Species 2v. C. athalassicus Cannings, 1975

Adult

Male: Coloration variable from pale to dark.
AR 3.92 - 4.43 (4.14); wing length 4.3 - 4.7 mm (4.5 mm); VR 1.04 - 1.09; LR 1.07.
Anterior tarsi without beard, but occasional long setae up to 6 times the tarsal diameter.
Frontal tubercles about 40 micron long.  Clypeus broad with 25-52 (42) setae.    Palp segments 2-5 (micron) 84 : 300 : 265 : 320).
Thorax with median tubercle as a low bump.  Setae: Acrostichals 0 - 5; Dorsocentrals multiserial 30 - 50 (39); Prealars 15 - 19 (16); Scutellars 42 - 70 (53).
Leg measurements (micron):
 
 
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
BR
PI
2180
1990
2130
1190
880
690
350
1.07
1.10
6.0(rare)
PII
2190
2120
1110
740
570
420
270
0.52
1.03
 
PIII
2480
2510
1550
980
740
470
290
0.61
0.98
 


Male hypopygium (left) and superior volsella (right) of a paratype of Chironomus athalassicus

Abdominal terga reddish brown with a thin dark basal band.  The apical one third to one half of segments 7 and 8 pale.  In higher salinities the colors become paler.
Anal point broad, inner edge of superior volsella only slightly curved and of the D(f) type. Inferior volsella relatively long and bending outwards at the end, reaching past the end of the anal point and to about the midpoint of the gonostylus which reduces relatively sharply over posterior quarter.

Female:  Color as male, but generally paler.
Wing length 5.0-5.2 mm; VR 1.10-1.14 (1.13) or 0.88-0.91 (0.97); ant. LR 1.12-1.15, mid LR 0.50-0.54 (0.52), hind LR 0.60-0.68 (0.63).
Antennal segments (micron) 200 : 150 ; 160 ; 150 ; 260, AR 0.36-0.43 (0.39); A5/A1 1.2-1.45 (1.3).  Frontal tubercles about 25 micron long.
Clypeus broad about 1.7x the antennal pedicel.  Palp segments 2-5 (micron) 80 : 225 ; 225 ; 345.
Thorax with median tubercle as a bump.
Setae: Acrostichals and postalars absent; Dorsocentrals multiserial 46-74 (56); Prealars 12-16; Scutellars multiserial 47-97 (62).
Genital lamina quadrate.

Pupa:  (Sexual differences not considered) Total length 10.0-13.8 mm (11.7 mm).  Frontal tubercles 240 µm long, conical and about twice as long as wide at base, subterminal seta about one third of length of tubercle at about 75 µm long.  Respiratory base 110x215 (HR 1.95).  Posterior row of curved hooks on segment II comprising 75-90 hooks over 0.7 of the segment width. .  Caudolateral spur of segment VIII with 6-9 closely applied spines; anal lobes with 115 - 125 irregularly biserial lateral setae.


Caudolateral spur of segment VIII of a paratype of Chironomus athalassicus

Fourth instar larva a medium to large (fem. 13.3-20.8 mm; male 17.0 mm) melanotus- or semireductus-type, ventral tubules short to moderate length, but apparently longer in lower salinity, where the posterior pair of tubules may have a slight coil at the end (saline - about 0.68-0.72 mm; fresh water - about 1.12-1.56 mm, and anterior generally longer).  Lateral tubules relatively short (80-240 µm).  Anal tubules about 2-3 (2.82) times longer than wide (len. 354-633 µm, width 127-228 µm) larger in saline conditions and ventral pair generally larger.
Gular region generally darkened in posterior 1/3 to 2/3, extending beyond the mentum width and edges about half the height, frontoclypeus pale, but darker around antennae and mouthparts.
Oesophageal opening 90.9 (71-98.5) µm long and 2.8-4.9 times longer than wide.
Mentum (Fig. a) with sharp teeth when not worn; c2 teeth relatively well separated (type III);  4th laterals reduced to about level of 5th laterals (type II).
Ventromentum (Fig. d) about 3.1-3.7 times wider than deep and 1.05-1.11 times the mentum width; with about 49.1 (45-54) striae; plates separated by about one third of the mentum width; VMR about 0.32-0.41.  Pecten epipharyngis (Fig c) with 10-17 essentially type B teeth.
Premandible with relatively broad inner tooth, about 3-5 times the width of the outer tooth which is narrow along all of its length.
Antenna (Fig. b) with A1 about 1/3 of Ventral head length, 3.35-3.53 times longer than wide, with RO just below the middle of segment; AR about 2.35 (2.24-2.45); antennal segment proportions (µm) 156 : 33 : 10 : 16 : 7 (Cannings gives segment 5 as the same length as segment 3).
Distance between the antennal bases sometimes larger than the distance between the S4 setae, which occupy 75-85% of the frontoclpeal width.
Mandible (Fig. e) with relatively pale third inner tooth almost separated (type IIB); about 19.6 (17-21) furrows on outer surface near base, 15 (13-18) taeniae in the Pecten mandibularis; Mdt-Mat 25-45.5 µm, MTR 0.25-0.42.

Cytology:  4 relatively short polytene chromosomes with the thummi arm combination AB, CD, EF, G.  Centromeres heterochromatic, forming a chromocentre in BC specimens from saline habitats.
Arm G relatively short and closely paired, with a nucleolus about in the centre.  Nucleoli also near the centre of arms B and D.
Polymorphism in arms B (only in males?), D and F.
Tentative banding patterns:
ath A1:    1 - 2c, 10 - 12, 3 - 2d, 9 - 4, 13 - 19                    i.e. as holomelas
athB1:    Nucleolus one third from centromere, puff (group 7) distal as in atrella
athB2:    inversion of about one third of arm near distal end.
athB3:    small inv. just distal of nucleolus.
athC1:    1 - 2g, 6b - 2h, 11c - 8a, 15 - 11d, 6g-h, 17a - 16, 7d-a, 6f-c, 17b - 22
athD1:    1 - 3, 11 - 18d, 7 - 4, 10 - 8, 18e - 24        i.e. as in longistylus, atrella
athE1:    1a - 3e, 5a - 10b, 4 - 3f, 10c - 13                              i.e. as cucini, plumosus, etc.
athF1:    1    -    23;                                                        i.e. Standard
athF2:    1a-d, 9 - 8d, 12 - 10, 2 - 3d, 1i-e, 3e - 4b, 13 - 14c, 8c - 4c, 14d - 23

Found: Alberta - Banff National Park; Elk Island National Park; Jasper National Park (all BOLD)
            British Columbia – Barnes Lake; Boitano Creek, and Boitano Creek, Riske Creek, and Lake Boitano (51.95°S, 122.13°W), Springhouse
            (Type locality) Jackson Lake; Sorenson Lake (all Cannings 1975); 10 Km W Kamloops (BOLD).
            Yukon Territory - Ivvavik National Park (BOLD).
            North Dakota – Clearwater Lake(48.50°S, 120.33°W), Mountrail Co.; Lake Isabel(46.819°S, 99.750°W), Kidder Co.

            Saline habitats in B.C., but N.D. sample from less saline situation.

Larva, pupa and adults described by Cannings (1975), who says the species is closest to C. atritibia.   This is C. sp. Is Andreeva of Kiknadze et al. (2004, 2010), the latter reference with a labeled karyotype.

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Modified: 13 April 2021
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