Chironomus quinnitukqut, Martin, Jon, Sublette, James E. & Caldwell, Broughton A., 2010

Martin, Jon, Sublette, James E. & Caldwell, Broughton A., 2010, Description of Chironomus quinnitukut, n. sp., closely related to the C. decorus group in North America, with characterization of an additional larval form from halobiontic habitats, Zootaxa 2716, pp. 29-41 : 30-38

publication ID	https://doi.org/ 10.5281/zenodo.199718
DOI	https://doi.org/10.5281/zenodo.6204736
persistent identifier	https://treatment.plazi.org/id/70432353-D325-BE1F-FF69-1428122D69B3
treatment provided by	Plazi
scientific name	Chironomus quinnitukqut
status	sp. nov.

Treatment

Chironomus quinnitukqut View in CoL n. sp.

Chironomus halophilus Packard 1874: 245 View in CoL & 415: nomen dubium. The description is inadequate for recognition other than generic placement as a Chironomus View in CoL and is listed here to avoid future possible confusion.

Chironomus atrella (Townes) Anderson and Hitchcock 1968: 1597 View in CoL : (misidentification).

Chironomus atrella (Townes) Hitchcock and Anderson 1968: 16 View in CoL : (misidentification).

Chironomus View in CoL species 2n Martin 2010: karyotype and associated larva.

Type material. Holotype, male: U.S.A., Old Saybrook, CT, light trap, 10-VI-1966, SWH, in UMN. Allotype female, Paratypes 59 male, 22 female, Old Saybrook, CT, light trap, 10-VI-1966, 33 sgcl, South Cove, 17-V- 1966, SWH.; 14 sgcl., Old Saybrook, CT, (approx 21 ppt salinity), 28-VIII-1970, JM and SWH, UCT 2-1, in UMN and ZSM; 3 sgcl., Truro, Barnstable Co., MA, Pilgram Lake, East Harbor, Cape Cod National Seashore, (19 ppt salinity), 29-VII-2005, JP.

Etymology. A common transliteration of the Mohegan (Algonquin) word meaning “place of long tidal river”, referring to the Connecticut River, the longest in New England and the source of the state name, Connecticut. The marsh, which is the type locality, at South Cove, Old Saybrook, near the Connecticut River mouth, has been designated as “Wetland of international importance”. To be used as a noun in apposition.

Diagnostic characters. This species will key in Townes (1945, P.117) to couplet 18 containing C. atrella ; however, it does not fit the description of C. atrella as this species has a lower foreleg ratio and distinctive differences in the structure of its genital apparatus. The remaining three species in the key (couplets 19 and 20) all have broad anal points or other differences. The most distinctive features, a very narrow base to the anal point and an elongate, slightly curved superior volsella with an upturned tip, clearly separate C. quinnitukqut n.sp. from all other members of the genus in North America. The few other species with a narrow anal point have differently shaped anal points and superior volsellae. One specimen before us may represent a new species; perhaps C. sp. Cape Cod; it differs slightly in genitalia, coloration, some meristics, and size, being larger. Unfortunately, its foretarsi are missing and its association with sp. Cape Cod is not certain; thus it is not described further or included in this species account. A second specimen may also belong to this variant and is also excluded due to lacking foretarsi. The only known pupal spur, with three spines, has more than that of C. atrella , which has only one or two.

Larvae can be differentiated from C. atrella by the larval type ( Shobanov et al. 1996), which is bathophilus in C. quinnitukqut and plumosus in C. atrella . At Cape Cod it was found with C. species 'Cape Cod’ (sp. 4k of Martin 2010), which is also a bathophilus-type larva with a similar VHL, but is sometimes distinguishable by the lower number of teeth in the pecten epipharyngis and the greater reduction of the fourth lateral teeth of the mentum.

Cytologically the fixed pericentric inversion in the CD chromosome is diagnostic; the median position of band groups 24–28 in arm B will distinguish it from all species other than sp. Cape Cod, where the sequence appears similar, and C. decorus Johannsen in which these bands are in the reverse orientation. The relatively longer arm G will distinguish it from C. atrella , and the lack of a distinct heterochromatic band adjacent to the nucleolus, along with pairing usually only at the distal end of arm G will distinguish it from sp. Cape Cod.

Description. Male imago. Holotype male.

Coloration: Thoracic vittae, postnotum, a spot on the pleural sclerites, pre-episternum, a spot posterior to the lateral vittae, legs and abdomen largely blackish; ground color of head, thorax, including most of antepronotum and scutellum and narrow apices of the abdominal tergites paler yellowish.

Head: Antennal ratio 3.57 [3.41–4.70, 4.16 (8)]; temporal setae 35 [22–35; 30 (10)]; clypeal setae 38 [24– 56; 36 (10); ocular ratio 0.20 [0.17–0.19; 19 (4)]; frontal tubercle length 30 [25–42; 33 µm (9), almost as wide as high]; clypeal width/pedicel width 1.0 [0.7–0.86; 0.78 (7)]; palpal proportions (apical four flagellomeres): 70:203:189:224µm.

