The complete mitochondrial genome sequencing of Anisakis simplex isolated from Anoplopoma fimbria

Abstract

In this study, zoonotic Anisakis simplex was isolated and identified from the outermost layer of the stomach of diseased Anoplopoma fimbria at an industrial farm in Liaoning, North China (122.1842 E, 39.2616 N). With the completion of A. simplex mitochondrial genome sequencing, the full-length mitochondrial genome of A. simplex was assembled and analyzed. All results indicate that the complete mitochondrial genome of A. simplex was 13,899 bp. There were 20 tRNAs and 12 protein-coding genes (PCGs), and two rRNA all located at the heavy (H) strand. Besides, the phylogenetic tree of 19 A. simplex isolated from different host species was constructed. The results showed that A. simplex isolated from A. fimbria was clustered with Oncorhynchus nerka isolate in a clade. To sum up, our research results would further provide essential data for systematics and evolution study of A. simplex.

Anisakis simplex, belonged to order Ascaridata, family Anisakinae, and genus Anisakis, was usually parasitic in the viscera or muscle tissue of much teleost fish. Healthy individuals who eat raw, half-cooked or pickled marine fish that infected by A. simplex could appear some gastrointestinal symptoms, such as abdominal pain, nausea, diarrhea and vomiting (Daschner and Pascual 2005). At present, the Chinese government has already listed A. simplex as the second-class animal infectious disease pathogen in List of Monitored Infectious Disease in-law.

Anoplopoma fimbria, a cold-water economic fish that lived in the deep sea, and belonged to the phyla Actinopterygii, order Scorpaeniformes, family Anoplopomatidae, genus Anoplopoma, distributed in the Arctic Ocean, and North Pacific coast, including the North American coast from northern Mexico to the Bering Sea, and the Asian coastal regions from the Kamchatka Peninsula to the northeastern coast of Japan (Rondeau et al. 2013; Xiong et al., 2016). In 2013, the A. fimbria was introduced and successfully bred in North China. However, research reports on the disease of A. fimbria were still rare.

In the current study, A. simplex was isolated and identified from the outermost layer of the stomach of diseased A. fimbria, at an industrial farm in Liaoning, North China (122.1842 E, 39.2616 N). With the completion of A. simplex mitochondrial genome sequencing by SC Gene Company (Guangzhou, China) via Illumina MiSeq Next-generation sequencing technique, the full-length mitochondrial genome of H. okamotoi was assembled and submitted to the GenBank database (No. MK820679). Meanwhile, mitochondrial DNA and specimen of A. simplex (Number: AFAS01) were preserved and stored in the Dalian Key Laboratory of Marine Animal Disease Control and Prevention, Dalian Ocean University. All analytical results indicate that the complete mitochondrial genome of A. simplex was 13,899 bp. There were 20 tRNAs (tRNA-Lys, tRNA-Ser, tRNA-Ile, tRNA-Arg, tRNA-Gln, tRNA-Phe, tRNA-Leu, tRNA-Thr, tRNA-Cys, tRNA-Met, tRNA-Asp, tRNA-Gly, tRNA-His, tRNA-Ala, tRNA-Pro, tRNA-Val, tRNA-Trp, tRNA-Glu, tRNA-Asn, and tRNA-Tyr), 12 protein-coding genes (PCGs), and two rRNA (all located at the heavy (H) strand. Among these PCGs, nine genes (nd1, atp6, nd2, cox3, nd4, cox1, cox2, nd3, and nd6) were with start codon TTG, the rest PCGs cytb, nd5, and nd4l used the start codon ATT. Besides, 5 PCGs (nd1, atp6, nd2, nd4, nd6 used the stop codon TAA, and two genes (nd3 and cox2) were with the stop codon TAG.

Based on sequences of 12 PCGs (nd1, atp6, nd2, cytb, cox3, nd4, cox1, cox2, nd3, nd5, nd6, nd4l), the phylogenetic tree of 19 A. simplex isolated from different host species was constructed by Maximum Likelihood method. The results showed that A. simplex isolated from A. fimbria was clustered with Oncorhynchus nerka isolate in a clade (Figure 1). Moreover, A. simplex, Anisakis pegreffii, and Anisakis berlandi were clearly divided into different groups (Figure 1).

Figure 1.

Phylogeny of Anisakis simplex phylogenetic tree based on nucleotide sequences of PCGs located in the mitogenome. The number of the branches denoted NJ/MP/ML posterior probabilities.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.