Oriental Chironomus: C. "orientalis"

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:

C. flaviplumus type 3: Male hypopygium (left) and superior volsella (right) (note beaked shape)

Males

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: 2.85 - 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:

	Fe	Ti	Ta1	Ta2	Ta3
PI	1350	975	1820	925	837
PII	1305	1155	750	393	268
PIII	1478	1385	1180	595	448
	Ta4	Ta5	LR	F/T	BR
PI	712	362	1.82-1.96	1.35-1.44	1.7-2.2
PII	168	125	0.62-0.67	1.11-1.17
PIII	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 volsellae with a simple or trifid fork; gonostylus reduces fairly quickly 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)

	Fe	Ti	Ta1	Ta2	Ta3
PI	1664	1196	2290	1255	1189
PII	1588	1410	845	452	313
PIII	1727	1663	1338	706	557
	Ta4	Ta5	LR	F/T	BR
PI	1189	405	1.91-1.92	1.37-1.42	1.44-1.82
PII	196	152	0.58-0.61	1.11-1.14	-
PIII	317	190	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: Exuviae length about 7.2-7.8 mm; inner margin of wing case 1.42-1,45 mm. Cephalic tubercles (see below) variable, length from 23-121 µm, with subterminal setae about 60 µm long.
About 51-68 recurved hooks on abdominal segment II. Caudolateral spur (see below) of segment VIII with 1, 2 or sometimes 3 spines. Anal fringe with about 74-100 taeniae in multiple rows.

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

Larva: a medium sized plumosus-type larva (length about 10.7-14.3 mm, lab. reared). Anterior ventral tubercles (1.24-1.84 mm) shorter than posterior pair (1.40 - 2.28 mm).
Gula pale or very slightly darkened on posterior third; frontoclypeus pale to dark.
Mentum (Fig. b) with square sharp teeth, c2 teeth of central trifid tooth well separated from c1 tooth (type III), 4th laterals only slightly reduced (type I).
Ventromental plates (Fig. c) separated by about a third of the width of the mentum, with about 29 - 34 striae; VMR about 0.29-0.35. Pecten epipharyngis (Fig. a) with about 16-21 sharp teeth which become much smaller at the ends.
Antenna (Fig. d) with a moderately long basal segment, which is about 4-4.5 times as long as wide; AR about 1.70-1.96. Antennal proportions (micron): 122 : 31 : 10 : 13 : 6.Distance between the antennal bases about equal to the distance between the S4 setae.
Mandible (Fig. e) with third inner tooth only partly separated and slightly darkened (Type IA/B); with about 12-14 grooves on outer surface near the base.

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.
"fl3"A1: 1 - 2c, 10 - 12, 3 - 2d, 9 - 4, 13 - 19 as holomelas
"fl3"B1: Puff of group 7 above the middle of the arm with dark bands distal of it.
"fl3"C1: Characteristic groups 3-4 about one third from distal end of the arm.
"fl3"D1:
"fl3"E1: 1 - 3e, 10b - 3f, 10c - 13 as aprilinus, etc.
"fl3"F1: (possibly) 1 - 2a, 10a-d, 15 - 14e, 9 - 2b, 11 - 14d, 16 - 23 In14d-9 from flaviplumus
"fl3"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)
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.

May be able to be bred in the laboratory.

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