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Research Article
New species, a new combination, and DNA barcodes of Parachironomus Lenz, 1921 (Diptera, Chironomidae)
expand article infoWen-Bin Liu‡, Ying Wang‡, Kang-Zhu Zhao‡, Cheng-Yan Wang‡, Jun-Yu Zhang‡, Chun-Cai Yan‡, Xiao-Long Lin§
‡ Tianjin Normal University, Tianjin, China
§ Shanghai Ocean University, Shanghai, China

Corresponding author: Chun-Cai Yan ( skyycc@mail.tjnu.edu.cn )

Corresponding author: Xiao-Long Lin ( lin880224@gmail.com )

Academic editor: Fabio Laurindo da Silva
© 2023 Wen-Bin Liu, Ying Wang, Kang-Zhu Zhao, Cheng-Yan Wang, Jun-Yu Zhang, Chun-Cai Yan, Xiao-Long Lin.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Liu W-B, Wang Y, Zhao K-Z, Wang C-Y, Zhang J-Y, Yan C-C, Lin X-L (2023) New species, a new combination, and DNA barcodes of Parachironomus Lenz, 1921 (Diptera, Chironomidae). ZooKeys 1153: 121-140. https://doi.org/10.3897/zookeys.1153.98542
ZooBank: urn:lsid:zoobank.org:pub:33E8B084-33BA-4CD7-8021-7AD989C2E826
Open Access

Abstract

The genus Parachironomus has a cosmopolitan distribution including 85 valid described species worldwide. Species records and studies of the genus in the Tibetan Plateau are scarce. In this study, the genus Parachironomus from China is revised and two new species, Parachironomus wangi Liu & Lin, sp. nov. and Parachironomus nankaiensis Liu & Lin, sp. nov., are described based on adult morphology and molecular data. Paracladopelma demissum Yan, Wang & Bu is placed in the genus Parachironomus as a new combination. A neighbor-joining tree was reconstructed based on all known Parachironomus COI DNA barcodes. A key to adult males of the genus Parachironomus from China is also provided.

Keywords

COI, new combination, new species, taxonomy, Tibetan Plateau

Introduction

The genus Parachironomus was erected by Lenz (1921) based on the characters of larvae and pupae with Chironomus cryptotomus Kieffer, 1915 as type species. Subsequently, the genus was studied by a number of authors in different life stages and geographical areas (Edwards 1929; Townes 1945; Cranston et al. 1989; Sæther and Spies 2013). Larvae of Parachironomus can be found in a variety of habitats, such as standing and flowing waters, soft sediments, or within aquatic macrophytes, while others are endo- or ectoparasites on snails (Orel 2017). Among the Harnischia generic group, members of Parachironomus can separated from the similar genus Demicryptochironomus Lenz by the extended superior volsella with several distal setae always arising from distinct pits, and the inferior volsella with a pointed or blunt caudal projection (Yan et al. 2015). To date, 85 valid species have been reported worldwide (Lehmann 1970; Ashe and Cranston 1990; Kikuchi and Sasa 1990; Oliver et al. 1990; Sæther et al. 2000; Wang 2000; Sasa et al. 2001; Sasa and Tanaka 2001; Makarchenko et al. 2005; Spies 2008; Trivinho-Strixino et al. 2010; Yan et al. 2015; Orel 2017).

The DNA barcodes corresponding to the 658-bp fragment of the mitochondrial gene cytochrome c oxidase I (COI) has been identified as the core of a global bio-identification system at the species level (Hebert et al. 2003a, b). DNA barcodes also proved to be useful in the delimitation of non-biting midge species and has provided important evidence to confirm new species (Anderson et al. 2013; Lin et al. 2015, 2021; Giłka et al. 2018; Liu et al. 2021).

The Tibetan Plateau is located in southwest China, with a vast territory and diverse terrain. The Tibetan Plateau is one of the most important areas of biodiversity in the world because of its unique environmental and regional units, which breed unique biological communities and many unique and rare wild animals and plants. Some interesting species were discovered during the investigations of insect diversity in the Tibetan Plateau. In this paper, one new combination and two new species are proposed and described. The partial COI sequences of species in Parachironomus with DNA barcode analysis is conducted. A key to the known Chinese adult males of the genus is presented.

