strand and a nucleotide composition biased toward A + T (55.9%). All tRNA genes display the typical cloverleaf secondary structure, except for tRNA^Ser (GCU), which lacks the dihydrouridine (DHU) arm. Phylogenetic analysis using complete mitogenomes from 14 Acrossocheilus species revealed that 12 species form a monophyletic assemblage with three distinct clades. Within this framework, A. spinifer clusters closely with A. beijiangensis, supporting previous morphological observations. Our findings provide valuable genetic data for further taxonomic refinement and conservation efforts for Chinese barred species of Cyprinidae.

Acorssocheilus beijiangensis is an endemic south China stream-dwelling cyprinid species. Its complete mitochondrial genome is 16,596 bp in length, consisting of 13 protein-coding genes, 22 tRNA genes (ranging from 67 bp in tRNACys to 76 bp in tRNALeu and tRNALys), two rRNA genes (959 bp in 12S rRNA and 1683 bp in 16S rRNA), and one control region (937 bp). Its overall base composition is A: 31.1%, C: 27.9%, G: 16.2%, and T: 124.8%. The complete mitogenome of the Chinese barred species of Cyprinidae could provide a basic data for further phylogenetics analysis.

Tachysurus wuyueensis, new species, is described from the Qiantang-Jiang Basin, situated in Suichang County, Zhejiang Province and Xiuning County, Anhui Province, southeast China. The coastal basin drains into the East China Sea. The new species belongs to the T. pratti-T. truncatus group within the genus Tachysurus defined by having a smooth anterior margin of the pectoral-fin spine, short maxillary barbels not extending beyond the base of the pectoral-fin spine, short dorsal spine not exceeding two thirds of head length and an emarginated caudal fin. This new species is distinct from all other species of this group, Tachysurus pratti (Gunther, 1892), T. truncatus (Regan 1913), T. gracilis (Li, Chen & Chan, 2005) and T. brachyrhabdion (Cheng, Ishihara & Zhang, 2008), in having a shorter prepelvic body (length 40.0–46.4% of SL vs. 45.8–54.8%). It further differs from T. pratti, T. truncatus and T. gracilis in having more vertebrae (45–47 vs. 37–44) and more anal fin rays (21–25 vs. 14–20), from T. brachyrhabdion in having a more slender body (depth 10.1–13.5% of HL vs. 13.1–17.6%). Molecular phylogeny, based on the mitochondrial cytochrome b (cyt. b) gene confirms the validity of T. wuyueensis and the T. pratti-T. truncatus group. Furthermore, this study addresses the diagnostic traits distinguishing the T. pratti-T. truncatus group from the T. tenuis-T. crassilabris group which have historically been treated as a single species group due to morphological similarities.

Acrossocheilus jishouensis is an endemic south China stream-dwelling cyprinid species. Its complete mitochondrial genome is 16,587 bp in length, consisting of 13 protein-coding genes, 22 tRNA genes (ranging from 67 bp in tRNA^Cys to 76 bp in tRNA^Leu and tRNA^Lys), two rRNA genes (956 bp in 12S rRNA and 1673 bp in 16S rRNA), and one control region (942 bp). Its overall base composition is A: 31.2%, C: 27.6%, G: 16.2%, and T: 25.1%. The complete mitogenome of the Chinese barred species of Cpynidae could provide a basic data for further phylogenetics analysis.