Species 2g. Chironomus "butleri"

Named for Malcolm G. Butler who published a chromosome photo of the species.

C. decorus-group species 2 - Butler et al. 1995

In BOLD Bin: BOLD:AAB7030.
C. decorus and C. quinnitukqut are also in this Bin.

Adult:

Male (based on Mississippi specimen)
Wing length:  4.0 mm.  Wing width:  0.96 mm.  VR 1.0.  Scf on brachiolum 3, 4.  Setae on squamal fringe 33, 36.  Cross vein and posterior fork slightly darkened.
Antennal ratio:  3.01.  Frontal tubercles developed, about 56-58 micron and 2.6 times longer than wide.  Clypeus about 0.7 of diameter of the antennal pedicel, with about 29 setae.
Setae:  Achrostichal - 29;  Prealar - 7;  Dorsolateral - 33; Scutellar: anterior - 23; posterior - 18 (total 41).

Legs with darkening of the joints of the anterior tarsus and tibia.
Leg lengths (in microns) and proportions as below:

 
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
BR
PI
1490
1450
2050
1065
800
680
325
1.39
1.03
3.0
PII
1585
1440
920
510
360
270
190
0.64
1.10
 
PIII
1661
1694
1199
653
510
300
188
0.77
1.01
 
Note that for PI, Ta4 is shorter than Ta3 (about 85%).

Abdomen:    with saddle spots on TII-Vi, then whole segment darkened, about 10 setae in a single pale spot on tergite IX.


Male terminalia of C. "butleri".
A typical C. decorus-type hypopygium.

Superior volsella generally of the D-type, but some specimens tend to that of C. cingulatus, which Strenke (1959) classes as an E-type.  Inferior volsella with simple setae; extending about to the end of the anal point or 1/3 of the gonostylus length and slightly turned out at the distal end; gonostylus only slightly widened in the middle, but narrowing markedly over posterior 1/2 to 1/3.

Female (based on Mississippi specimen)
Wing length:  4.1 mm.  Wing width:  1.3 mm.  VR 0.99; abt 53 setae in squamal fringe, 3-4 SCf on brachiolum.
Head: Cephalic tubercles abt 46x23 µm (2.0 times longer than wide).  Clypeus abt. 2.1 times wider than the diameter of the antennal pedicel, with about 51 setae.  Antenna missing save for A1 which is 225 µm long.
Thorax: Setae:  Achrostichal 17+;  Humerals 5-9 in group +2-3 linear; Dorsolaterals 43 (dorsolaterals plus humerals 51-54); Prealar - 6,7; Supra-alar 1; Scutellar 39 (21 in anterior row, 18 in posterior row).

Leg lengths (in microns) and proportions as below:

 
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
BR
PI
1390
1290
-
-
-
-
365
-
1.08
1.5
PII
1620
1490
860
430
340
235
180
0.58
1.09
 
PIII
1730
1750
1280
740
580
320
210
0.73
0.99
 
at least 72 SCh on hind Ta1

Most of tergites II-VIII darkenend.  About 10 setae on Seg. X, which has a central oval area with width 0.31 of the total length; 3 setae on GpIX.

Pupa: Brown cephalothorax and generally pale (yellowish) abomen.  Shagreen over the posterior 3/4-4/5 of TII-VI, more extensive in midline.
Female abt 9.5-9.6 mm; male about 9.75 mm. in length.  Inner margin of wing case 1.64-1.70 mm.  Cephalic tubercles large, 114-121 µm long and 1.2x (fem) or 1.65 (male, Fig. below) longer than wide; with seta at least 51 µm long.  No secondary tubercles.  Respiratory scar about 127-170 µm long and HR about 1.7-2.0.
Hook row of seg. II with about 110 (94-125) hooks, and occupies abt 0.58-0.81 of segment width.  Pedes spurii A of segment IV abt. 119-245 µm long and 58-101 µm wide, occupying 0.13-0.28 of segment length.  L-seta at junction of segments III/IV at least 76 µm long, that of IV/V not seen.
Caudolateral spur of segment VIII with about 7.7 (4-11) closely applied spines, some arising lower than the head of the spur.  About 98.3 (84-112 taeniae on margin of swim fin, in 2-3 rows.

