Chironomus vitellinus immatures

Fourth instar larva:  a medium sized, essentially plumosus-type larva, although lateral tubules (437 (320-800) µm long are more ventrally placed than in other species.  Length 11.5 (9.2-13.7)(female) 9.75 (9-13.7)(male) µm and VT long, anterior pair 1.49 (0.8-2.48) µm generally longer than posterior pair 1.28 (0.70-2.16) µm.  Anal tubules with median constriction, dorsal about 500 µm long and 3.6 times longer than wide; ventral 330 (220-440) µm long and 3.4 times longer than wide.  Salivary reservoir 76 (56-88) x 18 (15-20) µm and 4.2 (3.1-5.3) times wider than deep.
Gula pale (in Malawi) or slightly darkened on posterior third (in other areas), slightly wider than mentum width and widest at the posterior margin; FC pale.
Mentum (Fig. c) with the central trifid tooth set below the 1st laterals (although not always obvious if the 1st laterals are worn), and the c2 teeth markedly separated from c1 tooth (type IIA) and pointed towards it; 4th laterals at most slightly reduced (type I).  Pecten epipharyngis (Fig. a) with about 16.2 (15-17) teeth (type B) or sometimes irregular teeth (Type D).
Ventromental plates (Fig. d) about 171.4 (159-183) µm wide and 3.81 (3.6-4.0) times wider than deep and 1.15 (1.10-1.21) times the mentum width; separated by about 0.39 of the mentum width, with about 33.6 (31-36) striae; VMR 0.27 (0.20-0.33).
Antenna (Fig. b) with the basal segment about 3.4 (2.9-3.4) times longer than wide and about a third of the ventral head length; AR about 2.46 (2.34-2.57); ratio of segments 108.5 : 25 : 4.5 : 8 : 5. Distance between the antennal bases, 143 (129-152) µm, larger than that between S4 setae, 124 (106-143) µm.  S5 setae mostly slightly posterior to nearby RO.
Premandible (right)with 7 progressively reducing teeth.
Mandible (Fig. e) about 215 (201-243.5) µm long, with third inner tooth darkened and completely separated (type IIIC), with three spines on inner margin, and about 10.7 (10-12) furrows on the outer surface at the base; Mdt/Mat about 24 (12-28) µm, MTR 0.42 (0.31-0.47).

One of these larvae (MYA.1.3 BMAES 11F) from the region where both species occur, while clearly having the morphology of C. vitellinus, has the BARCODE sequence of C. javanus, indicative of hybridization involving a C. vitellinus male parent but a C. javanus female parent.

Pupa:  Illustrated by P.S. Cranston in his Electronic Guide to Chironomidae of Australia, (Cranston, lower figure):
Length: Male 6.38 (6.38-6.70) mm; female 7.01 (6.90-7.14) mm.  Exuviae grey.  Cephalic tubercles ((Fig. g, lower)) 86.3 (81-110) µm long and 56.5 (51-70) µm in diameter, subapical seta about 56 (38-90) µm long, i.e. about as long as the Cephalic tubercles.
It is possible there is slight development of frontal warts (see ((Cranston figure g lower)).
Respiratory base (Fig. h, lower) about 132.7 (119-157) x 62.25 (51-81) µm wide; HR 2.16 (1.94-2.35).  2 pairs of precorneal setae.
Abdomen (Fig. e, lower) with Pedes spurii A caudolateral on segments IV-VI, that on segment IV about 145 (116-157) x 89 (71-111) µm wide and about 22 (18-24)% of the segment length; PSB basolateral on segment I and small caudolateral on segment II, which also bears a caudal row of about 66.2 (54-81) hooks which occupy 58-68% of the segment width.
Caudolateral spur (Fig. f, lower) of segment VIII usually with 1+2sm (1-4) spines, although commonly only 1 is long.  Swim fin with about 70.29 (61-78) taeniae in two rough rows (particularly distally).

Cytology:  4 polytene chromosomes with the thummi-cytocomplex combination AB, CD, EF, G.  Subterminal nucleolus in arm G, with prominent BR about one third from the other end.
vitA1:
vitB1:    Puff (gp. 7) about one third from distal end of the arm with dark bands distal.
vitC1:
vitD1:
vitE1:
vitF1:
vitG1:    Nucleolus subterminal,BR about one third from other end; closely paired.

[ Return to Index | Go to C. vitellinus adult ]
Modified: 6 April 2023
Access: Unrestricted
Copyright © 2020-2023, Jon Martin.