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Research Article
Two new species of Stenochironomus Kieffer (Diptera, Chironomidae) from Zhejiang, China
expand article infoXin Qi, Xiaolong Lin§, Yuedan Liu|, Xinhua Wang
‡ Taizhou University, Taizhou, China
§ Nankai University, Collefe of life sciences, Tian Jin, China
| The Key Laboratory of Water and Air Pollution Control of Guangdong Province, South China Institute of Environmental Sciences, the Ministry of Environm, guangzhou, China
¶ Nankai University, Tianjin, China
Open Access

Abstract

Two new species of Stenochironomus Kieffer (Diptera: Chironomidae: Chironominae), S. brevissimus sp. n. and S. linanensis sp. n., are described from China and the male imagines are illustrated. S. brevissimus sp. n. can be separated from the so far known species by having very short and small, spatulate superior volsella with two long setae, whereas S. linanensis sp. n. is easily separated from the other species of Stenochironomus by the following characters: wings transparent, body yellow, superior volsella finger-like, with nine long setae, elongated inferior volsella with four long setae and one well developed terminal spine; tergite IX with 10−15 long setae medially. A key to the males of Stenochironomus occurring in China is given.

Keywords

Stenochironomus , new species, key, China

Introduction

Stenochironomus Kieffer, 1919 is a species-rich genus with worldwide distribution, occurring in all biogeographical regions except in Antarctica (Cranston et al. 1989). The genus was erected by Townes in 1945 based on Chironomus pulchripennis (Coquillett, 1902) (Spies and Sæther 2004). The larvae are easily found mining decayed leaves or wood in freshwater habitats ranging from small ponds and swamps to fast-flowing streams and rivers (Cranston et al. 1989). Based on the different hosts of larvae and pupae, Borkent (1984) erected two subgenera: Stenochironomuss. str. Kieffer (larvae and pupae mine dead submerged wood) and Petalopholeus Borkent (larvae and pupae mine dead submerged leaves). This subdivision has not been adopted by subsequent authors, because immature stages are known only for a few species, which makes difficult to ascribe them to any subgenus (Pinho et al. 2005, Andersen et al. 2008, Qi et al. 2008, Dantas et al. 2010, Zorina 2010). To date, there are 97 species recorded around the word: 24 species from the Palaearctic Region, 17 from the Nearctic Region, 30 from the Neotropical Region, 16 from the Oriental Region, 16 from the Afrotropical Region and 4 from the Australasian Region (Qi et al. 2011, Reis et al. 2013).

Zhejiang Province is located in the Chinese central subtropical region, which has a humid monsoon climate. In Zhejiang, three species of Stenochironomus [S. koreanus Borkent, 1984, S. nubilipennis Yamamoto, 1981 and S. satorui (Tokunaga & Kuroda, 1936)] have been recorded (Wang 2000, Qi et al. 2011). In this paper, two new species of Stenochironomus from Zhejiang, Oriental China, are described and illustrated. A key to the males of Stenochironomus from China is presented.

Materials and methods

The morphological nomenclature follows Sæther (1980). Measurement methods follow Qi et al. (2012). The material examined was slide-mounted, following the procedure outlined by Sæther (1969). Specimens have been deposited in the College of Life Science, Taizhou University, China.

Abbreviations of parts measured are as follows:

AR Antennal ration, length of 13th / length of flagellomeres 1–12

Palpomere ratio (5th/3rd) Length of the 5th Palpomere / length of the 3rd Palpomere

VR Venarum ration, length of Cubitus (Cu) / length of Media (M)

BV Length of (femur + tibia + ta1) / length of (ta2 + ta3 + ta4 + ta5)

LR Leg ration, length of ta1 / length of tibia

SV Length of (femur + tibia) / length of ta1

HR Hypopygium ration, length of gonocoxite / length of gonostylus

HV Hypopygium value, total length / length of gonostylus times ten

p1 Fore leg

p2 Mid leg

p3 Hind leg

fe femur

ti tibia

ta1…tan tarsus1…tarsusn

R Radius

R1 Radius 1 vein

R4+5 Radius 4+5 vein

Taxonomy

Stenochironomus brevissimus sp. n.

Figs 1–10

Diagnosis

The adult male of S. brevissimus sp. n. can be distinguished from all other species of Stenochironomus by the following combination of characters: superior volsella very short and small, spatulate, with 2 long setae, elongated inferior volsella with 6 long setae, posterior margin of tergite IX with 20−22 setae and 8 spines.

