C. 'pseudoppositus' immatures

Larva a generally a medium sized bathophilus-type; length about 13.4 (10.2-15.30 mm (female); 11.45 (9.7-13.3) (male).  Ventral tubules well developed, posterior pair longer, length of anterior 0.68 - 1.20 mm; of posterior about 0.56 - 1 45 mm.  Gula varying from pale to posterior third darkened (generally paler in more northern populations), frontoclypeus generally pale or very slightly darkened.   Larvae are very difficult to distinuish from other members of the oppositus-group.
Mentum (Fig. c) with 4th laterals slightly reduced, sometimes to level of fifth laterals (i.e. between type I-II), and c2 teeth well separated, sometimes the c1 tooth is quite long (i.e. type III but can appear as IIA when worn).
Ventromentum (Fig. d) about 3.6 times longer than deep; 1.08-1.11 times the mentum width; with about 30-38 striae, VMR 0.23-0.33.    Pecten epipharyngis (Fig. a) with about 12-18 sharp teeth (i.e. type A of Proulx et al. 2013), occasionally with some reduced teeth.
Premandible with the normal two teeth, inner tooth two to three times the width of the outer.
Mandible (Fig. e) generally of type II, with about 14-17 furrows on outer surface at base.Basal segment of antenna (Fig. b) relatively long and narrow, about 3.5-4.5 times as long as wide; RO about 1/3 to 1/2 way up from base of segment; AR about 2.13 (1.89-2.31); A2/A1 about 0.22-0.27; A4/A3 about 0.9-1.3; segment proportions (micron) 124 : 31 : 9 : 12 : 7.
Distance between the antennal bases, 148.25 (114-166) usually greater than distance between S4 setae, 141.6 (119-154), but may be equal or even less in about 1/3 of specimens.
Mandible (Fig. e) generally of type IA or B, but may be IIB, with about 14.8 (11-18) furrows on outer surface at base; about 11-17 taeniae in Pecten mandibularis; Mdt-Mat 20-23; MTR about 0.28-0.36.

Cytology:  4 polytene chromosomes with the pseudothummi arm combination AE, BF, CD, G.    All chromosomes closely paired.
Arm G with a median nucleolus and two nucleoli, the large (probably) BR2 proximal of the nucleolus and the smaller BR3 near the distal end.  There appear to be two pieces of BR1, one between the nucleolus and BR2 and the other just distal of the nucleolus.  The potential site of BR4 is immediately distal to the BR1 fragment between the nucleolus and BR2.  Nucleolus in arm F at about group 19.
Polymorphism in arms A, C and D, that in chromosome CD associated with the MD (Martin & Lee 1984).
Possible small deletion heterozygous at distal end of arm G in one specimen.
psoA1:    1a-e, 6e - 7, 13 - 14c, 3i-f, 9 - 8, 2d - 3e, 1f - 2c, 10 - 11, 6d - 4, 12a-c, 14d - 19    i.e 14c-12c and then 6e-11 from oppA4
psoA2:    about 1a-e, 6e, 3e - 2d, 8 - 9, 3f-i, 14c - 13, 7d-a, 1f - 2c, 10 - 11, 6d - 4, 12a-c, 14d - 19
psoB1:    Sequence as B2 of oppositus
psoC1:    as C. tepperiC1
psoC2:    Sex linked and only as heterozygote in some males; generally includes D2
psoD1:    1-2e, 6-8, 19a-c, 14h-16, 2i-g, 18a-g, 12-10d, 3a-d, 9e-b, 2f, 5-3e, 10a-c, 17a-f, 9a, 13-14g, 19d-24    i.e. inv6-2f from tepD1
psoD2:    includes C2; sex linked and only as heterozygote in some males
psoE1:    1 - 3e, 10b - 3f, 10c - 13                                                                                    as oppositus E1
psoF1:    1 - 2a, 10 - 2b, 11 - 23                                                                                      as oppositus F1
psoG1:     Median nucleolus with a BR on either side of it.

Nucleoli and location of C-bands studied by Lentzios & Stocker (1979) and Lentzios et al. (1980) as C. alternans b.

Pupa:  Length about 8.4 mm.  54 hooks in row on segment II,  1-2 spines on caudolateral spur of segment VIII; 86 filaments on each side of the swim fin.

A colonizing species, often found in relatively small artificial containers, shallow ponds and creeks.

See also C. 'pseudoppositus' adult;  C. oppositus immatures.

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Modified: 21 November 2021
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