Materials and methods

The examined specimens were caught using sweep net and light trap, stored in the dark at 4 °C, and preserved in 85% ethanol before molecular and morphological analyses. Genomic DNA was extracted from the thorax and leg using a Qiagen DNA Blood and Tissue Kit at Tianjin Normal University, Tianjin, China (TJNU), following the standard protocol except for the final elution volume of 100 µl. After DNA extraction, the exoskeleton of each specimen was mounted in Euparal on a microscope slide together with the corresponding antennae, legs, wing, and abdomen, following the procedures outlined by Sæther (1969). Morphological terminology follows Sæther (1980).

The color pattern of all species is described based on the specimen preserved in ethanol. Digital photographs of slide-mounted specimens were taken with a 300-dpi resolution using Nikon Eclipse 80i with Nikon Digital Sight DS-Fil camera at TJNU.

The universal primers LCO1490 and HCO2198 (Folmer et al. 1994) were adopted to amplify the standard 658-bp mitochondrial COI barcode region. Polymerase chain reaction (PCR) amplifications followed Song et al. (2018) and were conducted in a 25 µl volume including 12.5 µl 2× Es Taq MasterMix (CoWin Biotech Co., Beijing, China), 0.625 µl of each primer, 2 µl of template DNA, and 9.25 µl of deionized H2O. PCR products were electrophoresed in 1.0% agarose gel, purified, and sequenced in both directions at Beijing Genomics Institute Co. Ltd., Beijing, China.

Raw sequences were assembled and edited in Geneious Prime 2020 (Biomatters Ltd., Auckland, New Zealand). Alignment of the sequences was carried out using the MUSCLE (Edgar 2004) algorithm on amino acids in MEGA v. 7.0 (Kumar et al. 2016). Some published DNA barcodes of Parachironomus were downloaded from the Barcode of Life Data Systems (BOLD) (Ratnasingham and Hebert 2013). Before phylogenetic analysis, nucleotide substitution saturation analysis of gene sequences was performed by DAMBE version 6 (Xia 2017). The pairwise distances were calculated using the Kimura 2-Parameter (K2P) substitution model in MEGA. The neighbor-joining (NJ) tree was constructed using the K2P substitution model, 1000 bootstrap replicates, and the “pairwise deletion” option for missing data in MEGA. Novel sequences, trace-files, and metadata of the new species were uploaded to the BOLD platform.

In this study, the partial COI sequences of Parachironomus were submitted to online ABGD web interface (https://bioinfo.mnhn.fr/abi/public/abgd/abgdweb.html). We used the K2P nucleotide substitution model. The prior intraspecific divergence was set at between 0.001 and 0.1. The minimum relative gap width was 1.0 and other parameters were defaulted.

The holotype of two new species is deposited at the College of Fisheries and Life Science, Shanghai Ocean University (SHOU) and College of Life Sciences, Tianjin Normal University, Tianjin, China (TJNU).

Results

DNA barcode analysis

In this study, five COI sequences were obtained, and 19 COI sequences of Parachironomus were downloaded from BOLD, totaling 24 COI sequences. All sequences could be translated successfully into amino acids without indels and stop codons. MEGA analysis showed that the average total length of the sequence was 658 bp, and that there were 427 conserved sites, 231 variable sites, 196 parsimony informative sites, and 35 singleton sites. The mean nucleotide base compositions were 27.1% A, 17.9% C, 16.2% G, and 38.8% T for COI genes (Table 1). The ratio of A + T was 65.9%, which was significantly higher than that of G + C (34.1%), showing obvious AT bias, which was consistent with the bias of base composition of mitochondrial genes in most insects.

Table 1.
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The contents and nucleotide substitutions of COI gene sequences of Parachironomus.

T (%) C (%) A (%) G (%) ii si sv R
1st 48.3 8.2 40.0 3.5 144 30 44 0.7
2nd 25.3 18.5 27.6 28.6 205 11 1 13.3
3rd 42.9 27.0 13.6 16.5 216 0 0 3
Avg 38.8 17.9 27.1 16.2 565 41 44 0.9
TT TC TA TG CT CC CA CG
1st 76 11 18 1 10 5 2 0
2nd 49 5 0 0 5 35 0 0
3rd 93 0 0 0 0 58 0 0
Avg 218 16 18 2 14 98 2 0
AT AC AA AG GT GC GA GG
1st 18 2 62 5 1 0 4 2
2nd 0 0 59 1 0 0 1 61
3rd 0 0 29 0 0 0 0 36
Avg 18 2 151 6 2 0 4 98

The neighbor joining tree based on available COI DNA barcodes of the Parachironomus revealed two species new to science (Fig. 1). Parachironomus wangi Liu & Lin, sp. nov. is closer to Parachironomus biannulatus Staeger, 1839; and Parachironomus nankaiensis Liu & Lin, sp. nov. is closer to Parachironomus cayapo Spies, Fittkau & Reiss, 1994. The new species separate from the other sequenced species by more than 11% divergence in the COI barcode sequences (Table 2).