Description

Male imago (n = 3). Total length 4.3−4.6 mm. Wing length 2.2−2.5 mm. Total length / wing length 1.8−1.9. Wing length / length of profemur 1.7−1.8.

Coloration. Head yellow, antenna brown. Thorax light yellow, postnotum and scutum with brown spots. Wings transparent, without any pigmentation. Abdomen and hypopygium yellow, anal point brown. Fore legs yellow with femur apically brown. Mid legs with apex and posterior basal region of femur with dark brown stripes, tibia brown, tarsomeres 1–5 yellow. Hind legs brown with femur yellow with dark brown stripes at apex.

Head (Fig. 1). AR 1.80−1.92. Temporal with 10−12 setae. Clypeus with 20−22 setae. Tentorium 173−176 mm long, 43−46 mm wide. Stipes 140−145 µm long, 10−13 µm wide. Palpomere lengths (in mm): 60−63, 60−65, 210−230, 140−150, 260−300. Palpomere ratio (5th/3rd) 1.2−1.3.

Figures 1–10. 

Stenochironomus brevissimus sp. n., male. 1 head 2 wing 3 thorax, lateral view 4 legs coloration (a. fore leg; b. mid leg; c. hind leg) 5 fore tibial apex, ventral view 6 mid tibial apex, lateral view 7 hind tibial apex, lateral view 8 hypopygium 9 spines on posterior margin of tergite IX, ventral view 10 superior volsella.

Wings (Fig. 2). VR 1.08−1.15. Brachiolum with 3−4 setae; R with 25−32 setae, R1 with 27−30 setae, R4+5 with 41−42 setae. Squama with 8−10 setae.

Thorax (Fig. 3). Dorsocentrals 12−14, acrostichals 14−16, prealars 4−5. Scutellum with 6−7 setae.

Legs (Fig. 4). Fore leg: width at apex of tibia 60−65 mm, tibia with scale 53−56 µm long, with 2−4 strong setae (Fig. 5). Mid leg: width at apex of tibia 80−83 mm, tibia with two apical spurs 40−50, 43–53 μm long. Hind leg: width at apex of tibia 70−80 mm, tibia with two apical spurs 40−50, 40–55 μm long. Mid and hind tibiae with fused combs (Figs 6–7), each comb 36−50 µm long. Lengths (in mm) and proportions of legs in Table 1.

Table 1.

Lengths (in µm) and proportions of leg segments in Stenochironomus brevissimus sp. n. (n = 3).

p1 p2 p3
Fe 1300−1400 1125−1200 1325−1525
Ti 1300−1500 1000−1125 1275−1400
ta1 1500−1600 725−800 950−1100
ta2 775−875 375−450 525−625
ta3 675−750 340−410 440−500
ta4 525−600 200−290 260−360
ta5 250−300 90−110 110−130
LR 1.07−1.15 0.71−0.73 0.74−0.79
BV 1.78−1.84 2.48−2.83 2.49−2.66
SV 1.73−1.81 2.91−2.95 2.66−2.74

Hypopygium (Fig. 8). Anal point 113−120 mm long, 15−20 µm wide at base, 13−15 µm wide at apex, parallel-sided, slender, apically rounded. Tergite IX with 16−17 long setae medially, posterior margin of tergite IX with 20−22 setae and 8 spines (Fig. 9). Phallapodeme 120−123 mm long; transverse sternapodeme 30−50 mm long. Gonocoxite 200−230 mm long. Superior volsella short, small and spatulate, 16−18 mm long, 20−22 mm wide, with 2 long setae (Fig. 10). Inferior volsella elongated, 190−200 mm long, with 6 long setae. Gonostylus 210−230 mm long, with 4 long setae along inner margin in distal 1/3. HR 0.95−1.00, HV 1.89−2.04.

Female, pupa and larva

Unknown.

Type material

Holotype: Male, CHINA, Zhejiang, Quzhou City, Hunan County, 19.iv.2012, leg. XL Lin, sweep net. 2 Paratypes: 2 males, same data as holotype.

Etymology

The specific epithet is a Latin adjective “brevissimus”, meaning the shortest, and refers to the superior volsella, which is the shortest in the genus.

Remarks

S. brevissimus sp. n. is similar to S. hainanus Qi, Shi & Wang, 2008 and S. okialbus Sasa, 1990 in having short and small superior volsella, but can separated from these species by the differences given in Table 2.

