AUSTRALIAN CHIRONOMUS SPECIES

Compiled by Jon Martin
Genetics, Genomics & Development, Schhool of Biosciences, The University of Melbourne, Victoria, 3010, Australia


When Freeman (1961) revised the Australian Chironomidae he recognized six species of the genus Chironomus (s.s.): C. alternans Kieffer, C. australis Skuse, C. nepeanensis Skuse, C. tepperi Skuse and C. vitellinus Skuse.  However, even at that stage it was known that adults of C. alternans could be produced from distinct larval types, and with quite distinct polytene chromosomes, which appeared to be distinct species.  Bugledich et al. (1999) 'Family Chironomidae' from Zoological Catalogue of Australia, recognize 12 species of Chironomus in Australia, with another nine species that are Incertae cedis.  Only two of these latter nine, which are currently nomena nuda, are considered here.
There is also one species of Einfeldia in Australia, E. australiensis (Freeman) which Freeman placed in Chironomus (Xenochironomus).  This species is included here as the relationship of Einfeldia to Chironomus has been subject to much discussion.

This listing is also available in pdf format (6.2 MB)(Updated 7 January 2014).


In general, the morphological terminology used in this document follows Sæther (1980), Webb & Scholl (1985) and Vallenduuk & Moller Pillot (1997).



1. Adult morphology

Species with an Australia-wide distribution
Chironomus cloacalis Martin, 1971
Chironomus 'februarius' - currently nomen nudum, but described in Martin 1966
Chironomus nepeanensis Skuse, 1889
Chironomus 'pseudoppositus' - currently nomen nudum, but described in Martin 1966
Chironomus tepperi Skuse, 1889

Species with a tropical distribution
Chironomus bicoloris Tokunaga, 1964
Chironomus circumdatus (Kieffer, 1916)
Chironomus javanus Kieffer, 1924
Chironomus pallidinubeculosus Tokunaga, 1964
Chironomus magnivalva Kieffer, 1917
Chironomus 'queenslandicus' - manuscript name
Chironomus sp. (bathophilus type)
Chironomus nr. samoensis

Species with a south eastern distribution
Chironomus australis McQuart, 1847
Chironomus duplex Skuse, 1889
Chironomus 'jacksoni' - manuscript name
Chironomus maddeni Martin & Cranston
Chironomus oppositus Skuse, 1889:
form connori
form oppositus
form whitei
Chironomus 'timmsi' - manuscript name
Chironomus 'tyleri' - manuscript name (formerly C. oppositus f. tyleri)
Einfeldia australiensis

Species with a western distribution
Chironomus occidentalis Skuse, 1889
C. oppositus f. edwardi

Species from Norfolk Island
Chironomus 'februarius' (?)
Chironomus species NI 1 (may be as Chironomus nr. samoensis)
Chironomus species NI 2

The description of Chironomus alternans Walker and the synonyms listed by Freeman (1961) are also included, although they are considered as uncertain.  Further description is provided for those where the types are still available:

C. alternans

C. januarius

C. subdolus



In the adult descriptions reference is made to the types of superior volsella shape as recognized by Strenzke (1959).  This is a helpful initial classification, but experience has shown that the types are not discrete, but are part of a continuum.    The three categories as described by Strenzke are:
S-type: The SV is shoe shaped, i.e. it is drawn out distal-medially into a broad, rounded lobe (Fig. a-c, below) (Strenzke's figure suggests the most distal point will be at the toe of the shoe).
D-type: The SV is ribbon-like: distally it may have a weakly thickened shoulder (Fig. d, below) (most distal point is not at the internal margin), or bent in a shallow sickle-shape (Fig. e-f, below).
E-type: The SV has the form of an elephant's tusk; distally it is sharply graded to a point, or with an expanded knob (Fig. g-i, below) (line from base to most distal point goes outside the limits of the SV).

Key to Adults

1a Anal point stout 2a
1b Anal point longer or tubular 3a
     
2a(1a) Anal point bulky and strongly turned down, abdomen greenish Einfeldia australiensis
2b Anal point not bulky or strongly turned down, abdomen dark C. 'queenslandicus'
     
3a(1b) Wing with dark spot over cross vein and with fuscous clouds, particularly in cell R5 C. pallidinubeculosus
3b Wing with at most darkening of cross vein 4a
     
4a(3b) Cross vein strongly darkened, LR about 1.5, wing length 4-5 mm Chironomus nepeanensis
4b Cross vein not strongly darkened 5a
     
5a(4b) Legs shorter than usual, posterior LR about 0.5; male hypopygium enlarged, anal point deep and laterally flanged 6a
5b Posterior LR about 0.7 or higher; male hypopygium of normal type 7a
     
6a(5a) Thorax dull grey, pits of dorsocentral setae very distinct; inferior volsella of male very swollen Chironomus tepperi
6b Thorax greenish with brown stripes, pits normal; inferior volsella of male not swollen Chironomus magnivalva
     
