Complete mitochondrial genome of the fish leech Zeylanicobdella arugamensis

Abstract

The complete mitochondrial genome of the fish leech Zeylanicobdella arugamensis from China has been determined for the first time in this study. It was 16,161 bp in length and consisted of 22 tRNA genes, two rRNA genes, 13 protein-coding genes (PCGs), and one control region. The nucleotide base content of Z. arugamensis mitogenome was 35.5% A, 10.4% C, 10.4% G, and 43.7% T. Start codon ATG was used in PCGs, while most of the termination codons are incomplete T or TA. The tRNA genes were ranged from 59 bp (tRNA-Arg and tRNA-Glu) to 69 bp (tRNA-Gln and tRNA-Cys) in length. The phylogenetic tree was constructed and suggested that Z. arugamensis has closer relationship to the Poecilobdella manillensis, Erpobdella octoculata, Hirudo hipponia, Whitmania acranulata, Whitmania pigra, Whitmania Laevis, Hirudo verbaba, and Hirudo medicinalis, and that they constitute a sister group.

Keywords:

• Mitochondrial genome
• Zeylanicobdella arugamensis

Parasitic infestation is one of the major problem for Asian sea bass cultured in cages (Leong et al. 2006). Marine leeches Zeylanicobdella arugamensis was considered to be the most common parasites in cultured marine fish. The first report of Z. arugamensis was from tank-reared grouper Epinephelus coioides in the Philippines (De Silva 1963), and later infections by Z. arugamensis have been reported in Sri Lanka, Malaysia, Singapore, India and Japan (De Silva and Fernando 1965; Sanjeeva et al. 1977; Cruz-Lacierda et al. 2000; Nagasawa and Uyeno 2009). In this study, the complete mitochondrial genome of the fish leech Z. arugamensis from China was sequenced for the first time, aiming to contribute to the species identification and phylogenetic study. The specimen was obtained from the grouper Epinephelus fuscoguttatus reared in Qionghai research base of Hainan Academy of Ocean and Fisheries Sciences (E110.68, N19.37). The specimen of Z. arugamensis was stored in Qionghai research Base and preserved in 95% ethanol.

The whole mitochondrial genome of Z. arugamensis is 16,161 bp in length (GenBank Accession number KY474378). It consists of 22 tRNA genes, two rRNA genes, 13 protein-coding genes (PCGs), and one control region. The nucleotide base content of Z. arugamensis mitogenome was 35.5% A, 10.4% C, 10.4% G, and 43.7% T. The 79.2% of (A + T) showed great preference to AT.

The mitochondrial genome of Z. arugamensis contains 22 tRNA genes varying from 59 bp to 69 bp in length. The 12s rRNA is 738 bp in length and located between tRNA-Met and tRNA-Val, and the 16s rRNA is 1155 bp in length, located between tRNA-Val and tRNA-Leu1. The mtDNA of Z. arugamensis consists of 13 PCGs, and all these genes begin with a standard ATG start codon. Most of the termination codons are incomplete T or TA, except for CYTP, ND4L, and ND4, which use TAA as stop codon. The control region is 1670 bp in length located between tRNA-Arg and tRNA-His.

The phylogenetic trees were construction based on the mitochondrial genome sequence of 14 fish leech (Clitellata: Hirudinea) species by Maximum Likelihood (ML) method. The result (Figure 1) has suggested that Z. arugamensis has closer relationship to the Poecilobdella manillensis, Erpobdella octoculata, Hirudo hipponia, Whitmania acranulata, Whitmania pigra, Whitmania Laevis, Hirudo verbaba, and Hirudo medicinalis, and that they constitute a sister group.

Figure 1. Phylogenetic tree derived from Z. arugamensis and the other leech’ mtDNA genome nucleotide sequences.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Major S&T projects of Hainan Province (ZDKJ2016013).