North American Chironomus: C. sp. 4m

Species 4m C. sp. 4m.

Adult: not known.

Pupa: not known.

Larva a medium=sized plumosus-type  Slightly dark gular region and frontoclypeus.  Ventral head length 310.5 µm.  Clypeal aperture 86 x 30 µm, 2.8 times wider than deep.  No information on anal tubules.
Mentum (Fig. a), 195 µm wide, with 4th laterals reduced virtually to level of the 5th laterals (i.e. type II), and center trifid tooth with c1 broad and the c2 teeth relatively well separated (i.e. type IIA).  VPA (ICD) 55.5 µm, 0.29 of mentum width
Ventromentum (Fig. c) with about 40-41 striae, plates separated from each other by about 0.3 of the width of the mentum.  Pecten epipharyngis with about 19 teeth.  Width between antennal bases (157 µm) greater than that between S4 setae (131.5 µm) which are separated by 0.73 of mentum width at that point.  S5 setae sl. anterior of nearby RO.  Premandible with narrow teeth, inner tooth about 4.4 times width of outer tooth (perhaps type B).
Antenna (Fig. b) with basal segment about 4.2 times as long as wide; AR about 1.83; ratio of segments (micron) 133 : 38 : 12 : 14.5 : 8.  RO abt 0.42-0.45 up from base on segment.
Mandible (Fig. d) about 255 micron long, with third inner tooth well developed (Type III), 15-16 taeniae in Pect. mad. and about 12-13 striae on inner margin near the base; MTR abt 0.33-0.37.

Cytology: Not completely certain, but most likely candidate at the only known locality is a pseudothummi-cytocomplex species, i.e. 4 polytene chromosomes with arm combination AE, BF, CD, G.
Arm G paired at the median nucleolus, no nucleolus in long chromosomes. Puff not formed in arm B; characteristic band group (25-27) in normal position close to centromere.

Arm A1 probably 1 - 2c, 10 - 12, 3 - 2k-d, 9 - 4, 13 - 19 ie. as in holomelas
Arm E1: 1a - 3e, 10b - 3f, 10c - 13g; ie. as in aprilinus, luridus, riihimakiensis, etc.
Arm G1: Shows some similarities to the 'amphora-type' arm G of the riihimakiensis-group but with an inversion reversing the location of the nucleolus and a BR.

Found: Alaska - Potter Marsh, Anchorage Co.

Larva collected by Dave Wartenbee; thorax taken by Iya Kiknadze, head and rest of larval body by Jon Martin. Unfortunately the original coordinated labelling became lost, but this combination of cytology and morphology is the only one not accounted for amongst the Potter Marsh samples.

Mitochondrial COI sequence indicates that this is a species that has not been barcoded previously, with relationships to pseudothummi-cytocomplex species.

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