Chironomus inquinatus, Correia, Leny Célia Da Silva, Trivinho-Strixino, Susana & Michailova, Paraskeva, 2006

Correia, Leny Célia Da Silva, Trivinho-Strixino, Susana & Michailova, Paraskeva, 2006, A new species of Chironomus Meigen (Diptera: Chironomidae: Chironominae) from polluted streams of southeastern Brazil, Zootaxa 1130, pp. 57-68 : 58-66

Chironomus inquinatus sp. n. ( Figs. 1–17 )

Etymology. The species name is from Latin, inquinatus , meaning polluted, in reference to the habitat where the larvae live.

Type material. Holotype: male with associated pupal and larval exuviae (in Euparal), São Carlos, SP, Brazil, Monjolinho stream (22o01’48.0”S – 48o01’57.8”W), 12.I.2001, leg. L. Correia. Paratypes: 2 males with pupal and larval exuviae, 5 females, 10 larvae (including 5 with chromosome preparations), from the type locality, 12.I.2001, leg. L. Correia; 2 males with pupal and larval exuviae, 1 female pupal and larval exuviae, 10 larvae (including 7 with chromosome preparations), from Araraquara, SP, Brazil, Ouro stream, 16.X.2001, leg. L. Correia; 3 males with pupal exuviae, 2 females with pupal exuviae, 10 larvae (including 5 with chromosome preparations), from São Carlos, SP, Brazil, Tijuco stream, 30. IV.2001, leg. L. Correia.

The holotype and most paratypes are deposited in the Laboratório de Entomologia Aquática (LEA) collection at Universidade Federal de São Carlos, São Paulo, Brazil. Other paratypes are deposited in the Museu de Zoologia de São Paulo ( MZSP), São Paulo, Brazil (1 male with associated pupal and larval exuviae); in the Zoologische Staatssammlung München ( ZSM), Munich, Germany (1 male with associated pupal and larval exuviae); and in the collection of P. Michailova in the Institute of Zoology at the Bulgarian Academy of Sciences, Sofia, Bulgaria (17 larvae with their chromosome preparations and larval morphology).

Morphological description. All character states not described below conform to the generic or subgeneric diagnoses of Wiederholm (1983, 1986, 1989) and Saether (1977).

Male imago (n = 8).

Length about 5.0– 6.5 mm. Coloration: Head. Yellowish brown. Antennal flagellum pale brown. Maxillary palps pale brown. Thorax ( Fig. 1 ). Yellowish brown with brown mesonotal stripes, which are darkened in anterior portions. Sternum yellowish brown. Scutellum yellowish. Postnotum brownish, darkened in median portion and posteromedian groove. Abdomen ( Fig. 2 ). Pale brown; tergites I–V with dark brown markings. Legs ( Fig. 3 ). Yellowish brown; femora, tibiae, and tarsi brownish at apex.

Head: Antennal flagellum 1142 (1062–1469) µm long; AR = 3.25 (3.13–3.72). Palpomere lengths 2–5: 43 (37–43), 191 (179–253), 216 (185–253), 302 (296–401) µm. Frontal tubercles short, 34 (32–49) µm long, about 3–3.5 times as long as wide. Dorsal and ventral interocular distance of 105 (74–117) µm and 247 (210–296) µm, respectively. 43 (41–45) temporal setae. 39 (35–42) clypeal setae. Sensilla near tip of palpomere 3 with 6 hair­like setae.

Thorax: Setal count: Acrostichals 22 (20–22), biserial and beginning near the antepronotum; dorsocentrals 28 (22–33), partly biserial; prealars 7 (6–7); supra­alar 1; scutellars 32 (22–30) uniserial transversally arranged. Scutal tubercle short.

Wing: Length 2.68 (2.37–3.32) mm. Membrane transparent, without setae; most veins pale brown; RM and FCu dark brown, RM darker than FCu. Brachiolum with 3 setae; R, R1 and R4+5 with 37 (34–40), 25 (24–30) and 35 (32–37) setae; R4+5 setae distributed in the distal 2/3 of the vein. Squama with 23 (18–24) setae. R2+3 ends halfway between R1 and R4+5. VR = 1.03–1.04.

Legs: Segment lengths and proportions as in Table 1 A. Mid and hind tarsomere 1 with 17 (10–12) and 21 (17–18) sensilla chaetica.

Hypopygium ( Figs. 4–5 ): Anal tergal bands fully enclosing 14 (14–15) strong setae. Anal point proximally narrow, apex curving to ventral ( Fig. 4 ). Superior volsella ( Figs. 4–5 ) rather stout and strongly curving to ventromedial; basal lobe with 7 (6–10) long setae. Inferior volsella slightly clubbed, not extending beyond midpoint of gonostylus. Gonostylus elongate, 197 (186–238) µm long; distal part slender, with 5 (6–7) inner marginal setae.

Female imago (n = 8).

Total length 6.0–7.0 mm. Coloration as for male, but slightly darker.

