Larval types and Karyotypes, with Adults where data available

Integration of data of Jon Martin1 and Don Forsyth>
1 Genetics, Genomics & Development, School of Biosciences, University of Melbourne, Victoria, 3010, Australia
2 Deceased

When Freeman (1959) revised the New Zealand Chironomidae he recognized two species of the genus Chironomus (s.s.): C. zealandicus and C. analis. However, even at this stage it was known that adults of C. zealandicus could be produced from two distinct larval types, a salinarius-type (lacking ventral tubules) or a so-called "thummi-type" (with ventral tubules)(Forsyth, 1971), although in fact the latter are a bathophilus-type.  (The current classification system can be found here.)

Analysis of the polytene chromosomes further indicated that there were different chromosome number forms of both the salinarius- and the thummi-type larvae ( Lentzios et al. 1980), which appeared to be distinct species.  With the integration of the morphological and ecological analyses of Don Forsyth, the karyotypic studies of Jon Martin, and DNA studies with Ian Hogg and Sofia Ibarrarán, we have concluded that there are at least fourteen species of Chironomus in New Zealand.  (Note that this only includes one of the two species described by Sublette & Wirth (1980) from the subantarctic islands), and includes an Australian species that may be a recent migrant.  DNA studies are suggesting some of these are groups of closely related species as is common in other parts of the world.  Where possible a link to the relevant Bin in the BOLD Database ( is given.
Seven of the currently recognised species have a salinarius-type larva, and seven others are bathophilus-type, although one is polymorphic for ventral tubule development, some having only slight development of the posterior pair of ventral tubules (halophilus-type).  The larva of the fifteenth species is unknown.

This listing is also available in pdf format (7 MB)(Updated 30 November 2022).

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

Provisional Key to Adult Males
(based on data of D.J. Forsyth)

1a Anal point stout C. analis
1b Anal point narrower 2a
2a(1b) Abdominal tergites with dark saddle spots 5a
2b Abdominal tergites with bands or patches covering most of the segment 3a
3a(2b) Anterior tergites with a band over only about two thirds of the segment 4a
3b Anterior tergites with band over most of the segment C. 'thermarum'
4a(3a) Pigmentation of the anterior tergites narrowing to the posterior edge C. 'castaneum' (North Island)
4b Pigmentation of anterior segments covering whole width of segment 7a
5a(2a) Anterior LR generally above 1.5; only short sparse beard C. forsythi (part)
5b Anterior LR below 1.5; may or may not have beard 6a
6a(5b) Lacking a beard C. 'campano'
6b Dense short beard and sparse long beard C. zealandicus
7a(4b) Anterior LR generally above 1.5; only short sparse beard (BR <3) C. forsythi (part)
7b Anterior LR probably just below 1.5, at least some longer beard (BR 3-7) 8a
  note: *C. nr. antipodensis would also fit here, but LR not known
8a(7b) Dense short beard and sparse longer beard (BR 4-7) C. novaezelandiae
8b Moderate beard (BR 3-4) (based on only 1 specimen) C. sp. NZ12

Note that the adults of some species are unknown.
The adults of C. 'spilleri', and C.sp. NZ12 are assumed to be similar to those of
C. novae-zelandiae since Don Forsyth included them all under that name.
The Australian species C. 'pseudoppositus' has been recognized in New Zealand on the basis of mtCOI sequence, but the morphology has not been compared with that of Australian specimens.

SV typeIn 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).