7a(5b) Wing length greater than 5 mm; anterior tarsi of males bearded 8a
7b Wing length less than 5 mm; anterior tarsi of males bearded or unbearded 10a
     
8a(7a) Distributed on east of the continent, including Tasmania 9a
8b Distributed on the west of the continent, including Northern Territory Chironomus occidentalis
     
9a(8a) Mid femur more than 1.12 x the anterior femur (likely to be) Chironomus duplex
9b Mid femur shorter than the anterior femur (likely to be) Chironomus australis
     
10a(7b) Blackish species.  Male with bearded anterior tarsi and spatulate superior volsella Chironomus 'timmsi'
10b Paler species, at most brown.  Male tarsi not bearded 11a
     
11a(10b) Thorax pale, anterior femur and tibia pale, tarsi with dark pattern 12a
11b Thorax pale to brown, legs unbanded (mainly members of the 'C. alternans' group) 13a
     
12a(11a) Tarsi darkened at both apex and base, anal point tubular Chironomus javanus
12b Tarsi darkened only at distal ends, anal point larger and narrowed at base, LR above 1.80, anterior tarsus 5 at least 0.35 times the length of the tibia, SV often beaked Chironomus nr. samoensis
     
13a(11b) Wing length over 4 mm.  Chironomus 'tyleri' (AR 2.9-3.2), abdomen greenish with narrow saddle markings, extending in length from 5th tergite to occupy most of segment by 8th tergite; Chironomus cloacalis in part.(AR 3.3-4.25), abdominal tergites generally dark with pale posterior band, but may have saddle spots.

          Wing length less than 4 mm.
Chironomus cloacalis mostly (AR 3.3-4.25), etc.; C. oppositus (type AR 3.6); C. maddeni (AR 2.5-2.9); C. 'jacksoni' (AR 2.4-3)

Chironomus 'februarius' (Abdominal tergites may be as C. cloacalis, or may have dark band across the centre of the segment; AR 2.9 - 3.4; LR 1.56 - 1.65.), Chironomus 'pseudoppositus' (Abdominal tergites as in C. cloacalis AR 2.5 - 3.1; LR 1.5 - 1.8; superior volsella less curved than in other members of the oppositus-group)
Abdomenal tergites with saddle spots: Chironomus oppositus (LR 1.5 - 1.8; wing length 2.8 - 3.6, Chironomus maddeni (AR 2.55 - 2.86; LR 1.6 - 1.8; wing length 2.4 - 3.36 mm), Chironomus 'jacksoni' (AR 2.4 - 3; LR ); Chironomus 'tyleri' (AR 2.9 - 3.2; LR 1.53 - 1.66; wing length 4.3 - 4.5 mm).
- need to be inserted at 8.
Norfolk Island species: Species 1 may be near C. samoensis, superior volsella closest to Strenzke's type D(d), LR about 1.54 (i.e. lower than C. nr. samoensis, but in range of C. samoensis itself).
Species 2 has an superior volsella that is closest to Strenke's type D(f), but appears to have a flattened end. LR about 1.27.

2. Larval types and Karyotypes

In the following descriptions, reference is made to the mentum and mandible types originally devised by Webb & Scholl (1985), Vallenduuk & Moller Pillot (1997), and Proulx et al. (2013).  These classifications were made for relatively small numbers of species, but with the much larger number of species, such as in the North American fauna, they do not cover all the variability seen in these characters and so further modification has been necessary.

The MENTUM TYPE is defined only by the degree of development of the 4th lateral teeth:


Type I - height in same line as the rest of the lateral teeth;
Type II - 4th laterals reduced, height about equal to that of the 5th laterals;
Type III - 4th laterals further reduced, height less than that of the 5th laterals.


The mentum may be further classified by the characters of the CENTRAL TRIFID TOOTH:
Type IA - c2 teeth only partially separate from c1, i.e. as shoulders on c1 (figure a).
Type IB - c2 teeth slightly more separated (figure b).
Type IIA - c1 broad, c2 teeth distinctly separated (figure c).
Type IIB - c1 very broad, c2 less separated (figure d).
Type III - c1 tooth relatively narrow and much higher than the separated c2 teeth (figs e and f).
Type IV - c2 teeth well separated, not much lower than the relatively narrow c1 tooth (figs g and h).




The MANDIBLE TYPE is defined by the degree of darkening and separation of the 3rd inner tooth:
It seems better to consider the two characters separately.

This figure shows IA; IIB; IIIC respectively

Separation:
Type I - tooth fused
Type II - tooth partially free
Type III - tooth completely separated
Color:
Type A - tooth pale
Type B - some degree of pigmentation
Type C - as dark as other inner teeth

VENTROMENTAL PLATE RATIO - ratio of the width of the marginal region of ventromentum (usually seen as a granular band under light microscopy) (a in figure below) to the distance from the anterior margin to the base of the striae (b in figure below).