Thorax: Antepronotum rather narrow, slightly projecting at the apex. Dorsocentral setae 29 [25–42, 31(10)], in a single to mostly triple row; acrostichal setae present but obscured in lateral mount; prealar setae 7 [6–7, 7 (9)]; scutellar setae 26 [22–42, 29(10)], mostly in a single slightly staggered row laterally, becoming doubled at medial apex.

Wing: Anterior veins darkened with r-m slightly darker still; R2+3 ends at 0.33 of the distance between R1 and R4+5; wing length 3.70 mm [2.96–4.31, 3.57 (10)]; setae: R 24 [24–45; 27 (5)]; R1 8 [6–19; 16 (5); R4+5 7 [3–7; 6 (5)]; squamal 36 [21–43; 30 (9)].

Legs: Ratios p1 1.16 [1.14–1.22; 1.17 (6)]; p2 0.58 [0.55– 0.59; 0.57 (6); p3 0.71 [0.70– 0.75; 0.72 (5)]. Beard ratio, p1 4.15 [5.71–7.16; 6.33 (6)]. Sch, p2 9 [12–21; 15 (7); p3 13 [9–19; 14 (7)].

Genitalia: ( Fig. 1 View FIGURE 1 ); gonostylus width/length ratio 0.22 [0.19–0.21; 0.20 (5)]; gonostylus/gonocoxite ratio 0.73 [1.11–1.37; 1.18 (5)]; superior volsella of the E-type ( Strenzke 1959), length 150 [112–165; 145 µm(9)]; inferior volsella length 220 [185–234; 209 µm (9)]; Inferior volsella setae 37 [31–46; 38 (9)]; TIX setae 2 [2– 7; 5 (9)].

Female imago. Allotype female.

Coloration: Similar to male but with the paler abdominal incisures slightly more pronounced.

Head: Antennal proportions 150:85:85:105:270 µm; palpal proportions 75:210:190:240 µm; temporal setae 19; frontal tubercles about as wide as high; clypeal setae 38; ocular ratio 0.18.

Thorax: Coloration as holotype male. Antepronotum similar to holotype male; setae: dorsocentral 41 extending anteriorly to near antepronotum; acrostichal present but not counted; prealar 7; scutellar 38.

Wing: Veins coloured as male but more intensely; R2+3 somewhat folded under, ending at 0.17 of distance between R1 and R4+5; wing length 3.61mm; setae: R 30: R1

28; R4+5 39; squamal 38; VR 1.12.

Legs: p1 LR 1.24; p2 LR 0.55; p3 LR 0.71; Sch p2 47; p3 54.

Genitalia: Fig. 2 View FIGURE 2 .

Pupa. No pupae were available, but the following pupal characters were determined from a late prepupa: Basal Ring about 140 µm long, but folded over obscuring width, setal fringe of anal lobe multi-layered, about 115 setae on each side, spur of segment VIII ( Fig. 3 View FIGURE 3 g) about 250 µm long, with 3 spines progressively along the outer edge.

Larva ( Fig. 3 View FIGURE 3 ). A medium sized bathophilus– type, length about 11.2–13.2 (6) mm, VHL about 300µm [278–311 µm (11)], lateral tubules absent. Ventral tubules relatively short, but length may be influenced by ecological factors since those of larvae from Old Saybrook are much shorter than those from Truro [anterior about 0.38–0.46 mm (4) and 0.75–1.04 mm (3) resp., posterior about 0.28–0.46 mm (4) and 0.96 mm (2) resp]. Gular region dark to very dark over most of its surface, frontoclypeus pale, but sometimes with slightly dark lines alongside it and some darkening around the base of the antenna. Setae of labrum typical for the genus. Mentum ( Fig. 3 View FIGURE 3 d) with somewhat rounded teeth; c1 tooth broad and relatively tall, c2 teeth little more than notches (type I–II); fourth laterals slightly reduced compared to the third and fifth laterals, sixth laterals often arising lower than the line of origin of the other laterals. Ventromental plates ( Fig. 3 View FIGURE 3 e) with about 38 – 46 (11) striae, and separated from each other by about a third [0.29–0.37 (11)] of the total width of the mentum. Premandible ( Fig. 3 View FIGURE 3 b) with inner tooth 2–3 times wider than outer tooth. Pecten epipharyngis ( Fig. 3 View FIGURE 3 a) with about 13–20, 15 (11) irregular teeth. Mandible ( Fig. 3 View FIGURE 3 f) with third inner tooth relatively well developed and almost completely separated (type II–III), with about 12–16 striae on the inner surface near the base. Antenna ( Fig. 3 View FIGURE 3 c) relatively short, basal segment only about 0.4 times the VHL [0.39–0.44 (11)] and about 2.3–3.2, 2.9 (11) times longer than wide, ring organ a third to half way up the segment; antennal ratio 1.99–2.33, 2.13 (11); antennal segments (µm): 123:24:7:13:7. Anal tubules short and rounded, about 230–555 (12) µm long, generally less than twice as long as wide [1.2–2.4x, 1.5x (12)].