Provisional Key to Fourth Instar Larvae

1a Larva a salinarius-type 2a
1b Larva with at least some development of ventral tubules 8a
2a(1a) More than 60 striations on Ventromental plate C. zealandicus (= C. species a)
2b Less than 60 striations on Ventromental plate 3a
3a(2b) Anal tubules relatively long sometimes with slight constriction near middle C. forsythi in part
3b Anal tubules relatively short, pointed or rounded 4a
4a(3b) Frontoclypeal region of head pale or only slightly darkened 5a
4b Frontoclypeal region very dark 6a
5a(2a) c1 tooth of mentum broad (IIA) and flattened sp. NZ9
5b c1 tooth of mentum narrower (type IIA) and more pointed C. 'thermarum'
6a(4b) c1 tooth of mentum broad (type IIA) 7a
6b c1 tooth of mentum generally narrower.(usually type 3) C. analis
7a(6a) Mandible of ty. IIB or C (occasionally IIIC), with about 15- 25 furrows C. 'castaneum' and C. 'campano'
7b Mandible of ty. III, with about 26 furrowsC sp. NZ14
8a(1b) Slight development of posterior ventral tubules only C. 'thermarum' (in part)
8b Two pairs of ventral tubules present 9a
  note: for 8a, in thermal waters (but C. zealandicus, species 10 and sp. 12 can be also)  
9a(8b) Anal tubules relatively long, as in C. forsythi 10a
9b Anal tubules shorter and rounded 11(a)
10a(9a) Anal tubules all about equal and 2.5x longer than wide (3 polytene chromosomes) sp. NZ8C. sp. NZ8
10b Anal tubules about 2.5-4.2 times longer than wide, dorsal pair often longer. C. 'pseudoppositus'
11a(9b) Head somewhat narrower, ratio mentum width/VHL less than 0.65, ventral tubules sometimes longer than 1.0 mm. C. novaezelandiae group
  Note: Frontoclypeus generally darkened but sometimes pale or only slightly darkened (which group would include C. "spilleri"; and C. sp. NZ12).  Variability possibly reflecting presence of more than one species.  
11b Head broader, ratio mentum/VHL above 0.65; with darkened frontoclypeus, ventral tubules about 0.5-1.0 mm. C. sp. NZ7
  Note: not in North Island  

Reference is also made to the mentum and mandible types originally devised by Webb & Scholl (1985) and Vallenduuk & Moller Pillot (1997) and Proulx et al. (2013), as well as a ventromental plate character.  The previous classifications were made for relatively small numbers of species, but 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).
In NZ there are are 2 forms of type IIA: the usual form, here called 'IIA narrow' and 'IIA broad'

Ventromental plate ratio (VMR) - 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).

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).

Premandible -
Assessment of the premandible can be difficult due to quite excessive wear and distortion in mounting. Where they are in good condition and lying flat, they can be categorised into 5 groups based on the relative widths of the teeth and whether they come to a sharp or a broad point. The teeth are measured as close as possible to their bases.
Premandible types
Type A: Both teeth narrow and coming to a fine point.
Type B: inner tooth moderately broad, about 3-5 times wider than, outer tooth. This can be split into 2 subgroups:
B1 both teeth come to relatively fine points.
B2 the inner tooth comes to a relatively broad point.
Type C: Both teeth are moderately broad, coming to relatively broad points.
Type D: Inner tooth very broad, outer tooth moderately broad.
Type E: Both teeth very broad and often quite short.
C. vitellinus has a six toothed premandible (C. javanus has five teeth).
Species of Kiefferulus also have a five-toothed premandible, but it is broader.

Antennal ratio (AR) - measured on only the length of the sclerotized region of the segments, since the unsclerotized regions can expand to different extents in different specimens. Measured in this way the AR is usually higher.

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

This figure shows IA; IIB; IIIC respectively

New Zealand has strong ties to the islands of the Pacific Ocean.  This makes this listing a convenient place to record Chironomus species from these islands, although there appears to be no overlap of the Chironomid fauna (rather, many of them in fact are also found in South East Asia, so are also recorded in the listing of those species)

Chironomus bicoloris Tokunaga 1964

Chironomus carolinense Tokunaga 1964

Chironomus circumdatus (Kieffer, 1916, as Tendipes)

Chironomus claggi Tokunaga 1964

Chironomus crassicaudus Tokunaga 1964

Chironomus hawaiiensis Grimshaw 1901

Chironomus magnivalva Kieffer, 1917

Chironomus nigerilateralis Tokunaga 1964

Chironomus pallidinubeculosis Tokunaga 1964

Chironomus preapicalis Tokunaga 1964

Chironomus samoensis Edwards 1928

Chironomus sexipunctatus Tokunaga 1964

Chironomus trifasciatus Tokunaga 1964

Chironomus vitellinus Freeman 1961

Chironomus "harrisi" (sp. Fiji1)

Chironomus zealandicus Hudson, 1892

There have been several attempts to relate C. zealandicus to one of the cytologically known species, and it has been suggested at different times that it was either species 1 (Forsyth, 1978 and Martin, 1998) or C. species a (Martin, 1996).
However, species 1 can be ruled out because there is an entry in Hudson's journal that he reared the specimens of C. zealandicus from larvae without ventral tubules.  Forsyth therefore thinks that C. species a is the species that corresponds to Hudson's C. zealandicus.  This is supported further by the fact that C. species a is the largest of the reared species, about the size of Hudson's C. zealandicus specimens.
The name is therefore used in this sense in this work.

Chromosome banding patterns have been published using the Australian standard system of Martin (1964), but are in process of being switched to the more universally used (although more difficult to uniquely specify bands) system of Keyl (1962) and Devai et al. (1989).

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