Table 2.
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Kimura 2-parameter pairwise genetic distances based on COI barcodes of the Parachironomus.

Species Pairwise genetic distances
P. tenuicaudatus|MG172661
P. varus|MZ606874 0.13
P. digitalis|MZ627020 0.14 0.13
P. frequens|MZ629002 0.15 0.15 0.13
P. parilis|MZ627840 0.13 0.09 0.14 0.14
P. gracilior|MZ624787 0.13 0.12 0.14 0.13 0.10
P. siljanensis|KC250820 0.14 0.10 0.13 0.15 0.11 0.11
P. cf. vitiosus|HQ937673 0.14 0.13 0.15 0.13 0.15 0.15 0.14
P. monochromus|MZ657902 0.15 0.14 0.14 0.14 0.14 0.15 0.15 0.13
P. vitiosus|MZ660486 0.12 0.14 0.14 0.13 0.13 0.15 0.14 0.07 0.13
P. subalpinus|JF870871 0.10 0.13 0.14 0.14 0.12 0.13 0.14 0.14 0.14 0.14
P. elodeae|KM571020 0.12 0.10 0.14 0.14 0.12 0.13 0.13 0.11 0.13 0.11 0.11
P. vitiosus group 0.14 0.13 0.15 0.13 0.14 0.15 0.14 0.00 0.13 0.08 0.13 0.11
P. potamogeti 0.13 0.12 0.14 0.14 0.14 0.15 0.14 0.15 0.12 0.13 0.12 0.12 0.15
P. swammerdami|LC329152 0.13 0.12 0.14 0.12 0.13 0.14 0.12 0.13 0.15 0.12 0.13 0.11 0.13 0.12
P. delinificus|KC750457 0.14 0.13 0.13 0.11 0.14 0.13 0.14 0.13 0.14 0.13 0.14 0.13 0.13 0.14 0.14
P. cayapo 0.15 0.13 0.16 0.14 0.14 0.15 0.14 0.15 0.14 0.14 0.15 0.13 0.15 0.15 0.14 0.14
P. paradigitalis|MZ660327 0.12 0.07 0.13 0.14 0.10 0.13 0.11 0.11 0.13 0.13 0.13 0.09 0.11 0.13 0.10 0.12 0.12
P. biannulatus|MZ658910 0.13 0.11 0.15 0.15 0.12 0.15 0.13 0.13 0.13 0.13 0.13 0.09 0.13 0.12 0.11 0.15 0.14 0.10
P. demissum comb. nov. |XL592 0.14 0.14 0.11 0.13 0.14 0.13 0.14 0.13 0.15 0.13 0.13 0.13 0.12 0.13 0.13 0.12 0.14 0.13 0.15
P. nankaiensis sp. nov. |XL599 0.14 0.13 0.12 0.13 0.13 0.12 0.14 0.14 0.15 0.14 0.12 0.13 0.14 0.15 0.14 0.13 0.13 0.12 0.15 0.13
P. demissum comb. nov. |XL590 0.14 0.14 0.11 0.13 0.14 0.13 0.13 0.12 0.14 0.12 0.12 0.13 0.12 0.13 0.13 0.12 0.13 0.12 0.15 0.01 0.12
P. wangi sp. nov. |XL601 0.14 0.14 0.14 0.15 0.14 0.15 0.16 0.14 0.15 0.14 0.14 0.14 0.14 0.15 0.12 0.14 0.16 0.14 0.15 0.12 0.14 0.12
P. wangi sp. nov. |XL602 0.14 0.14 0.14 0.15 0.14 0.15 0.16 0.14 0.15 0.14 0.14 0.14 0.14 0.15 0.12 0.14 0.16 0.14 0.15 0.12 0.14 0.12 0.00
Figure 1. 

Neighbor-joining tree for 20 species of the genus Parachironomus based on K2P distance in DNA barcodes. Numbers on branches represent bootstrap support (> 70%) based on 1000 replicates; scale equals K2P genetic distance.

When the interspecific genetic distance is greater than the intraspecific genetic distance, barcode gaps will appear through the frequency histogram of genetic data. There is an obvious barcode gap in the genetic distance of all Parachironomus COI sequences, which fully confirms the feasibility of COI as a DNA barcode (Fig. 2).

