Asian Chironomus: C. sulfurosus

Chironomus fusciceps Yamamoto 1990

as new name for Chironomus lugubris sensu Tokunaga 1938,
and Sasa & Yamamoto (1977).
Also called Chironomus thmini (misspelling of thummi?) Tokunga 1940
and Chironomus riparius Sasa & Yamamoto 1977.

In BOLD Bin: BOLD:ACH4992
Also includes a specimen of C. sulfurosus, which has 99.83% homology.

(based on Yamamoto 1990)

Adult:

A dark species, similar in coloration to C. acerbiphilus and C. sulfurosus but legs and anterolateral margin of scutum paler.

Male:
Wing length 1.8- 2.6 mm, width 0.6-0.8 mm. VR 0.91 (0.88-0.93). Squama with 10-20 setae.
Head: AR 2.40 (2.15-2.67). Frontal tubercle about 12.5-30 µm long, 10-15 µm wide.
Palpal proportions: 52 : 62 : 164 : 164 : 208; P5/P4 & P5/P3 1.27.
Clypeus with 30-39 setae.Thoracic setae: Antepronotum without setae; acrostichals 6-16; dorsolaterals 15-27; prealars 5-7; supraalar 1; scutellars 13-30 (biserial).
Leg proportions (micron):

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta5/Ti
PI	1280	980	1460	730	610	470	270	1.43-1.52	1.31	0.28
PII	1290	1100	570	340	270	200	170	0.51-0.53	1.17
PIII	1420	1260	800	450	380	240	170	0.63-0.65	1.13

At least 6 setae on TIX (only part shown).
Genitalia resembling that of C. acerbiphilus but S-type Superior volsella much stouter with 6-8 setae on base; anal point narrower at base; Inferior volsella with 20-29 long recurved setae on apical half; gonostyle moderately swollen and narrowing markedly over distal third, with 6-8 apical setae.

Female
Coloration almost the same as the male.  Cercus brown.
Head: Antennal proportions: 134 : 88 : 106 : 100 : 244.  AR - 0.57; A5/A1 – 1.82Frontal tubercle 12.5-17.5 µm long and 10.0-15.0 µm wide.
Palpal proportions (micron): 56 : 68 : 172 : 170 : 232; P5/P4 1.36; P5/P3 1.35.  Vertex with 23-25 setae; Clypeus with 29-40 setae.
Wing length 2.2-2.9 mm, width 0.8-1.0 mm.  VR 0.85 (0.76-0.89); squama with 14-24 setae.
Thoracic setae: acrostichals 9-18; dorsocentrals 19-34 (not known if this includes the humerals); prealars 6-9; supraalar 1; scutellars 21-41.
Leg proportions (micron):

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	Ta4/Ti
PI	1370	1000	1420	690	590	470	280	1.32-1.52	1.37	0.28
PII	1360	1160	590	330	260	200	160	0.49-0.54	1.17
PIII	1460	1320	510	450	390	240	190	0.60-0.62	1.11

Genitalia almost the same as in C. acerbiphilus, but segment X separated from TIX by a slender membranous area. Laterosternite with 3-7 setae, Segment X with 9-18 setae.

Pupa: Body dark brown, length 4.5-6.5 mm. Cephalic tubercles acutely pointed, with subapical spine. Abdominal segment II with a row of about 60 hooks, pedes spurii B developed. Postero-lateral spurs of segment VIII with 1-2 spines. Chaetotaxy and shagreen as shown in his figures.

Fourth instar larva:  A small (length 10 mm) thummi(?)- or bathophilus-type larva, i.e. lacking lateral tubules.  Anal tubules well developed, of a single lobe, dorsal pair shorter than the ventral pair, which are about 3/4 the length of the posterior pseudopods.  Head uniformly dark brown.
Mentum of type I, in fact Yamamoto’s illustration suggests that the 5th and 6th laterals are reduced, central tooth could be type IB.  Ventromentum not described and illustrated by olny a vague outline, which indicates they are longer than the mentum width.
Pecten epipharyngis with about 20 uneven but pointed teeth, suggesting possibly type B.  Premandible with 2 teeth, outer tooth shown as much longer than the inner tooth which is 3-4 times wider..
Antenna with 5 segments, relative lengths of segments 42 : 10 : 2 : 4: 2 ; segment A1 with a ring organ at basal 2/5.  Antennal blade long, reaching the base of 5th antennal segment, accessory blade indistinct.  AR about 2.3.
Distance between the S4 setae greater then that between the antennal bases.Mandible possibly of type IIIC, furrows not recorded; 3 spines on inner margin; Pecten mandibularis with 10 taeniae.

Cytology: no information, but if related to C. acerbiphilus is likely to be pseudothummi cytocomplex.

Found in sulphur-containing water.

Found: Japan - Mount Unzen, Nagasaki Prefecture, Kyushu. (Type locality).
Also found Japan>: - Tarutama, Kumamoto Prefecture. Kyushu.

DNA sequence: There is one accession from GenBank which could be this species.
Other sequences from GenBank or BOLD appear to be misidentified:
GenBank accession number AB704937 is actually for a species of Kiefferulus
That in the BOLD database (in BOLD Bin: BOLD:ACH4991) appears to be a species of Glyptotendipes, possibly G. tokunagai.

Noted by Yamamoto (1990) to be closely related to C. acerbiphilus and C. sulfurosus.The adult can be distinguished from C. acerbiphilus by the higher LR, and the male from C. sulfurosus by the more slender anal point.
The larva can be distinguished from C. acerbiphilus and C. sulfurosus by the uniformly dark head capsule.

DNA analyses:

If correctly identified, the barcode for C. sulfurosus has 99.73% homology, while C. acerbiphilus is in a different BOLD Bin: BOLD:AAJ4234.

MtCOI: there are sequences in GenBank: Accessions AB704938 and LC377640 (mined to BOLD database).

[ See also C. acerbiphilus ; and C. sulfurosus]

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