The complete mitochondrial genome of the roosterfish Nematistius pectoralis Gill 1862: Purifying selection in protein coding genes, organization of the control region, and insights into family-level phylogenomic relationships in the recently erected order Carangiformes.

The roosterfish Nematistius pectoralis is considered as one of the most magnificent sportfishes worldwide. This study developed the first genomic resource for this trophy-fish that is heavily targeted by the fly-fishing industry. The complete mitochondrial genome of N. pectoralis was assembled using short read sequences and analyzed in detail. The mitochondrial genome of N. pectoralis is 16,537 bp in length and comprises 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (12S and 16S), and 22 transfer RNA genes. A long intergenic space 770 bp in length was assumed to be the d-loop or Control Region (CR). Most of the PCGs and tRNA genes are encoded in the l-strand. All PCGs are under purifying selection and atp8 and nad6 experienced the least selective pressure. All tRNAs exhibit a cloverleaf secondary structure except tRNA-Serine 1 that lacked the d-arm loop. The d-loop of N. pectoralis exhibits three domains commonly described in other fishes; extended terminal associated sequences (ETAS), central, and conserved sequence block (CSB). A ML phylogenetic reconstruction of the newly recognized order Carangiformes based on all 13 mitochondrial PCGs did not support the monophyly of this clade but recognized several families as monophyletic, including Bothidae, Carangidae, Istiophoridae, Latidae, Paralichthyidae, Polynemidae, and Rhombosoleidae. Nematistius pectoralis was sister to a clade composed of Toxotes chatareus (fam. Toxotidae) + Lactarius lactarius (fam. Lactariidae). This genomic resource developed for N. pectoralis will aid in improving our understanding of the population genomics of and strengthen conservation and management strategies in this remarkable trophy-fish.

Genome Survey Sequencing of an Iconic 'Trophy' Sportfish, the Roosterfish Nematistius pectoralis: Genome Size, Repetitive Elements, Nuclear RNA Gene Operon, and Microsatellite Discovery.

The 'Pez Gallo' or the Roosterfish, Nematistius pectoralis, is an ecologically relevant species in the shallow water soft-bottom environments and a target of a most lucrative recreational sport fishery in the Central Eastern Pacific Ocean. According to the International Union for Conservation of Nature, N. pectoralis is assessed globally as Data Deficient. Using low-coverage short Illumina 300 bp pair-end reads sequencing, this study reports, for the first time, the genome size, single/low-copy genome content, and nuclear repetitive elements, including the 45S rRNA DNA operon and microsatellites, in N. pectoralis. The haploid genome size estimated using a k-mer approach was 816.04 Mbp, which is within the range previously reported for other representatives of the Carangiformes order. Single/low-copy genome content (63%) was relatively high. A large portion of repetitive sequences could not be assigned to the known repeat element families. Considering only annotated repetitive elements, the most common were classified as Satellite DNA which were considerably more abundant than Class I-Long Interspersed Nuclear Elements and Class I-LTR Retroviral elements. The nuclear ribosomal operon in N. pectoralis consists of, in the following order: a 5' ETS (length = 948 bp), ssrDNA (1835 bp), ITS1 (724 bp), a 5.8S rDNA (158 bp), ITS2 (508 bp), lsrDNA (3924 bp), and a 3' ETS (32 bp). A total of 44 SSRs were identified. These newly developed genomic resources are most relevant for improving the understanding of biology, developing conservation plans, and managing the fishery of the iconic N. pectoralis.