Karyotype ( Fig. 4 View FIGURE 4 ). Four polytene chromosomes in salivary gland cells, with the chromosome arm combination AB, CD, EF, G (thummi-cytocomplex). Keyl pattern difficult to recognise, particularly for chromosome AB where the characteristic bands (groups 24 to 27) of arm B are away from the centromere and the “olive” (groups 6 and 7) of arm A is not obvious. In the CD chromosome, arm D is relatively shorter than arm C, as the result of a fixed asymmetrical pericentric inversion which moves band groups D24 to 21 into arm C, while only group C22 is added to arm D. The main nucleolus is virtually terminal in arm G, but a second nucleolus may be developed immediately distal to the four characteristic bands of arm B. Arm G may be fully paired, but is usually unpaired towards the nucleolus. Only one Balbiani Ring (BR) is normally visible in arm G, about one third of the distance distal from the nucleolus, but another may be developed near the distal end. Inversion polymorphism has been observed in all arms except for arm B.

Arm A. The banding pattern is difficult to identify, but there are some points of similarity to sequences in two other members of the decorus -group, C. decorus itself (sp. 3a of Martin et al. 1979) and C. decorus -group species 2 ( Butler et al. 1995). The distal bands of qutA2 appear similar to those in the equivalent position of decA1 ( Fig. 5 View FIGURE 5 a, b)., while the proximal bands labelled ‘a’ in Fig. 4 View FIGURE 4 , appear similar to the proximal bands of C. decorus -gp sp. 2. Sequence A2 is derived from A1 by a simple inversion of about half of the arm ( Fig. 5 View FIGURE 5 b,c)

Arm B. As noted above, the characteristic bands, about 23a to 28e, are located away from the centromere by about one third of the length of the arm. These bands are reversed (28e - 23a) compared to the normal pattern (23a - 28e) in other species ( Fig. 4 View FIGURE 4 ), sometimes with a nucleolus developed at their distal limit (about group 28) ( Fig. 5 View FIGURE 5 b). This nucleolus was observed in a single specimen from Connecticut ( Fig 5 View FIGURE 5 c). It appears that group 7 is towards the distal end of the arm ( Fig. 5 View FIGURE 5 b), although the puff often developed in this group in other species, is rarely developed.

Arm C. As noted above band group C21 is followed by groups D21–24. The banding pattern from 1–12c may correspond to that of bla2 of C. blaylocki ( Wuelker et al. 2009) , with the typical constriction of groups 4- 3 within this region ( Fig. 4 View FIGURE 4 ), although the sequence between 2e and 4 is not clear. The polymorphism in C is a small inversion within this region ( Fig. 6 View FIGURE 6 a), perhaps 2d-5, found only as occasional heterozygotes. The rest of the banding pattern up to the inserted regions of arm D is uncertain.

qutC1: 1 - 2e, 12b?, 6b? - 2f, 12c,? -?, 21, (D)21 - 24

Arm D. There are two sequences of this arm. The inversion covers about one third of the arm, starting over one third from the distal end of the arm, and appearing to extend almost to the centromere due to lack of pairing ( Fig. 6 View FIGURE 6 ), although the inversion is actually shorter ( Fig. 4 View FIGURE 4 ). The banding sequence is uncertain, but it is likely that the groups 19 and 20 are immediately distal to the inverted group 22 from arm C.

Arm E. Sequence E1 appears to be derived from the basic sequence of C. aprilinus , etc. ( Wuelker 1980), by the small inversion In4-11b. The alternative sequence qutE2 is then derived from qutE1 by the simple inversion In2d-5 ( Fig. 5 View FIGURE 5 d,e).

Heterozygotes qutE1.2 ( Fig. 6 View FIGURE 6 ) have been found in both populations, and a homozygote E2.2 was found in Connecticut.

Arm F. There are two sequences of arm F. It has not been possible to clarify the whole banding sequence, but band groups 9-7 are distal, following group 1 ( Fig. 4 View FIGURE 4 ), suggesting the sequence is based on the inversion 9- 2, typical of the C. decorus cytological group. However it is not clear how much of that inversion remains beyond about group 5. The alternative sequence, qutF2 is known only from heterozygotes ( Fig. 6 View FIGURE 6 ) in both populations, indicating a simple inversion of about two thirds of the arm, with approximate limits as shown in Fig. 4 View FIGURE 4 .

Arm G. The general features of this arm - extent of pairing and position of the nucleolus and BRs have been given above. The virtually terminal nucleolus and the lack of pairing at this end of the chromosome is in common with a number of other members of the C. decorus -group, such as C. decorus (sp. 3a) ( Martin et al. 1979); C. decorus -group species 2 ( Butler et al. 1995), C. decorus (sensu Rothfels and Fairley 1957) and C. bifurcatus ( Wuelker et al. 2009) . Two sequences for this arm are known, with qutG2 differing by a small simple inversion at the distal end of the chromosome ( Figs. 4 View FIGURE 4 and 6 View FIGURE 6 ). This sequence was found in two specimens at the Old Saybrook locality.