Taxonomic study on the genus Stenochironomus Kieffer from the Baishanzu Nature Reserve, China (Diptera, Chironomidae)
Author
Song, Chao
College of Life Sciences, Taizhou University, Taizhou, Zhejiang 318000, China
Author
Zhu, Bin-Qing
Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, Jiangsu, China
Author
Moubayed-Breil, Joel
https://orcid.org/0000-0002-6793-5746
Freshwater & Marine biology, 10 rue des Fenouils, F- 34070 Montpellier, France
Author
Lei, Teng
College of Life Sciences, Taizhou University, Taizhou, Zhejiang 318000, China
Author
Qi, Xin
College of Life Sciences, Taizhou University, Taizhou, Zhejiang 318000, China
qixin0612@163.com
text
ZooKeys
2022
2022-06-09
1104
93
113
http://dx.doi.org/10.3897/zookeys.1104.81403
journal article
http://dx.doi.org/10.3897/zookeys.1104.81403
1313-2970-1104-93
E19A929655A846408DC00F9E34357F1E
F277CDFEDF6E5A888F2AB68235745385
Stenochironomus okialbus Sasa, 1990
Figs 9
, 10
Stenochironomus okialbus
Sasa, 1990: 122, fig. 10.
Material examined.
3 male
adults,
collected by light trap
in
Zhejiang Province
,
Lishui City
,
Qingyuan County
,
Baishanzu National Nature Reserve
,
27.76°N
,
119.31°E
,
11-12.VIII.2020
, leg.
Song C.
Figure 9.
Male adult of
Stenochironomus okialbus
(in lateral view): new record to
China
Diagnostic characters.
Stenochironomus okialbus
differs from other related species by a combination of characters: wing with dark markings in the middle and apex; superior volsella short and small, spatulate, with four or five long setae; inferior volsella elongate, with 2-4 long setae and a slender terminal spine; posterior margin of tergite IX with 8-10 setae and eight spines.
Description.
Male imago (N = 3). Total length 2.94-3.98, 3.62 mm. Wing length 1.80-1.85 mm. Total length / wing length 1.85-2.20, Wing length / length of pro-femur 178-1.88.
Coloration
(Fig.
8
). Body almost pale yellowish or white, except postnotum with spot area and tergite IV-VII brown; wing with dark pigmentation on median and apical parts; all legs pale yellow with dark knees and apex of tibia.
Head.
AR 1.10-1.25, 1.12, ultimate flagellomere 430-660, 580
µm
long. Temporal with 12-16, 14 setae, including 7-8, 7 inner verticals, 4-7, 6 outer verticals and 1-2, 2 postorbitals. Clypeus with 12-20, 17 setae. Tentorium 155-220, 190
μm
long, 30-53, 44
μm
wide. Palpomere lengths (μm): 33-48, 37; 40-65, 55; 123-195, 170; 85-125, 116; 130-218, 194. Palpomere ratio (5th /3rd) 1.05-1.21, 1.13.
Thorax.
Dorsocentrals 14-21, 18; acrostichals 9-12, 11; prealars 5-6, 6; Scutellum with 7-12 setae in two rows.
Wings
.
VR 1.06-1.10, 1.08. Brachiolum with 1-2, 2 setae. Distribution of setae on veins: R, 20-29, 25; R1, 21-39, 31; R4+5, 49-53, 51. Squama with 10-18, 14 setae. Anal lobe normally developed.
Legs.
Fore leg: width at apex of tibia 53-63, 58
μm
, tibia with blunt scale 35-50, 44
µm
long. Mid leg: width at apex of tibia 53-70, 61
μm
, tibia with two apical spurs 43-53, 48 and 45-58, 52
µm
long. Hind leg: width at apex of tibia 58-73, 64
μm
, tibia with two apical spurs 45-55, 51 and 45-56, 52
µm
long. Lengths (in
μm
) and proportions of legs as in Table
6
.
Table 6.
Male adult of
Stenochironomus okialbus
. Lengths (in
µm
) and proportions of legs (
N
= 3, except where otherwise stated).
| - |
P1 |
P2 |
P3 |
| Fe |
920-1310, 1150 |
790-1220, 1053 |
930-1350, 1183 |
| Ti |
930-1210, 1050 |
730-1030, 913 |
870-1230, 1083 |
| Ta 1 |
1200-1640 (
N
= 2)
|
530-730, 653 |
710-990, 880 |
| Ta 2 |
590-810 (
N
= 2)
|
290-410, 360 |
380-520, 470 |
| Ta 3 |
500-680 (
N
= 2)
|
230-310, 277 |
290-410, 363 |
| Ta 4 |
450-650 (
N
= 2)
|
140-210, 180 |
180-250, 230 |
| Ta 5 |
210-300 (
N
= 2)
|
60-100, 87 |
80-110, 97 |
| LR |
1.45-1.48 (
N
= 2)
|
0.70-0.73, 0.72 |
0.80-0.82, 0.81 |
| BV |
1.63-1.69 (
N
= 2)
|
2.84-2.94, 2.90 |
2.69-2.75, 2.71 |
| SV |
1.42-1.46 (
N
= 2)
|
2.88-3.08, 3.00 |
2.53-2.61, 2.57 |
Hypopygium
(Fig.
10
). Anal point 110-125, 118
μm
long, 43-60; wide, 52
µm
width at base, 18-20, 18
µm
at apex; slightly swollen and rounded apically. Tergite IX with 19-25, 22 long setae on median part; posterior margin of tergite IX with 6 strong setae and 3 spines. Laterosternite IX with 3-4, 4 setae. Transverse sternapodeme 35-48, 41
μm
long; phallapodeme 85-95, 89
μm
long. Gonocoxite 138-175, 159
μm
long. Gonostylus 185-200, 196
μm
long. Superior volsella short, 25-30, 28
μm
long, 23-25, 24
μm
wide, with 4-5 long setae. Inferior volsella linearly elongate, 183-220, 208
μm
long, with 2-3 long setae and 1 stout terminal spine. HR 0.74-0.86, 0.81; HV 1.58-1.97, 1.84.
Figure 10.
Male adult of
Stenochironomus okialbus
.
A
hypopygium in dorsal view
B
hypopygium in ventral view
C
superior volsella.
Remarks.
The morphological characters of the Chinese specimens fit well with the original description and illustrations provided by
Sasa (1990)
: wing with two spotted areas; narrow dark rings on knee points; anal point slightly swollen and rounded. However, some relevant differentiating characters were observed within the examined specimens: the inferior volsella have only two or three long setae, while it bears four in the Japanese specimens; average values of the AR 1.10-1.25 are lower than 1.37-1.41 in the Japanese species.
According to the molecular data, specimen (LC462365) of
Stenochironomus okialbus
, shows a large genetic distance to other specimens (up to 14%); as the specimen is not accessible it should be rechecked. The K2P distance between Japanese and Chinese specimens is 1.7%, which well supports them as the same species.
Distribution.
Oriental China (Zhejiang) and Japan.