Table 2.

Main differences between S. brevissimus sp. n., S. hainanus and S. okialbus.

S. brevissimus S. hainanus S. okialbus
Wing transparent, without any pigmentation transparent, without any pigmentation with dark bands across the middle and posterior area
Coloration thorax light yellow, postnotum and scutum with brown spots; fore legs yellow with femur apically brown; mid legs with apex and posterior basal region of femur with dark brown stripes, tibia brown, tarsomeres 1–5 yellow; hind legs brown with femur yellow with dark brown stripes at apex whole body yellow, without dark pigmentation thorax yellow; fore legs yellow with femur apically brown, apex and basal region of tibia with dark brown stripes; mid legs yellow with femur apically brown; hind legs yellow with femur apically brown
Superior volsella with 2 setae with 3 setae with 4 setae
Inferior volsella with 6 setae with 3 setae with 4 setae and a strong terminal spine
Posterior margin of tergite IX with 20−22 setae and 8 spines with 16 setae with 8 setae and 8 spines

Distribution

The species is currently known only from Zhejiang Province of Oriental China.

Stenochironomus linanensis sp. n.

Figs 11–18

Diagnosis

The adult male of S. linanensis sp. n. can be distinguished from all other species of Stenochironomus by the following combination of characters: wings transparent, body yellow, superior volsella finger-like, with 9 long setae, elongated inferior volsella with 4 long setae and one well-developed terminal spine, tergite IX with 10−15 long setae medially.

Description

Male imago (n = 5). Total length 2.9−3.8 mm. Wing length 1.4−1.5 mm. Total length / wing length 1.98−2.41. Wing length / length of profemur 1.30−1.57.

Coloration. Head yellow. Thorax greenish yellow. Wings transparent, without any pigmentation. Abdomen yellow, hypopygium brown. Legs pale yellow.

Head (Fig. 11). AR 1.20−1.32. Temporal with 8−14 setae. Clypeus with 9−10 setae. Tentorium 153−156 mm long, 37−42 mm wide. Stipes 72−95 µm long, 5−6 µm wide. Palpomere lengths (in mm): 45−47, 28−33, 53−60, 75−90, 110−120. Palpomere ratio (5th/3rd) 2.00−2.07.

Figures 11–18. 

Stenochironomus linanensis sp. n., male. 11 head 12 wing 13 thorax, lateral view 14 fore tibial apex, ventral view 15 mid tibial apex, lateral view 16 hind tibial apex, lateral view 17 hypopygium 18 superior volsella.

Wings (Fig. 12). VR 1.07−1.20. Brachiolum with 2 setae; R with 16−23 setae, R1 with 17−18 setae, R4+5 with 22−28 setae. Squama with 5−7 setae.

Thorax (Fig. 13). Dorsocentrals 9−13, acrostichals 9−14, prealars 4−5. Scutellum with 5−6 setae.

Legs. Fore leg: width at apex of tibia 33−47 mm, tibia with scale 33−46 µm long, with 2−3 strong setae (Fig. 14). Mid leg: width at apex of tibia 50−65 mm, tibia with two apical spurs 25−28, 30–40 μm long. Hind leg: width at apex of tibia 50−60 mm, tibia with two apical spurs 32−39, 35–40 μm long. Mid and hind tibiae with fused combs (Fig. 15–16), each comb 18−22 mm long. Lengths (in mm) and proportions of legs in Table 3.

Table 3.

Lengths (in µm) and proportions of leg segments in Stenochironomus linanensis sp. n.

p1 p2 p3
fe 925−1075 625−700 650−725
ti 700−875 650−725 750−900
ta1 925−1100 475−550 780−950
ta2 500−725 200−260 400−600
ta3 400−500 210−300 300−350
ta4 320−400 130−200 240−300
ta5 140−200 70−80 100−120
LR 1.25−1.32 0.73−0.75 1.04−1.06
BV 1.67−1.88 2.35−2.87 1.88−2.10
SV 1.76−1.83 2.60−2.68 1.71−1.79

Hypopygium (Fig. 17). Anal point 65−73 mm long, 14−20 µm wide at base, 6−8 µm wide at apex, apex of anal point slightly swollen and rounded. Tergite IX with 10−15 long setae medially, posterior margin of tergite IX with 12−14 setae and 4 spines. Phallapodeme 70−80 mm long; transverse sternapodeme 35−38 mm long. Gonocoxite 160−180 mm long. Superior volsella finger-like, 53−63 mm long, 25−27 mm wide, with 9 long setae (Fig. 18). Inferior volsella elongated, 160−170 mm long, with 4 long setae and one well-developed terminal spine. Gonostylus 123−170 mm long, with 9 long setae along inner margin in distal 1/2. HR 0.94−1.47, HV 1.98−2.35.