Fourth instar larva a medium sized bathophilus-type, but sometimes a melanotus-type with posterolateral tubules up to about 130 µm long.  Length abt. 9.5-20 mm, female; 12.5-17.5 mm, male;  Ventral tubules may be of fluviatilis-type, with anterior pair usually slightly longer (ant. 1.16-1.7 mm; post. 0.85-1.5 mm).  Anal tubules about 340-600 µm long and about 2-4 times longer than wide.
Over 2/3 of gular region dark and extending higher at the edges than in the midline and widest anterior to the posterior margin, and frontoclypeus pale.  Oesophageal opening long, about 71.2 (63-81 µm) and about 3-4.2 times longer than wide. Oesophageal opening long, about 71.2 (63-81 µm), and narrow, about 3-4.2 times longer than wide.
Mentum (Fig. a.) with somewhat rounded teeth; c1 tooth tall and relatively broad, c2 teeth moderately well developed (type IIA or III); 4th lateral teeth slightly reduced, almost to level of 5th laterals (type II), although Hilsenhoff & Narf (1968) express that the 5th laterals are raised; 6th laterals generally arising below the level of other teeth.
Ventromental plates (Fig. c), 3.1-4.0 times wider than deep; 1.0-1.1 times the mentum width; distance between the plates about a third to a half of the mentum width, with about 34.7 (32-39) striae; VMR 0.25-0.33.  Pecten epipharyngis (Fig. d) with about 14.1 (12-16) relatively blunt teeth (type B), lateral teeth smaller and narrower.  Premandible with inner tooth relatively broad, about 2.5 to 3.5 times wider than the outer tooth which tapers to a relatively fine tip.
Basal segment of antenna (Fig. b) relatively short - only 0.34-0.43 of the VHL, about 2.6-3.7 times as long as wide; RO a third to a half up from base of segment; fourth segment almost twice the length of segment 3; AR 2.34 (2.1-2.7); relative length of segments (micron): 131 : 28 : 7.5 : 11.5 : 6.
Distance between antennal bases (144-213 µm) greater than distance between S4 setae (129-200 µm), which are separated by 80-90% of the FC width at that point.  S5 setae varying from slightly posterior to slightly anterior to the nearby RO.
Mandible (Fig. e) of type IIA or B and with about 17.1 (13-21) furrows on outer surface near the base; Mdt-Mat 35.2 (30-45) and MTR 0.42 (0.39-0.45).

Cytology:  4 polytene chromosomes with the thummi arm combination AB, CD, EF, G; centromeres not heterochromatic.
Arm G usually paired only at the end away from the virtually terminal nucleolus; 2 Balbiani rings (BRs) developed - one near the middle, the other near the other end of the arm.  No nucleoli in the long chromosomes.
Polymorphism in arms A, B, C, F and G - polymorphism may be more common in populations in the northeast.

butA1:    1a-e,7c-4c, 3i-f, 17a-h, 12c-10, 2c-1f, 15-16, 3e-a, 14-13, 4a-b, 2k-d, 9-7d, 18-19                            (Kiknadze)
butA2:    Simple inversion
butB1:    Puff near distal end of arm, with dark bands proximal (group 8 and 7).
butB2:    Complex inversion.    Dark bands distal to puff (groups 7 and 8).
butC1:    1a-e, 3c-2f, 4a-6b, 12b-14c, 12a-11d, 6gh, 17a-16, 7d-a, 6f-c, 17b-18, 15-14d, 1f-2e, 8-11c, 19-22              (Kiknadze)
butC2:    Inversion of about half the arm towards distal end.
butD1:    1 - 3e, 17 - 18d, 14f - 10d, 14g - 16, 21 - 18e, 10c-a, 7d - 3f, 9 - 7e, 22 - 24                                              (Kiknadze)
butE1:    1 - 3e, 5a-e, 10e-c, 3f - 4, 10b - 6a, 10f - 13
butF1:    1a-i, 9 - 2, 13c - 17, 10 - 11d, 13b - 11e, 18 - 23                                                                                          (Kiknadze)
butF2:    Inversion of about 1/3 of arm distal to center.
butG1:    Virtually terminal nucleolus, central and distal BRs
butG2:    Small inversion distal of the distal BR