VMR = a/b

PECTEN EPIPHARYNGIS -
Proulx et al. (2013) recognised 4 types of PE in North American species.  These are useful if the teeth are not worn down, as they often are in older larvae.  Type D does not occur in any known Australian species.

Type A - fine sharp rather uniform teeth.



Type B - teeth broader but still sharp.  Sometimes with one or two fine smaller teeth interspersed.


Type C - rounded and rather uniform.  Worn type B teeth may be mistaken for this type.


Type D - rounded teeth with smaller teeth interspersed (generally found in the subgenera Lobochironomus or Chaetolabis which have not been found in Australia).

Larval types referred to in Key and in descriptions are defined here.

Provisional Key to 4th Instar Larvae

1a Larger larvae, length up to about 23 mm.  (Either thick bathophilus-type larvae with large, very darkly pigmented heads, or a slim plumosus-type larva with a small, pale head capsule) 2a
1b Medium sized larvae, length up to about 19 mm, head length less than 400 mm. 5a
     
2a(1a) Head capsule heavily darkened, bathophilus-type 3a
2b Head capsule pale, except NT and Vic where slight darkening of the gula & frontoclypeus occurs, slender plumosus-type C. nepeanensis.
     
3a(2a) Distributed on east side of the continent only (NSW, VIC, SA, TAS) 4a
3b Distributed on west of continent only (WA & perhaps NT) C. occidentalis
     
4a(3a) Teeth of mentum rounded (when not worn), c2 teeth of centre trifid tooth only partially distinct from c1 tooth (type IIa).  Four polytene chromosomes C. australis
4b Teeth of mentum square sided and pointed, c2 teeth well separated from c1 tooth.  Three polytene chromosomes, inversion polymorphism C. duplex
     
5a(1b) Larvae with lateral tubules (species often polymorphic) 6a
5b Larvae without lateral tubules (species often polymorphic) 12a
     
6a(5a) Larvae of the true plumosus type (posterior ventral tubules coiled) 7a
6b Larvae of the melanotus- or semireductus- type (posterior ventral tubules may be bent) 16a
     
7a(5a) Head capsule generally quite heavily darkened on both frontoclypeus & gula 8a
7b Head capsule darkened on gular region only 10a
     
8a(7a) Both gula and frontoclypeus quite heavily darkened C. cloacalis (majority)
8b Gula and frontoclypeus slightly to moderately darkened, tropical species 9a
     
9a(8b) c2 teeth of mentum sharp and well separated (type III), 3rd inner tooth of mandible type IA/B C. nr. samoensis
9b c2 teeth of mentum only partially separated (type IB), 3rd inner tooth of mandible type IIIB C. magnivalva
     
10a(7b) Lateral tubules tending to be more ventrally placed, premandible with 7 teeth C. javanus
10b Larvae not as above, premandible with the normal 2 teeth 11a
     
11a(10b) Head capsule often completely pale, but sometimes slightly darkened at posterior of gula, basal segment of antenna less than 4 times as long as wide C. pallidinubeculosus
11b Basal segment of antenna more than 4 times as long as wide: 12a
     
12a(11b) Larvae of the halophilus-type (i.e. VT reduced, often only the posterior pair ), hind prolegs sharply narrowing C. tepperi (part)
12b Larvae with VT of long or moderate length 13a
     
13a(12b) Larvae of the plumosus-type 14a
13b Larvae of the bathophilus-type ??
     
14a(13b) Gula darkened at least on posterior half 15a
14b Gula pale or only slightly darkened on posterior third 17a
     
15a(14a) Gula dark, centre tooth of mentum of type III C. circumdatus
15b Gula moderately darkened, centre tooth of type IB pale headed form of C. cloacalis
     
16a(6b) Lateral tubule over 200 micron; antennal ratio A2/A1 more than 0.3; inner margins of ventromental plates separated by only about 0.2 of mentum width C. 'queenslandicus'
16b Lateral tubules less than 200 micron; antennal ratio A2/A1 less than 0.3 C. oppositus forms oppositus, and whitei; C. 'tyleri'; and C. 'edwardi'.
     
17a(14b) Mentum of type II; Central trifid tooth type III C. 'februarius'
17b Mentum of type I; Central trifid tooth type III C. bicoloris

    18.   Basal segment of antenna 3 to 3.5 times as long as wide; four polytene chromosomes . .C. 'timmsi'            Basal segment of antenna about 4 times as long as wide; three polytene chromosomes. . . . . . . . . . . . . . . . . . . . C. sp. Bakers Beach
            (some specimens of C. tepperi may key to here if they have relatively well developed ventral
            tubules. They have a sharply narrowing hind proleg; basal segment of antenna up 5 times as long as
            wide; and four polytene chromosomes)

   19.    Antennal ratio A2/A1 more than 0.3, A4 hardly longer than A3 . . . . . . . . . . C. sp. (bathophilus-type)
            Antennal ratio A2/A1 less than 0.3
          C. oppositus forms;    C. 'pseudoppositus';    C. maddeni;    C. 'jacksoni'.


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