Complete mitochondrial genome and phylogenetic analysis of the caddisfly Neucentropus mandjuricus (Trichoptera: Polycentropodidae)

Abstract

We have sequenced and annotated the complete mitogenome of Neucentropus mandjuricus Martynov, 1907, a monotypic genus of Polycentropodidae with controversial taxonomic status. The complete mitogenome of N. mandjuricus is 15,020 bp in length, including 13 protein-coding genes, two ribosomal genes, 22 transfer RNA genes, and a non-coding control region. The maximum-likelihood and Bayesian’s inference trees based on 13 protein-coding genes of 23 trichopteran species show that N. mandjuricus clusters together with the other polycentropodid Plectrocnemia sp. with high support value. This study provides a basis for further study on mitogenome and phylogenetics of the Polycentropodidae.

Introduction

The Polycentropodidae is a large family among Trichoptera and distributed worldwide, consisting of 30 genera in three subfamilies (Morse 2022). Neucentropus Martynov, 1907 is a monotypic genus of Polycentropodidae, including only one species: Neucentropus mandjuricus Martynov, 1907. However, the taxonomy status of Neucentropus has been controversial as the intraspecific variations widely existed in the wing and external genitalia (Li et al. 1998). The phylogenetic analysis based on three protein-coding genes indicated that Neucentropus combines with Neureclipsis and locates in the most basal branch of Polycentropodidae (Johanson et al. 2012). In this study, we have sequenced and annotated the complete mitogenome of Neucentropus mandjuricus, aiming to provide more molecular data for phylogenetic analysis of Polycentropodidae.

Materials and methods

Specimens of N. mandjuricus were collected from Xichuan County, Henan Province, China (32°40′25″ N, 111°43′1″ E) in June 2021 (Figure 1), preserved in pure ethanol and transferred to laboratory refrigerator at Nanyang Normal University, Nanyang, China (specimen voucher: NYNU-N1, Chao Yue, yuechaomail@163.com). Whole-genome sequencing of N. mandjuricus was performed by Novogene (Beijing, China) using Illumina NovaSeq 6000 platform, the clean reads were subjected to MitoZ v3.3 (Meng et al. 2019) pipeline for mitogenome assembly and annotation. The complete mitogenome of N. mandjuricus has been deposited in GenBank under accession number OK509078. The circular mitogenome map was generated using OGDRAW v1.3.1 (Greiner et al. 2019).

Figure 1.

Male adult of Neucentropus mandjuricus.

Results and discussion

The complete mitogenome of N. mandjuricus is 15,020 bp in length, with double circular strands consisting of 13 protein-coding genes (PCGs), two ribosomal genes (rRNA), 22 transfer RNA (tRNA) genes, and a non-coding control region (Figure 2). The mitogenome exhibits AT-bias, with the AT content of 81% (A = 37%, T = 44%, C = 6.3%, G = 12.6%). The total length of 13 PCGs is 10,922 bp, accounting for 72.72% of the whole genome. All PCGs are initiated with ATN codons, as four PCGs (nad3, nad4L, nad5, and nad6) with ATT, four (atp6, cytb, nad1, and nad4) with ATG, four (nad2, cox1, cox3, and atp8) with ATA, and cox2 with ATC. Nad2, cox1, and cox2 use the truncated stop codon (T), while the other PCGs all end with TAA. The 22 tRNA genes vary from 58 bp (trnS) to 72 bp (trnK and trnL). Two rRNA genes (rrn12 and rrn16), located at trnF/control region and trnV/nad1, are 622 bp and 1368 bp in length, respectively. Comparative mitogenome analyses between N. mandjuricus and Plectrocnemia sp. (another Polycentropodinae with complete mitogenome available at GenBank under accession number MW413804) reveals significant collinearity for 13 PCGs. Gene rearrangement is also found for some tRNA genes: trnG is located between trnQ and trnL in N. mandjuricus, whereas in Plectrocnemia sp. it is between trnH and control region.

Figure 2.

The circular mitogenome map of Neucentropus mandjuricus.

For phylogenetic analysis, the coding sequences of 13 PCGs from 23 Trichoptera, along with a Lepidoptera species Thitarodes damxungensis (Yang, 1995) as an outgroup, were individually aligned based on the codons using PAL2NAL v14 (Suyama et al. 2006), and concatenated to form a single dataset. The maximum-likelihood (ML) and Bayesian’s inference (BI) trees were then generated by RAxML-NG v1.1.0 (Kozlov et al. 2019) and MrBayes v3.2.7 (Ronquist et al. 2012), respectively (Figure 3). The result shows that N. mandjuricus forms the sister group to Plectrocnemia sp. with high support value (BS = 100, PP = 1). Polycentropodidae and Stenopsychidae have close relationship, forming the sister group to other Annulipalpia. Our study provides more molecular data for further research on evolutionary relationships of Polycentropodidae.

Figure 3.

Maximum-likelihood (ML) and Bayesian’s inference (BI) phylogenetic tree generated using concatenated coding sequences of 13 mitochondrial PCGs from 23 trichopteran species, and a Lepidoptera species Thitarodes damxungensis as an outgroup. Support values beside nodes represent bootstrap support and posterior probability.

Funding Statement

This work was supported by the National Natural Science Foundation of China [Grant No. 31672346]; the Special Scientific Research Project of Nanyang Normal University [Grant No. 70648 and 70649].

Author contributions

Conceived and designed the study: Chao Yue. Performed the experiments: Zhen Li. Analyzed the data: Na Ma and Ting Lei. Draft the manuscript: Na Ma and Chao Yue. Revised the manuscript: Ting Lei. Final approval of the version to be published: Ting Lei and Chao Yue. All authors agreed to be accountable for all aspects of the work.

Ethics statement

The collected insect samples are not protected by regulations or law and not required an ethical review by the Statement Animal Experiment Committee.

Disclosure statement

The authors report no conflict of interest.

Data availability statement

The genome sequence data that support the findings of this study are openly available in GenBank of NCBI at https://www.ncbi.nlm.nih.gov under the accession no. OK509078. The associated BioProject, SRA, and Bio-Sample numbers are PRJNA858192, SRP386152, and SAMN29673587, respectively.