Female, pupa and larva

Unknown.

Type material

Holotype: Male, CHINA, Zhejiang, Linan City, Qingliangfeng Mountain, 16.v.2012, leg. XL Lin, sweep net. 4 Paratypes: 4 males, same data as holotype.

Etymology

The specific epithet is an adjective referring to the type locality, Linan City.

Remarks

S. linanensis sp. n. is similar to S. macateei (Malloch, 1905), S. maculatus Borkent, 1984 and S. recticaudatus Borkent, 1984 in the structure of the hypopygium and the inferior volsella with a strong terminal spine, but can be separated from these species by the differences given in Table 4.

Table 4.

Main differences between S. linanese sp. n., S. macateei, S. maculatus and S. recticaudatus.

S. linanese S. macateei S. maculatus S. recticaudatus
Wing transparent transparent entire wing with pigmentation transparent
Median setae of tergite IX 10−15 35−37 25−28 35−37
posterior margin of tergite IX with 12−14 setae and 4 spines with 8 setae and 6 spines with 8 setae and 4 spines with 14 setae and 8 spines
Anal point apex of anal point slightly swollen and rounded parallel-sided apex of anal point slightly swollen and rounded apex of anal point slightly swollen and rounded
Superior volsella with 9 setae with 4−5 setae with 4−6 setae with 6 setae
Coloration whole body yellow, without dark pigmentation whole body yellow, without dark pigmentation postnotum, scutum and scutellum with dark pigmentation; other parts of body yellow dark pigmentation entirely absent except on tarsomeres 3−5 of all legs

Distribution

The species is known from Zhejiang Province of Oriental China.

Key to males of the genus Stenochironomus in China

1 Inferior volsella with a well-developed terminal spine 2
Inferior volsella without a well-developed terminal spine 7
2 Wing membranes with dark pigmentation 3
Wing membranes without any pigmentation 4
3 Legs almost entire brown, posterior area smoky area between veins C and M pale S. gibbus (Fabricius, 1805)
Legs yellow; entire wing smoky gray S. maculatus Borkent, 1984
4 Apex of anal point swollen and rounded 5
Apex of anal point not swollen and rounded 6
5 Superior volsella with 9 setae; posterior margin of tergite IX with 12−14 setae and 4 spines S. linanensis sp. n.
Superior volsella with 4 setae; posterior margin of tergite IX with 14−16 setae S. koreanus Borkent, 1984
6 Posterior edge of tergite IX with 8 long setae and 6 spines; anal point parallel-sided S. macateei (Malloch, 1915)
Posterior edge of tergite IX with 14 long setae, without any spine; anal point roughly triangular, apically pointed S. mucronatus Qi, Shi & Wang, 2008
7 Wing membranes with dark pigmentation 8
Wings without any pigmentation or with narrow pigment areas around RM and along veins M3+4 and Cu1 10
8 Abdomen and hypopygium light yellow S. inalemeus Sasa, 2001
Abdominal tergites I−IV light yellow, tergites V−VIII light brown, hypopygium dark brown 9
9 Preepisternum with brown spots; anal point slender and parallel-sided, apically rounded S. nubilipennis Yamamoto, 1981
Preepisternum without any pigmentation; anal point slender and parallel-sided, apically pointed S. satorui (Tokunaga & Kuroda, 1936)
10 Posterior margin of tergite IX with spines S. brevissimus sp. n.
Posterior margin of tergite IX without spines 11
11 Entire body yellow, without dark pigmentation; wings transparent, without any pigmentation; inferior volsella with 3 long setae S. hainanus Qi, Shi & Wang, 2008
Body yellow, with brown spots on thorax, abdomen, hypopygium and legs; wings with narrow pigment areas around RM and along veins M3+4 and Cu1; inferior volsella with 6 long setae S. totifuscus Sublette, 1960

Acknowledgements

Financial support from the National Natural Science Foundation of China (NSFC, grant No. 31301908, 31272284) and the Zhejiang Provincial Natural Science Foundation of China (grant No. Y3100486) are acknowledged with thanks.

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