The complete mitogenome of Hong Kong paradise fish (Macropodus hongkongensis), an endemic freshwater fish in South China.

The first complete mitogenome of Hong Kong paradise fish (Macropodus hongkongensis) was determined in this study. The assembled mitogenome is 16,494 bp and consisted of 13 protein-coding genes, 22 tRNAs, 2 rRNAs, and a control region. Nucleotide composition of the complete mitogenome is 30.6% A, 24.8% C, 14.8% G, and 29.8% T, with an A + T bias of 60.4%. The maximum-likelihood tree based on 13 protein-coding genes showed that M. erythropterus was the closest related species to M. hongkongensis.

The Hong Kong paradise fish (Macropodus hongkongensis) is a tropical freshwater fish, which belongs to the genus Macropodus within the family Osphronemidae (Chan et al. 2008; Winstanley and Clements 2008). This fish is only found in Hong Kong, eastern Guangdong and Fujian Provinces, and its native habitats are marshes and slow-moving streams (Chan et al. 2008; Winstanley and Clements 2008). The wild population of M. hongkongensis is suspected to be in decline owing to development (Chan et al. 2008; Dudgeon 2014). Until now, there are a few reports on evolution and conservation genetics of this fish.

In this study, the complete mitogenome of M. hongkongensis was determined. A specimen of M. hongkongensis was collected from the slow-moving stream in Siyun Village of Zhaiwu Town, Heshan County, Guangdong Province (22.70°N, 112.68°E). The specimen was deposited in the Zoological Museum of Nanjing Forestry University (Accession GDHS201905). Total DNA was extracted following the standard phenol-chloroform extraction procedure (Sambrook and Russell 2001). A set of primers was designed based on the complete mitochondrial genome sequences of M. erythropterus (GenBank accession KU215670.1), M. opercularis (GenBank accession KM588227.1), and M. ocellatus (GenBank accession KJ813282.1). Both PCR amplification and Sanger sequencing were performed using these primers. The complete mitogenome of M. hongkongensis is 16,494 bp in length (GenBank accession MN128300), containing 13 protein-coding genes, 22 tRNAs, 2 rRNAs, and a control region. Most elements are transcribed on the heavy strand, except for ND6 gene and 8 tRNAs (Gln, Ala, Asn, Cys, Tyr, Ser, Glu, Pro) which are transcribed on the light strand. The overall base composition is 30.6% A, 24.8% C, 14.8% G, and 29.8% T, with an A + T bias of 60.4%. The mitochondrial features of M. hongkongensis are identical to other Macropodus fishes (Mu et al. 2015; Xu et al. 2016; Yu et al. 2016).

Maximum-Likelihood phylogeny of M. hongkongensis and other 14 Osphronemidae fishes based on 13 protein-coding genes were reconstructed, using Siniperca chuatsi as an outgroup (Figure 1). The phylogenetic analysis showed that all fishes of the genus Macropodus were clustered into a group. Macropodus erythropterus was the closest related species to M. hongkongensis with high bootstrap support value. The complete mitogenome reported here will provide a useful resource for the conservation genetics of M. hongkongensis as well as for the phylogenetic studies for the genus Macropodus.

Figure 1.

Maximum-likelihood phylogenetic tree of 15 Osphronemidae fishes based on 13 protein-coding genes. Siniperca chuatsi was set as an outgroup. Bootstrap support values are shown on the nodes and numbers following scientific names are GenBank accessions.