South East Asian Chironomus: C. strenzkei

Chironomus strenzkei Fittkau 1968 (was C. striatipennis type 2 of Pramual et al. 2016)

In BOLD Bin: BOLDAAD2474
Under incorrect names

The taxon 'C. striatipennis Ty. 2' was first recorded by Pramual et al. (2016). Subsequent analysis of the BARCODE COI sequence revealed that it was identical to that of C. strenzkei. As there was no valid binomial name for this taxon, it becomes C. strenzkei, which is therefore not a synonym of C. striatipennis or C. kiiensis as previously claimed.

Adult:

Male:
The abdomen of C. strenzkei (see below) is similar to that of C. striatipennis and C. kiiensis.  The laboratory reared specimens from the Plön colony are larger than those collected in the wild.
Wing length about 2.27 (1.56-2.64) mm, width 0.64 (0.55-0.73) mm.  VR = 1.08 (1.04-1.14).
AR about 2.49 (2.10-2.95).  Frontal tubercles developed, about 62 (35-68) µm long and 18.3 (15-22) µm wide.  17-18 setae on clypeus; palpal proportions (µm) 52 : 38 : 139 : 154 : 243; P5/P4 1.53-1.63; P5/P3 1.58-1.96.
Thoracic seta: acrostichal - 10-13; dorsocentral - 16-18; prealar – 4-5; supraalar 1; scutellar in two rows, anterior - 4-7, posterior - 9-11 (total 14-16).
Wings with dark spot over the crossvein and with obvious dark clouds and seams, particularly in cell R5, as in C. striatipennis; abt 6-14 SCf on brachiolum in two clusters, abt 18 setae in squamal fringe.

Leg lengths (micron)and proportions:

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	BR
PI	1031	938	1390	760	613	413	249	1.32-1.64	1.10-1.11	2.3-3.5
PII	1092	1048	735	366	266	175	136	0.60-0.82	1.01-1.07
PIII	1224	1270	987	557	430	256	170	0.78	0.96

BR 2.3-3.5, i.e. apparently lower than in C. striatipennis.

Setae of tergite IX possibly in individual pale areas (possibly trianglar).
Superior volsella of the E(h)-type of Strenzke (1959). Anal point narrow at base and expanded at tip. Inferior volsellao reaching about to end of anal point. Gonostylus moderately swollen and reducing markedly over distal half.

Male hypopygium (above) and details of the Inferior volsella and anal point (below)

Female not described.

Pupa: Length 5.5-7.5 (Fittkau 1968).  A single male pupal exuvia from the Plön culture was available for more detailed analysis.
Length 6.26 mm; posterior margin of wing case 1.35 mm.; Cephalic tubercles 85x65 µm.  Respiratory base 133x63.5 µm; HR 2.1-2.2; with a line of irregular small humps lateral to it.  About 85 recurved hooks, occupying 0.76 of the segment width, at the posterior margin of segment II.
Pedes spurii B laterally on segment II; Pedes spurii A on segment IV about 131x89 µm, abt. 0.24 of segment length; caudolateral spur of segment VIII with 1 & 1+1 small spines, the single spine with a broad shoulder.  Swim fin with 75-95 taeniae, initially in a single row, then up to 3 rows.
Shagreen light over whole of segments II-V, waisted on VI, pale anterior on VII, 2 lateral segments on VIII.

Pupal cephalic tubercles (above) and spur (below) of C. strenzkei

Fourth instar larva: a small plumosus-type of length 9.2-10.8 mm (fem. abt. 9.2 mm; male 9.5-10.8).  Anterior ventral tubules bent and posterior ventral tubules coiled with posterior longer (ant 0.74 mm, post 0.78.mm). Lateral tubules 220 µm; anal tubules rel. long: dorsal 350 x 120 µm (l/w 2.9); ventral 380 x120 µm (l/w 3.2).
Gula of this Malaysian specimen dark, extending over posterior 2/3; and frontoclypeus also darkened.
Mentum with c2 teeth of central tooth separated and sharp (type III), 4th lateral possibly slightly reduced, but broken on available specimen (type 1?).  Pecten epipharyngis with about 14 teeth.
Ventromental plates 175 µm wide and 3.45 times wider than deep; separated by about 0.28 of the mentum width, about 38-40 striae reaching at least halfway to anterior margin; VMR 0.28; 1.08 times the mentum width.
Premandibles with teeth approximately equal in length, inner coming to a rounded point, outer to a sharp point (type B1); inner tooth about 3.2x wider than the outer tooth.
Antenna with basal segment relatively long, 3.2 times longer than wide; RO from about 0.37-0.42 up from base of segment; AR about 1.8; proportions (µm) 102 : 23 : 9 : 11 : 8.  Distance between antennal bases (121 µm) less than the distance between the S4 setae (126.5), which occupy about 0.81 of width of Frotoclypeus at that point.
Mandible with third inner tooth partially separated, and pale (i.e. type IIA), with 19-20 furrows; 11 taeniae in Pecten mandibularis; Mdt-Mat 28 µm; MTR 0.37.

Cytology:  Four polytene chromosomes with the pseudothummi-cytocomplex combination BF, CD, AE, G (Wülker & Morath 1989).  While obviously close to C. striatipennis, there are some significant differences.
Nucleolus near end of arm G.  Centromeres of the longer chromosomes slightly heterochromatic.  No other details clear.
Arm G closely paired with a subterminal nucleolus, which may have a very close BR.  No nucleoli in the long chromosomes.  In Asia, the species is highly polymorphic.
stzA1:  1 - 2c, 11 - 7, 4 - 6, 2d - 3, 12 - 19
stzB1:  Bulb of group 7 not obvious but possibly a puff at distal end.
stzC1:  no sequence available.
stzD1:  no sequence available.
stzE1:  1a - 13g            i.e. Standard (as striatipennis)
stzF1:  1 - 2a, 15e - 11f, 2b - 15f-a, 11a-e, 16 - 23
stzG1:  subterminal nucleolus, with BR nearby; no other BRs visible in available specimens.  The BR does not appear to be present in C. striatipennis

Whole complement (above) and arm G (below) of C. strenzkei

Found: BRAZIL - Manaus, Amazonas (Type locality)
Malaysia - Minden, Penang (5.13°N; 100.13°E)
Singapore - Bedok Canal (1.367°N; 103.939°E)
Thailand - Pattani, Pattani Province (6.87°N; 101.25°E)
Japan
U.S.A. - El Segundo, Los Angeles Co. California.

Adult and immatures described by Al-Shami et al. (2012) as C. kiiensis may refer to this species.

Molecular: The mitochondrial COI differs from that of both C. striatipennis and the sequence of the common form of C. kiiensis, as well as the recently identified taxa C. nr. kiiensis and C. kiiensis kMYTH. The sequence is found in Japan and SE Asia, but has not been found in India. The sequence of C. strenzkei is identical to that of this species, and since this taxon has no formal name, it becomes C. strenzkei (i.e. that species is not a synonym of any other member of this group).
GenBank accession numbers: KJ424334-KJ424336. BOLD accession numbers: COTW009, COTW010, COTW013
The COI sequence differs from that of C. striatipennis at 7 bases, from C. kiiensis at 11 bases, from C. kiiensis form kMYTH at 11 bases, and from C. nr.kiiensis at 31 bases.