Figure 2. 

Histogram of pairwise K2P distances of 24 COI barcodes of Parachironomus.

Taxonomic descriptions

Parachironomus demissum Yan, Wang & Bu, 2012, comb. nov.

Figs 3, 4, 5

Paracladopelma demissum Yan, Wang & Bu, 2012: 291.

Material examined

Holotype. Male (TJNU: 11430), China, Sichuan Province, Yajiang County, Sandaoqiao Town, 30.01532°N, 101.05134°E, 2460 m a.s.l., 9.VI.1996, light trap, leg: X. H. Wang. Paratypes. One male (TJNU: 11730), China, Sichuan Province, Ya’an City, Baoxing County, Xinglong Elementary School, Xihe River, 30.25800°N, 102.50387°E, 1100 m a.s.l., 19.VI.1996, light trap, leg: X. H. Wang. One male (TJNU: 12886), China, Sichuan Province, Kangding County, Wasigou River, 30.04191°N, 102.09454°E, 2000 m a.s.l., 15.VI.1996, light trap, leg: X. H. Wang. One male (TJNU: 13079), China, Sichuan Province, Shimian County, Nanyahe River, 29.11156°N, 102.23265°E, 1040 m a.s.l., 16.VI.1996, light trap, leg: X. H. Wang.

Additional materials

Two males (SHOU: XL590, XL592), China, Xizang Autonomous Region, Rikaze City, Yadong County, Xiasima Town, 27.48986°N, 88.90572°E, 3032 m a.s.l., 20.VII.2014, light trap, leg: X. L. Lin.

Diagnostic characters

The species can be distinguished from known species of Parachironomus by the following combination of characters: AR 0.58–0.67, 0.62; tergite IX with shoulder-like posterior margin; anal point triangular base, constricted in the middle, with a ridge mesally; anal tergite bands V-shaped and fused; superior volsella with a bare triangular projection apically; gonostylus slender, parallel-sided, curved medially, gradually tapered to the top.

Description

Adult males (n = 6, unless otherwise stated). Total length 3.08–3.60, 3.35 mm. Wing length 1.60–1.89, 1.75 mm. Total length/wing length 1.81–2.10, 1.93. Wing length/length of profemur 2.16–2.63, 2.32.

Coloration. Thorax yellowish brown with pale brown spots. Femora and tibiae of front legs yellowish green with distal parts brown, anterior 1/2 of tarsi I yellowish green, remainder of front legs dark brown; femora, tibiae and basal 1/2 of tarsi I of mid and hind legs yellowish green, remaining dark brown. Abdomen yellowish green to dark brown, with tergites I–V yellowish green, tergites VII, VIII, and hypopygium dark brown.

Head (Fig. 3A). Antenna with 11 flagellomeres, ultimate flagellomere 250–290, 273 (3) μm long. AR 0.58–0.67, 0.62 (3). Frontal tubercles conical, 13–25, 18 (5) μm long, 8–20, 17 (5) μm wide at base. Temporal setae 17–20, 18; including 3–4, 3 inner verticals; 5–8, 8 outer verticals; and 6–9, 8 postorbitals. Clypeus with 12–16, 15 setae. Tentorium 105–132, 118 (5) μm long, 22–28, 24 (5) μm wide. Palpomere lengths (in μm):30–42, 37 (5); 35–45, 39 (5); 95–119, 109 (5); 130–148, 139 (5); 155–220, 190 (5); Pm5/ Pm3 1.48–2.05, 1.76 (5).

Figure 3. 

Head (A–C) and thorax (D–F) of Parachironomus species A P. demissum (Yan, Wang & Bu), comb. nov. B P. wangi Liu & Lin, sp. nov. C P. nankaiensis Liu & Lin, sp. nov. D P. demissum (Yan, Wang & Bu), comb. nov. E P. wangi Liu & Lin, sp. nov. F P. nankaiensis Liu & Lin, sp. nov. Scale bars: 200 μm.

Thorax (Fig. 3D). Antepronotals with 2–3, 2 setae, acrostichals 5–7, 6, dorsocentrals 7–8, 8, prealars 3. Scutellum with 12–14, 13 setae.

Wing (Fig. 5A). VR 1.18–1.34, 1.26. R with 13–18, 16 setae, R1 with 12–18, 15 setae, R4+5 with 12–22, 16 setae. Brachiolum with 2–3, 2 setae. Squama with 3–5, 4 setae.

