Chironomus "orientalis"

This species is related to C. flaviplumus in Japan, but a new name was needed for this species (Martin 2011b). Description as C. orientalis is in process.

This type was identified as C. flaviplumus from the Yangtze River basin in China by Chen and Zhang (GenBank 2015 - unpubl.), for which only the DNA BARCODE sequence is available.  Limited information on the larva was available from Thailand (Pramual et al. 2016).
This description is based on Australian material.

In Bold bin: BOLD:AAV5954.

Adults:


Adult from Queensland (photo by Graeme V. Cocks)

Males

See here for proposed Holotype male.


C. "orientalis" male hypopygium (left) and superior volsella (right) (note beaked shape)

AR about 2.4-2.9.
Frontal tubercles about 33-39 µm, and about 3 times longer than wide.
Palp proportions (micron): 44 : 53 : 189 : 222 : 315
Wing length: 2.45-3.15 mm; wing width 0.30-0.67 mm.  VR about 1.02-1.07; abt 2-4 SCf on brachiolum; 9-14 setae in squamal fringe.
Thoracic setae - achrostichal about 12-18; dorsocentral about 13-18; prealar about 4-6; supra alar 1; scutellar in 2 approximate rows, 6-7 in anterior row, 11-17 in posterior row.
Leg pale; lengths (micron) and proportions as follows:


Male
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
BR
PI
1350
975
1820
925
837
712
362
1.82-1.96
1.35-1.44
1.7-2.2
PII
1305
1155
750
395
268
168
125
0.62-0.67
1.11-1.17
-
PIII
1478
1385
1180
595
448
262
152
0.81-0.92
1.05-1.09
-

Abdomen pale (greenish) with a relatively broad brown band about the middle of segments II-V, then covering most of the following segments.
The superior volsella is essentially a D(e)-type of Strenzke (1959), although often of a beaked type not illustrated by Strenzke (1959), i.e. it varies between a D- and an almost S-type.
Setae on 9th tergite: 9-12; some setae on inferior volsella with a simple or trifid fork; gonostylus reduces fairly sharply over posterior half.

Female:
Wing length 3.28-3.53 mm; width at cross vein 0.83-0.90 mm, VR 1.08-1.21.$nbsp;$nbsp;About 2-4 SCf on brachiolum; 17-22 setae in squamal fringe.
Head with frontal tubercles about 14 µm long and 13 µm wide; about 27-55 clypeal setae.
Antennal segments (microns): 190 : 127 : 147 : 121 : 215.$nbsp;$nbsp;AR about 0.36; A5/A1 about 1.13.
Thoracic setae - acrostichal about 13-17; dorsolateral about 32-44; prealar about 5; supra alar 1; scutellar in two approximate rows, 5 in anterior row; 11 in posterior row.
Leg proportions (micron)


Female
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
Ta4/Ti
PI
1640
1180
2290
1347
1102
1112
410
1.91-1.92
1.37-1.42
0.90-0.97
PII
1565
1400
828
438
309
192
143
0.58-0.61
1.11-1.14
-
PIII
1703
1640
1322
695
544
311
185
0.79-0.82
1.02-1.06
-
ant Ta4/Ti about 0.98; Ta3 and Ta4 subequal in length.

Abdomen pale, probably greenish; about 4 setae on gonopophysis VIII.

Differences from other members of the C. samoensis/flaviplumus group:
Important features of males are the AR of 2.4-2.9 (lower than that of C. flaviplumus, but similar to C. samoensis), LR of about 1.8-2.0 and fore Ta5, which is about 0.35-0.4 length of Ti.
In the female the fore legs are very long, with LR about 1.9, and Ta3 and Ta4 are about equal in length, only a little shorter than Ta2, ratio Ta4/Ti about 0.98
See here for descriptions of C. samoensis Edwards.

Pupa: Exuvia length about 7.4 (7.2-7.8) mm; inner margin of wing case 1.45-1.54 mm.  Cephalic tubercles (see below) variable, length from 23-38 µm, with subterminal setae about 56-61 µm long.  Basal ring of respiratory horn kidney shaped, about 124-137 µm long and 56-68 µm wide, HR 2.0-2.2.
Small Pedes spurii B and about 68-72 recurved hooks on abdominal segment II; well developed Pedes spurii A on segment IV, about 34 µm long and 24 µm wide (l/w 1.4).  Caudolateral spur (see below) of segment VIII with 1.8 (1, 2 or sometimes 3) spines, the additional spines reduced in size.  Anal fringe with about 65 (44-86) taeniae in multiple rows.