DNA analysis:
mtCOI:  Barcode sequence shows that this species is very close to C. decorus (sp. 3a), as both are placed in BOLD Bin AAB7030.  Comparison of the sequence to that of C. decorus indicated only a single base pair difference in the COI sequences, while other differences exist as polymorphisms in this species.  C. quinnituqut is also in the same BOLD Bin, but here there are 13 consistent base differences between the species (with 3 of these including a low level of polymorphism for the base in the other species).

Base
C. quinnitukqut
    G    A    T    T   A/T     G    C    T    A    A     T      T     C
C. 'butleri'
     A    G    C    C     A     T     T    C    G    G    C/T   C    A/T

Found: Ontario – Cactus Field, Point Pelee Natl. Pk. (41.939°N, 82.516°W) (from GenBank)
              Quebec - St. Charles River (46.82°N, 71.22°W), Quebec City; Lake Adéline (48.20°N, 79.17°W), Lake Dufault (48.28°N, 79.00°W),
               Lake Duprat (48.33°N,79.12°W), Lake Fortune (48.18°N, 79.32°W), Lake Opasatica (48.17°N, 79.33°W), all Rowyn-Noranda.
              Saskatchewan – Lake Waskesiu (53.92°N, 106.08°W), Prince Alfred National Park.
              California – Lake Davis (abt 39.70°N, 120.50°W).
              Indiana: – Crooked Lake, Angola; Lake Oneotta, Marinette(?); Shafer Lake.
              Kansas – Lone Star Lake (38.83°N, 95.38°W); Natural History Reserve, University of Kansas (39.00°N, 95.42°W),
              both Douglas County.
              Massachusetts – Connecticut River, Northfield (42.691°N, 72.452°W), Franklin Co. and at Northampton (42.322°N, 72.638°W),
              Hampshire Co.
              Michigan: – Saginaw Bay (43.75°N, 83.67°W), Lake Michigan.
              Minnesota: – Lake Christina (45.08°N, 95.75°W), Douglas Co.
              Mississippi – Belzoni (33.17°N, 90.67°W), Humphreys Co.; Jackson (32.50°N, 90.33°W), Hinds Co.
              New Mexico – Springer Lake, Colfax Co.; Frio Draw and Weber City cut-off, Curry Co.; Canadian River and Ute Lake, Quay Co.
              Texas - Quaker Street Plaza, Lubbock (33.64°N, 101.96°W), Lubbock Co.
              Vermont – White River (43.80°N, 72.45°W), nr, Sharon, Windsor Co.
              Wisconsin – Booth Lake; Friebauer Lake, Bayfield Co.; Lake Oneonta, Marinette Co.; Lake Pepin, Pepin Co.; Pine Lake, Oneida Co.;
               Booth Lake, Walworth Co.
              Brazil.

Found mostly in depths to over 10 m. in lakes.
It is possible that those from shallow habitats are actually C. decorus (sp. 3a).

This is the C. attenuatus of Hilsenhoff & Narf 1968 and C. decorus-group species 2 of Butler et al. (1995), who provide a karyotype photograph.  Wuelker et al. (2009) give some cytological comparisons to C. bifurcatus and C. blaylocki.

See also  C. bifurcatus,  C. blaylocki,  C. decorus Joh.,  C. harpi,   C. mozleyi,   C. winnelli,  C. sp. b,  C. sp. c,  C. sp. j,  C. sp. 2a,   C. sp. 2b,  C. sp. 3h,  C. sp. 3i,  C. sp. 3j.

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Modified: 22 July 2021
Access: Unrestricted
Copyright © 2000-2021, Jon Martin.