Legs. Front tibia with 3 subapical setae, 80–84, 82; 83–97, 91 and 85–112, 101 (5) μm long. Combs of mid tibia 37–41, 39 μm wide with 18–25, 22 μm long spur, and 41–55, 48 μm wide with 20–34, 27 μm long spur; combs of hind tibia 37–41, 39 μm wide with 23–27, 25 μm long spur, 60–66, 63 μm wide with 28–34, 32 μm long spur. Tarsomere 1 of mid and hind legs without sensilla chaetica. Lengths (in μm) and proportions of legs as in Table 3.

Table 3.
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Lengths (in μm) and proportions of legs of Parachironomus demissum (Yan, Wang & Bu), comb. nov., adult male (n = 6).

fe ti ta1 ta2 ta3
P1 632–815, 755 498–640, 586 901–1049, 996 341–434, 407 276–352, 329
P2 575–810, 731 524–660, 600 317–370, 349 134–180, 169 99–133, 122
P3 730–910, 841 698–890, 802 496–549, 521 245–290, 275 187–246, 221
ta4 ta5 LR BV SV
P1 273–326, 305 152–170, 162 1.63–1.81, 1.69 1.94–1.95, 1.94 1.25–1.37, 1.34
P2 64–90, 84 66–70, 69 0.55–0.64, 0.58 3.75–3.90, 3.79 3.47–3.93, 3.81
P3 112–140, 126 80–96, 87 0.61–0.71, 0.65 3.01–3.07, 3.05 2.88–3.22, 3.15

Hypopygium (Figs 4A, D, 5B, C). Tergite IX with shoulder-like posterior margin, bearing 16–24, 20 setae at base of anal point. Laterosternite IX with 2 or 3, 3 setae. Anal point 55–67, 63 μm long, 12–25, 19 μm wide at base, 10–14, 13 μm wide apically, originating from caudal margin of anal tergite, triangular base, constricted in the middle, with a ridge mesally, moderately widen to distal and apically swollen (Fig. 4D). Anal tergite bands V-shaped and fused. Phallapodeme 52–70, 61 μm long. Transverse sternapodeme 30–52, 42 μm long. Superior volsella 55–65, 61 μm long, curved medially, expanded in the apical part, apically with a bare triangular projection, bearing two subapical setae, covered with microtrichia on inner margin. Inferior volsella with moderately blunt caudal projection, not reaching beyond anal tergite margin, and covered by microtrichia (Fig. 4G). Gonocoxite 90–131, 107 μm long, with three setae on inner margin. Gonostylus 140–174, 168 μm long, slender, parallel-sided, curved medially, gradually tapered to the top, bearing 12–24, 20 setae along inner margin and one stronger seta at apex. HR 0.55–0.94, 0.68. HV 1.86–2.50, 2.09.

Figure 4. 

Hypopygium A P. demissum (Yan, Wang & Bu), comb. nov. B P. wangi Liu & Lin, sp. nov. C P. nankaiensis Liu & Lin, sp. nov. Anal point D P. demissum (Yan, Wang & Bu), comb. nov. E P. wangi Liu & Lin, sp. nov. F P. nankaiensis Liu & Lin, sp. nov. Superior volsella G P. demissum (Yan, Wang & Bu), comb. Nov. H P. wangi Liu & Lin, sp. nov. I P. nankaiensis Liu & Lin, sp. nov. Scale bars: 50 μm.

Figure 5. 

Parachironomus demissum (Yan, Wang & Bu), comb. nov. holotype male A wing B hypopygium, dorsal view C hypopygium, ventral view.

Distribution

China (Sichuan and Xizang).

Parachironomus wangi Liu & Lin, sp. nov.

https://zoobank.org/DE07AF99-393F-407D-826E-FCA5C9B45FE1
Figs 3, 4, 6

Material examined

Holotype. Male (SHOU: XL601), China, Xizang Autonomous Region, Shannan City, Gongga County, Gangdui Town, 29.27888°N, 90.82323°E, 3586 m a.s.l., 18.VII.2014, sweep net, leg: X.L. Lin. Paratypes. One male (TJNU: XL602), collecting data as holotype.

Diagnostic characters

The species can be distinguished from known species of Parachironomus by the following combination of characters: frontal tubercles absent; tergite IX with triangular posterior margin; anal point slightly wider at base, parallel-sided, swollen apically; superior volsella wide, parallel-sided, bent inward at 1/3 distance from apex, apically rounded, free microtrichia; inferior volsella not reaching beyond anal tergite margin; gonostylus gradually widened distally, curved and parallel-sided, apically rounded.

