Species 3i.  C. decorus group?

Only 3 larvae are known for certain.


This specimen not necessarily associated as other species were also present.

Male terminalia of C. ?sp. 3i (left) and superior appendage (right)

About 6 setae on TIX, possibly in separate pale areas.  Anal point relatively broad.  Superior volsella of E-type (g) of Strenzke (1959) - i.e. as C. cingulatus; Inferior volsella about as long as the anal point and to about 1/3 of the gonostylus, which narrows relatively sharply over distal third.

Female: Not known.

Pupa:  Not known.

Fourth instar larva a medium sized plumosus-type (about 10.1-15.3 mm);the larva from Sudbury was the smallest, but it was also parasitised.  Ventral tubules relatively long, posterior pair longer (ant. 1.20-2.64, post. 1.30-2.86 mm).  Gular region slightly dark to dark on posterior1/3-1/2, slightly wider than the mentum and widest at the posterior margin; frontoclypeus pale.  Oesophageal opening 63-83 µm wide and 3.3-4.2 times wider than deep.
Mentum (Fig. c, below) with somewhat rounded teeth, probably due to wear, c2 teeth of centre trifid tooth not well separated (type IA-IIB and III at Sudbury); 4th laterals reduced (type II-III).
Ventromentum (Fig. d, below) about 171-187 µm wide, 3-3.4 times wider than deep, and 1.02-1.04 times the width of the mentum; with 36-43 striae; VMR 0.29-0.32.  Pecten epipharyngis (Fig. a, below) with about 11-12 sharp but broad teeth (type B).
Premandible with inner tooth relatively narrow, 3.4-4.5 times wider than the outer tooth, both teeth narrowing to a point.
Antenna (Fig. b, below) with A1 relatively short, only about 0.33-0.35 of VHL; about 2.92 (2.71-3.19) times longer than wide, RO about a quarter to half way up from base; AR about 1.9 (1.75-2.12); antennal proportions (micron) about 103 : 28 : 7 : 11.5 : 7 ; i.e. A5 is only slightly shorter or longer than segment 3.
Distance between the antennal bases (144 µm) on average the same as that between the S4 setae (144 µm), which occupy about 81-91% of FC width, but may be geater or smaller.  S5 setae either level with or slightly posterior to nearby RO.
Mandible (Fig. e, below) 207-243 µm long, with third inner tooth at most partly separated and partly colored (type I-IIB); 16.5 (15-18) furrows on the outer surface at the base; 13.2 (10-16) taeniae in PecM; Mdt-Mat about 20-30 µm when not badly worn; MTR 0.28-0.43.

Cytology:  4 polytene chromosomes with thummi arm combination AB, CD, EF, G.
Centromeres obvious but not markedly heterochromatic.
Arm A with groups 4-6 approximately as in pigA1 (could be groups 1-6 at that end); arm B with bulb (gp 7?) in proximal third, but apparently separated from the dark bands of group 8.  Distinguishing bands of arm C about the middle of the arm.
Arm G closely paired with 2 Balbiani rings near middle of the arm.  Nucleolus in arm D near centromere.

Arm E:    1 - 3e, ?? 7 - 6, 9 - 8, 12 - 13
Arm F:    ?? 13 - 11, 16 - 23

Found: Ontario - 4 m E. Sudbury(46.52°N, 80.90°W).
            Pennsylvania - vicinity Pittsburgh (40.43°N, 79.97°W), Allegheny Co.

Pools or small streams.
This species was not found in the Proulx et al. (2013) samples from the Sudbury area, possibly because these were samples from lakes.

Shows some similarities to C. stigmaterus, which might indicate that the male (above) belongs to that species (although the species has not been recorded from Canada). The larva can be distinguished by the normally darkened FC; longer A1 (3-3.94 longer than wide) and the more fully developed 3rd inner tooth of the mandible of C. stigmaterus.  It also shares the only nucleolus being near the centromere of arm D, but other sequences, particularly arm A are different.  The only other known Nearctic species with a nucleolus in arm D is C. utahensis, which is considered a member of the cytological C. decorus group, but not morphologically similar (Wülker, Sublette & Martin, 1991).

See also  C. bifurcatus,  C. blaylocki,  C. decorus Johannsen,  C. harpi,  C. mozleyi,  C. winnelli,  C.sp. b,  C. sp. c,  C. sp. j,  C. sp. 2a,  C. sp. 2b,  C. 'butleri',  C. sp. 3h,  C. sp. 3j.

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Modified: 17 August 2021
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