The complete mitochondrial genome of striped large-eye bream, Gnathodentex aureolineatus (Teleostei, Lethrinidae)

Abstract Striped large-eye bream, Gnathodentex aureolineatus (Lacepède, 1802), is of high economic value and has important ecological functions in coral reefs. However, the genetic information of this species is quite limited, and there is taxonomical difficulty in the family Lethrinidae. Here, we present the complete mitochondrial genome of G. aureolineatus obtained with a long PCR approach and Sanger sequencing. The mitogenome was 16,940 bp in length, consisting of 37 genes (13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes) and two non-coding regions. Both maximum-likelihood and Bayesian inference phylogenetic trees placed the genus Gnathodentex sister to Monotaxis within Lethrinidae. These results contribute toward the taxonomy, conservation, and phylogeny of Lethrinidae.

Striped large-eye bream, Gnathodentex aureolineatus (Lacep ede, 1802), is one of the most common coral reef fishes widely distributed in the Indo-Pacific (Francis and Randall 1993). In China, G. aureolineatus has been recorded in South China Sea coral reefs (Shen et al. 1993;Li et al. 2020;Zhang et al. 2021). As one of the major predators in coral reefs (Carpenter and Allen 1989;Skinner et al. 2020), they usually form aggregations and travel on subtidal reef flats, lagoon platforms, or the upper edge of seaward reefs (Lieske and Myers 1994;Carpenter 1997). However, the genetic information is quite limited for G. aureolineatus, since only several of their nuclear and mitochondrial genes have been used in phylogenetic analyses (Lautredou et al. 2013;Chen and Borsa 2020;Fabian et al. 2021). In addition, the family Lethrinidae has been considered a taxonomically difficult group (Chen and Borsa 2020;Ramesh et al. 2020;Zhang et al. 2021). To establish genetic data for species identification, conservation, and evolutionary clarification, we aimed to sequence the complete mitogenome of G. aureolineatus and constructed the phylogenetic relationships in Lethrinidae.
Three individuals of G. aureolineatus were collected in Triton Island (15 47 0 N 111 12 0 E), Xisha, China, on the same survey approved by the Animal Care and Ethical Committee of the South China Sea Institute of Oceanology, Chinese Academy of Sciences (Guo et al. 2016). According to WORMS (https://www.marinespecies.org/) and FishBase (https://www. fishbase.de/), we conducted species identification, along with the collection of the dorsal muscles for total genomic DNA extraction. Then, three specimens ( Figure 1) were deposited at the South China Sea Tropical Marine Biology Collection, Chinese Academy of Sciences (Minglan Guo, guominglan@ scsio.ac.cn) under voucher numbers: SCSTMBC030980-030982.
Based on the mitogenome sequences of Monotaxis grandoculis (AP009166), Lethrinus laticaudis (KU530221), and L. obsoletus (AP009165) in Lethrinidae, we designed five pairs of primers (Table 1) to amplify the genes using long PCR for Sanger sequencing (Guo et al. 2016). All sequences were assembled using DNAman software, and the overlaid regions were checked using Sanger sequencing with primers designed from the obtained sequences. The assembled mitogenome (GenBank accession no: OM302214 or NC_063714) was annotated using MITOS (Bernt et al. 2013), aligned with Blastn, and checked with tRNAscan-SE (Chan and Lowe 2019). It was 16,940 bp in length, containing 37 genes (13 proteincoding genes, two rRNA genes, and 22 tRNA genes), the origin of light-strand replication (O L ), and the control region (D-loop) ( Table 2). The GenBank file was used to construct the mitogenome circle map on OrganellarGenomeDRAW (https://chlorobox.mpimp-golm.mpg.de/OGDraw.html) ( Figure 2).
The gene arrangement in the mitogenome of G. aureolineatus was identical to that of the above species in Lethrinidae. ND6 and eight tRNA genes were transcribed on the light strand, while the other 28 genes were transcribed on the heavy strand. There were two forms of codon recognition in both tRNA Leu (UUR and CUN) and tRNA Ser (UCN and AGY) (Figure 2). Moreover, intergenic nucleotides occurred between protein-coding genes and/or tRNA genes. Except for COX 1, all protein-coding genes began with the typical start codon ATG. The incomplete stop codon T-appeared in COX2, ND3, ND4, and CYTB, and TA-appeared in ND2, ATP6, and COX3 (Table 2).
This study provides a new mitogenome and phylogenetic relationship in Lethrinidae. The mitogenome will be useful in delimitating problematic groups in taxonomy. These data will offer genome resources for the conservation of G. aureolineatus and a reference for species delimitation and evolutionary research in Lethrinidae.