Description

Adult males (n = 2, unless otherwise stated). Total length 3.63–3.91, 3.77 mm. Wing length 1.85–1.91, 1.88 mm. Total length/wing length 1.96–2.05, 2.01. Wing length/length of profemur 2.74–2.79, 2.77.

Coloration. Thorax yellowish brown with pale brown spots. Front legs dark brown; femora and basal 1/3 of tarsi I of mid and hind legs yellowish brown, remaining dark brown. Abdomen pale yellow to yellowish brown, with tergites I–VI pale yellow, tergites VII, VIII, and hypopygium yellowish brown.

Head (Fig. 3B). Antenna with 11 flagellomeres, ultimate flagellomere 502–536, 519 μm long. AR 1.54–1.55, 1.55. Frontal tubercles absent. Temporal setae 13–14, 14; including 2–4, 3 inner verticals; 4–6, 5 outer verticals; and 5 or 6, 6 postorbitals. Clypeus with 7–9, 8 setae. Tentorium 95–128, 112 μm long, 31–34, 33 μm wide. Palpomere lengths (in μm): 26–28, 27; 37–39, 38; 92–98, 95; 106–109, 108; 176–193, 185; Pm5/ Pm3 1.91–1.97, 1.94.

Thorax (Fig. 3E). Antepronotals with 1 or 2, 2 setae, acrostichals 4, dorsocentrals 8, prealars 3. Scutellum with 12 setae.

Wing (Fig. 6A). VR 1.10–1.16, 1.13. R with 5 or 6, 6 setae, R1 with 1 or 2, 2 setae, R4+5 with 2 setae. Brachiolum with two setae. Squama with 7–9, 8 setae.

Figure 6. 

Parachironomus wangi Liu & Lin, sp. nov. holotype male A wing B hypopygium, dorsal view C hypopygium, ventral view.

Legs. Front tibia with three subapical setae, 82–91, 87; 84 (1) and 105 (1) μm long. Combs of mid tibia 26–33, 30 μm wide with 15–25, 20 μm long spur, and 21 μm wide with 28 μm long spur; combs of hind tibia 22–26, 24 μm wide with 22–34, 28 μm long spur, 38–42, 40 μm wide with 34–38, 36 μm long spur. Tarsomere 1 of mid and hind legs without sensilla chaetica. Lengths (in μm) and proportions of legs as in Table 4.

Table 4.
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Lengths (in μm) and proportions of legs of Parachironomus wangi Liu & Lin, sp. nov., adult male (n = 2).

fe ti ta1 ta2 ta3
P1 664–695, 680 469–503, 486 858–940, 899 455–489, 472 337–355, 346
P2 692–700, 696 604–638, 621 348–362, 355 171–189, 180 126–135, 131
P3 726–751, 739 783–801, 792 560–594, 577 291–302, 297 220–231, 226
ta4 ta5 LR BV SV
P1 282–290, 286 147–152, 150 1.83–1.87, 1.85 1.62–1.67, 1.65 1.27–1.32, 1.30
P2 83–84, 84 75–78, 77 0.57–0.58, 0.57 3.50–3.61, 3.56 3.70–3.72, 3.71
P3 127–130, 129 90–93, 92 0.72–0.74, 0.73 2.82–2.86, 2.84 2.61–2.69, 2.65

Hypopygium (Figs 4B, E, H, 6B, C). Tergite IX with triangular posterior margin, bearing 4–8, 6 setae at base of anal point. Laterosternite IX with two setae. Anal point originating from caudal margin of anal tergite, slightly wider at base, parallel-sided, swollen apically, 56–60, 58 μm long, 17–21, 19 μm wide at base, 10 μm wide at apex (Fig. 4E). Anal tergite bands V-shaped, fused in the middle. Phallapodeme 79–81, 80 μm long. Transverse sternapodeme 39–45, 42 μm long. Superior volsella wide, parallel-sided, bent inward at 1/3 distance from apex, apically rounded, 50–61, 56 μm long, 12–14, 13 μm wide at apex, bearing an apical seta and a proximal lateral seta, both arising from distinct setal pits, free microtrichia. Inferior volsella with distinct blunt caudal projection, not reaching beyond anal tergite margin, and covered by microtrichia (Fig. 4H). Gonocoxite 119–135, 127 μm long, with 4 strong medial setae. Gonostylus 171–174, 173 μm long, narrower at base, gradually widened distally, curved and parallel-sided, apically rounded, bearing 6–8, 7 setae along inner margin and one stronger seta at apex. HR 0.70–0.78, 0.74. HV 2.12–2.25, 2.18.