C. "orientalis": Cephalic tubercles (above) and caudolateral spur of segment VIII (below)

Fourth instar larva: a medium sized plumosus-type larva (length about 11.8 (9-14.3 (female), 10.9 (10.7-11)(male) mm., lab. reared).  Anterior ventral tubules 1.49 (1.24-1.84 mm.), shorter than posterior pair 1.72 (1.40-2.48) mm.
Gula pale or very slightly darkened on posterior third;  frontoclypeus pale to dark.  Clypeal aperture about 3.64 (2.60-4.43) times longer than wide.
Mentum (Fig. b) with square sharp teeth, c2 teeth of central trifid tooth well separated from c1 tooth (type III), 4th laterals slightly to moderately reduced (type I-II); about 0.53-0.59 times the ventral head length.
Ventromentum (Fig. c) about 183 (180-185) µm long and 3.87 (3.72-4.05) times longer than deep, with about 34.2 (31-38) striae; VMR about 0.29 (0.25-0.32); about 1.17 (1.13-1.22) times the mentum width.
Pecten epipharyngis (Fig. a) with about 16-21 variable but sharp teeth which become smaller at the ends.  Premandible (Fig. b) with teeth about equal, or perhaps outer tooth slightly longer, inner tooth about 2-2.4 times wider than the outer.
Distance between the antennal bases slightly larger than the distance between the S4 setae, which are separated by about 0.82-0.87 of the width of the mentum at that point.
Antenna (Fig. d) with a moderately long basal segment, which is about 3.74 (3.62-4.03) times as long as wide; AR about 1.87 (1.62-2.05).  Antennal proportions: 116 : 34: 9 : 12 : 8.
Distance between the antennal bases slightly larger than the distance between the S4 setae, which are separated by about 0.82-0.87 of the width of the mentum at that point.
Mandible (Fig. e) with third inner tooth only slightly darkened (Type IA/B), and with about 13.1 (12-14) grooves on outer surface near the base; MTR about 0.35 (0.32-0.38); 11.8 (10-13) taeniae in Pecten mandibularis.

Cytology:  4 polytene chromosomes with the pseudothummi arm combination AE, BF, CD, G.
Nucleolus virtually terminal in arm G; well developed BR about one third from the other end, and a smaller BR close to this other end; closely paired.  No nucleolus in long chromosomes.
Arm A differs from that of C. flaviplumus by a complex inversion, and arm F by possibly a simple inversion.  Irradiation experiments indicated only that the MD region was not on the CD chromosome.
"orl"A1:    1 - 2c, 10 - 12, 3 - 2d, 9 - 4, 13 - 19                                                  as holomelas
"orl"B1:    Puff of group 7 just distal to the middle of the arm with dark bands distal of it.
"orl"C1:    Characteristic groups 3-4 about one third from distal end of the arm.
"orl"D1:
"orl"E1:    1 - 3e, 10b - 3f, 10c - 13                                                                     as aprilinus, etc.
"orl"F1:    (possibly) 1 - 2a, 10a-d, 15 - 14e, 9 - 2b, 11 - 14d, 16 - 23               In14d-9 from flaviplumus
"orl"G1:    Subterminal nucleolus, median and distal BRs.

Molecular Sequence:
CO1 - GenBank accession nos. for Chinese specimens are KP902730-31 and for Thailand KT213029-038.  In BOLD they have 99.5% similarity to an early release sequence named as ChironomidaeGC sp. 7 from Queensland, Australia.

Found: China - Yangtze River basin (30.09°N, 115.12°E) (GeneBank, as C. flaviplumus)
            Bangladesh - Chittagong (22.4685°N, 91.7808°E)(BOLD)
            Malaysia - Botanical Gardens, Univ. Malaya, Selangor (3.1295°N, 101.656°E)(BOLD)
            Thailand - Mahasarakham University (16.242°N, 103.260°E), and Ban Keab (16.250°N, 103.210°E), Kantharawichai Dist.,
            Maha Sarakham; Ban Tha Reu (15.303°N, 103.392°E), Satuek Dist. Buri Ram.
            Widespread in the Orient.
            Also in Australia - Northern Territory & Queensland.

Indian specimens described by Chattopadhyuy et al. (1991) are not the same species and one has been renamed C. indiaensis (Martin 2011b), while others are the widespread species PK2.

This species can be bred in the laboratory, as fertile egg masses were obtained from adults reared from wild collected larvae in Australia. The related Japanese species has also been maintained in a laboratory culture (Elbetieha and Kalthoff 1988).

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Modified: 21 June 2020
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Copyright © 2005-2020, Jon Martin.