9. Chironomus n.sp. NZ9


Adults and Pupa not known

Larval Morphology: salinarius type larva, length 15.5-15.9 mm (female), 12.5-15.7 mm (male).    Head capsule with gular region darkened, frontoclypeus very slightly to slightly darkened, but with some darkening of the posterior border.
Mentum with 4th laterals slightly reduced, but may still be above level of 5th laterals (essentially type II); c1 tooth characteristically broad and flat on top, c2 teeth relatively well separated; 6th lateral arising at a slightly lower level than other teeth.
Ventromentum with about 36-40 striae.  Pecten epipharyngis with about 14-15 relatively even teeth.
Antenna with basal segment about 3.25x longer than wide, RO about a third up from base; AR 1.92-3.10, fourth segment about 1.6x length of 3rd; antennal proportions (micron) 141 : 35 : 10 : 15 : 8.
Mandible of type II, with about 18 - 22 grooves on outer surface near the base; Pecten mandibularis of 10-14 bristles.
Gut of most larvae almost filled with sand particles.

Cytology: 4 polytene chromosomes with thummi cytocomplex arm combination (AB, CD, EF, G).
    Centromeres heterochromatic.  Two nucleoli, one proximal in arm F; the other about one third from the heterochromatic end of arm G.  A Balbiani ring developed near distal end of arm G.  Arm A with the sequence A4 found in Australian species; arm E with sequence E1 of the Australian species; and arm F as in C. oppositus F3 and C. australis..  No polymorphism in the small sample examined.

Arm A1:    1a-e, 11-10, 2c-1f, 3e-2d, 8-9, 3f-i, 12c-a, 4-7, 13-19                ie. as A4 oppositus
Arm B1:    Puff (group 7) and about 2 distal dark bands (8ab) , close to 4 characteristic bands.
Arm C1:    possibly 10A-10D6, 11B11-10D7, 11B12-11E;     ie. as C2 of forsythi
Arm D1:    1 - 2, 16c-a,17e-a, 10c-a, 3e - 9, 3d-a, 10d -15, 18 - 24                ie. as forD1, nzlD2
Arm E1:    1 - 3e, 10b - 3f, 10c - 13                            ie. as E1 oppositus, analis
Arm F1:    1 - 2a, 10 - 2c, 15c - 11a, 2b, 15d - 23            ie. as F3 of oppositus, and F1 of australis and forsythi
Arm G1:

North Island:
    Lake Okaro, Rotorua area (NZ.10.8 & NZ.10.9) (D.J.Forsyth & S. Ibarrarán) 14-ix-1982 and 14-ii-2007
    Lake Okareka, Rotorua area (S. Ibarraran) 15-ii-2007
South Island:
    Lake Hayes, c.13 km n.e. Queenstown, Westland (NZ.47.1) (Jon Martin) 7-i-1974

MtCOI sequence suggests that there may be hybridization with C. “castaneum” particularly where they occur together in the same lake.  On the other hand, there is a possibility that this is a unique whole-arm translocation event with no connection to other species in the thummi-cytocomplex.  At such, this species would be immediately reproductively isolated from its pseudothummi-cytocomplex parent.  The limited mitochondrial DNA difference would then reflect that this event occurred relatively recently.

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Modified: 2 September 2020
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