Etymology

Name after Prof. Xin-Hua Wang, for his outstanding contribution towards increasing our knowledge of aquatic insect taxonomy; noun in nominative case.

Distribution

China (Xizang).

Parachironomus nankaiensis Liu & Lin, sp. nov.

https://zoobank.org/9524FD76-DA2D-4E37-90CD-EB6F4765A95D
Figs 3, 4, 7

Material examined

Holotype. Male (SHOU: XL599), China, Xizang Autonomous Region, Shannan City, Gongga County, Gangdui Town, 29.27888°N, 90.82323°E, 3586 m a.s.l., 18.VII.2014, sweep net, leg: X.L. Lin.

Diagnostic characters

The species can be distinguished from known species of Parachironomus by the following combination of characters: frontal tubercles small; squama with seven setae; anal tergite bands V-shaped, separated; superior volsella narrower at base, curved and expanded in the distal part, with a bare lamellar projection as wide as apex of volsella; inferior volsella reaching slightly beyond anal tergite margin; gonostylus slender, slightly curved in the middle, tapered to the apex.

Description

Adult male (n = 1). Total length 3.90 mm. Wing length 2.51 mm. Total length/wing length 1.56. Wing length/length of profemur 2.64.

Coloration. Thorax dark brown with dark spots. Legs brown. Abdomen yellowish green to brown, tergites I–V yellowish green, tergites VI–VIII yellowish brown, hypopygium brown.

Head (Fig. 3C). Antenna with 11 flagellomeres, ultimate flagellomere 699 μm long. AR 1.60. Frontal tubercles small, 9 μm long, 8 μm wide. Temporal setae 14, including 4 inner verticals; 4 outer verticals; and 6 postorbitals. Clypeus with 11 setae. Tentorium 154 μm long, 39 μm wide. Palpomere lengths (in μm): 30; 42; 115; 146; 235; Pm5/ Pm3 2.04.

Thorax (Fig. 3F). Antepronotals with 3 setae, acrostichals 6, dorsocentrals 10, prealars 3. Scutellum with 10 setae.

Wing (Fig. 7A). VR 1.11. R with 16 setae, R1 with 14 setae, R4+5 with 22 setae. Brachiolum with two setae. Squama with seven setae.

Figure 7. 

Parachironomus nankaiensis Liu & Lin, sp. nov. holotype male A wing B hypopygium, dorsal view C hypopygium, ventral view.

Legs. Front tibia with three subapical setae, 80, 87 and 93 μm long. Combs of mid tibia 33 μm wide with 19 μm long spur, and 29 μm wide with 27 μm long spur; combs of hind tibia 30 μm wide with 20 μm long spur, 65 μm wide with 36 μm long spur. Tarsomere 1 of mid and hind legs without sensilla chaetica. Lengths (in μm) and proportions of legs as in Table 5.

Table 5.
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Lengths (in μm) and proportions of legs of Parachironomus nankaiensis Liu & Lin, sp. nov., adult male (n = 1).

fe ti ta1 ta2 ta3
P1 950 744 1135 576 431
P2 889 825 448 258 187
P3 1056 1072 675 385 292
ta4 ta5 LR BV SV
P1 315 140 1.53 1.94 1.49
P2 120 91 0.54 3.30 3.83
P3 162 89 0.63 3.02 3.15

Hypopygium (Figs 4C, F, I, 7B, C). Tergite IX with 14 setae at base of anal point and shoulder-like posterior margin of anal tergite. Laterosternite IX with three setae. Anal point originating from caudal margin of anal tergite, almost parallel-sided, moderately expanded at apex, 50 μm long, 9 μm wide at base, 10 μm wide apically. Anal tergite bands V-shaped, separated (Fig. 4F). Phallapodeme 80 μm long. Transverse sternapodeme 59 μm long. Superior volsella narrower at base, curved and expanded in the distal part, with a bare lamellar projection as wide as apex of volsella, 80 μm long, 22 μm wide at apex; and bearing six long setae at apex, free microtrichia. Inferior volsella with fairly blunt caudal projection, reaching slightly beyond anal tergite margin, and covered with microtrichia (Fig. 4I). Gonocoxite 143 μm long, with four stout setae placed along inner margin. Gonostylus 169 μm long, slender, slightly curved in the middle, tapered to the apex, bearing seven setae along inner margin and one single seta at apex. HR 0.85. HV 2.31.

Etymology

Name after Nankai University, the institution of study and work for Prof. Xin-Hua Wang; noun in nominative case.

Distribution

China (Xizang).

Key to known adult males of Parachironomus from China

1 Tergite IX with shoulder-like caudal margin 2
– Tergite IX with triangle caudal margin 4
2 Superior volsella without projection; gonostylus with constriction in middle P. frequens (Johannsen)
– Superior volsella with a projection; gonostylus gradually tapered to the top 3
3 AR 0.58–0.67; anal tergite bands fused; inferior volsella not reaching beyond anal tergite margin P. demissum (Yan, Wang & Bu), comb. nov.
– AR 1.60; anal tergite bands separated; inferior volsella reaching slightly beyond anal tergite margin P. nankaiensis Liu & Lin, sp. nov.
4 Superior volsella short, bearing two apical setae and with folds on inner margin; gonostylus widened basally P. gracilior (Kieffer)
– Superior volsella elongate, bearing an apical seta and a subapical seta and without folds; gonostylus widened distally 5
5 Mid and hind tibiae each with 1 spur; superior volsella straightly, widened at base P. poyangensis Yan
– Mid and hind tibiae each with 2 spurs; superior volsella curved, widened in the distal part 6
6 Superior volsella slightly curved; gonostylus slender, with distinct expansion in distal 1/3 P. monochromus (van der Wulp)
– Superior volsella bent inward at1/3 distance from apex; gonostylus parallel-sided, gradually widened distally P. wangi Liu & Lin, sp. nov.

Discussion

In this study, the holotype of Paracladopelma demissum were examined, and the original description has been modified. The distinguishing feature of Parachironomus are that the superior volsella usually has a distinct preapical tooth as well as setae arising from distinct pits (Yan et al. 2012; pers. comm. Martin SpiesJuly. 2022). We re-checked the holotype, and the characters of tergite IX with shoulder-like posterior margin, superior volsella slender and with 2 distal setae arising from distinct pits, inferior volsella with blunt or pointed caudal projection conform to the characters of Parachironomus; therefore, Paracladopelma demissum should be placed in Parachironomus. Parachironomus demissum comb. nov. resembles Parachironomus digitalis Edwards, 1929 in having similarly shaped tergite IX, anal point and superior volsella, but the antenna ratio and some other measurements are different.

Parachironomus wangi Liu & Lin, sp. nov. resembles Parachironomus biannulatus Staeger, 1839 in having similar shapes of the superior volsella and posterior margin of tergite IX, but can be separated by the following combination characters: AR 1.54–1.55, anal point parallel-sided and gonostylus expanded apically in P. wangi Liu & Lin, sp. nov, whereas AR 3.0–3.6, the anal point is constricted in the middle, and the gonostylus is tapered to the apex in P. biannulatus.

Parachironomus nankaiensis Liu & Lin, sp. nov. resembles Parachironomus cayapo Spies, Fittkau & Reiss, 1994 in having similar shapes of anal point, inferior volsella, and anal tergite bands, but can be separated from the latter by the following combination characters: squama seven setae, the superior volsella expanded in the distal part and with a bare lamellar projection, plus with the gonostylus tapered to the apex. In contrast, the squama of P. cayapo is bare, the superior volsella is not widened in the distal part and has no projection, and the gonostylus has a protruding hump.

The results of molecular identification and morphological taxonomy are consistent, indicating that DNA barcodes and traditional morphological taxonomy are complementary in this case; therefore, the DNA barcode can be used as a simple method to supplement traditional morphological taxonomy for Parachironomus.

Biogeographically, the three species examined in this study are all distributed in the Tibetan Plateau at an altitude of more than 3,000 meters (Fig. 8). With the gradual increase of altitude, the climate gradually deteriorates, and Parachironomus living in high altitude areas have strong cold tolerance. The high biodiversity in Tibetan Plateau is demonstrated, as well as the distribution range of this genus extended.

Figure 8. 

Habitat for Parachironomus wangi, Liu & Lin, sp. nov.

In conclusion, this study not only enriches the database of Chironomidae in China, but also provides baseline data for the protection of the environment and biodiversity in the Tibetan Plateau.

Acknowledgements

We thank Dr. M. Spies (Zoologische Staatssammlung München, Germany) for providing input on various levels of this work. Financial support from National Natural Science Foundation of China is gratefully acknowledged (grant numbers: 32170473, 31801994, 31900344).

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