Head: Lengths of antennal flagellomeres 2–6: 68–93; 93–136; 99–136; 111–142; 105–136 µm. AR = 0.403–0.404. Maxillary palpomeres 2–5: 49–56; 167–272; 191–253; 309–401 µm. Frontal tubercles short (21–39 µm). Long, about 1.5–1.7 times as long as wide. Dorsal and ventral interocular distance of 56–93 µm and 68–117 µm, respectively. 26–40 temporal setae; 38–42 clypeal setae, sensilla near tip of palpomere 3 with 3 hair­like setae.

Thorax: Setal count: Acrostichals 28–38, biserial and beginning near the antepronotum; dorsocentrals 38–60, partly biserial; prealars 6–9; supra­alar 1; scutellars 27–42, uniserial transversally arranged. Scutal tubercle short.

Wing: Length 2.28–3.34 mm. Membrane transparent, without setae; most veins pale brown; RM and FCu dark brown, RM darker than FCu. Brachiolum with 3 setae. R, R1 and R4+5 with 33–50, 26–48 and 47–55 setae; R4+5 setae distributed in the distal 4/5 of the vein. Squama with 15–30 setae. R2+3 ends halfway between R1 and R4+5. VR = 1.11–1.12.

Legs: Lengths and proportions as in Table 1 B. Mid and hind tarsomere 1 with 60–75 and 83–101 sensilla chaetica.

Genitalia: Gonocoxite IX short, with 3–4 setae. Segment X with 7–11 setae on each side. Sternite VIII with 35–49 setae on each side. Postgenital plate triangular, base 85 µm and height 22 µm. Spermathecal duct slightly curved, 0.9 times shorter than notum.

Pupa (n = 11).

Length of abdomen 6.3–7.6 mm. Exuviae pale brown.

Cephalothorax: Cephalic tubercles conical; frontal setae 185–253 µm long ( Fig. 6 ). Thoracic horn basal ring as in Fig. 7 . Thorax granulose in anteromedian dorsal region; scutal tubercle present. Thoracic chaetotaxy on either side: 2 lateral antepronotals, 2 precorneals, and 4 separated dorsocentrals.

Abdomen: Tergite VI with a pair of small posterior patches of shagreen points; VI and VII with fine shagreen near anterior margin; VIII with pair of posterocentral patches of fine shagreen. V and VI with posterolateral point patches. Conjunctives IV/V, V/VI, and VI/VII with fine shagreen. Hook row continuous, occupying 1/2 width of segment II. Pedes spurii B present on II. Pedes spurii A present on IV. Segment VIII spur with 1 apical tooth ( Fig. 8 ). Segments I–IV = 0,3,3,3 L setae; V–VIII with 4 taeniae. Anal lobe on each side with 1 stout dorsal seta and about 130 taeniate fringe setae.

A Fe Ti Ta1 Ta2 Ta3 Ta4 Ta5 LR BR

LI 1185 1046 1692 846 692 692 354 1.62 2.5

1046–1477 923–1308 1477–2154 754–1062 615–892 600–877 323–431 1.60–1.65 1.6–2.0

LII 1231 1123 692 385 262 185 138 0.62

1154–1600 1015–1354 569–846 354–462 246–323 169–231 108–169 0.56–0.63

LIII 1354 1323 1031 538 415 246 185 0.78

1277–1785 1215–1738 846–1231 508–646 369–523 246–338 169–231 0.70–0.71

B Fe Ti Ta1 Ta2 Ta3 Ta4 Ta5 LR

LI 1108–1631 923–1385 1585–2246 800–1062 662–938 723–969 323–446 1.72–1.62 1.7–2.3

LII 1169–1662 1046–1585 600–815 323–477 231–292 154–215 108–169 0.57–0.51

LIII 1292–1800 1215–1738 877–1277 492–677 369–523 246–308 169–200 0.72–0.73 Fourth­instar larva (n = 30).

Total length 11.5–15.5 mm. Body red; head yellowish, with spot on gular region ( Fig. 9 ).

Head: Ventral head length 248–280 µm, head width 528–634 µm. Antenna ( Fig. 10 ) length 124–173 µm; AR = 2.08 (1.56–2.39); ring organ near antennal base; antennal blade longer than flagellum. Pecten epipharyngis simple, consisting of about 13 subequal teeth ( Fig. 11 ). Premandible bifid with well­developed brush ( Fig. 12 ). SI plumose as in Fig. 13 . Mandible ( Fig. 14 ) with yellowish brown dorsal tooth; apical and 3 inner teeth blackish; inner margin bears 2 or 3 spines. Mentum ( Fig. 15 ) with trifid median tooth and 6 pairs of lateral teeth blackish. Ventromental plates separated by about 1/5 width of mentum; anterior margin smooth.

Abdomen with lateral tubules about 1/3 as long as 8th abdominal segment, and 2 pairs of long, slightly spiral ventral tubules. Anal tubules with median constriction ( Fig. 16 ).

Karyotype (n = 17).

Chironomus inquinatus sp. n. belongs to the pseudothummi cytocomplex, with chromosome arm combinations AE, BF, CD, and G ( Keyl 1962). The centromere regions are well expressed in all chromosomes but slightly heterochromatized ( Fig. 17 ). In arm A, there is one nucleolar organizer (N) and in arm G, one Balbiani ring (BR) is localized near the telomere.

Arm A has the following banding pattern: 1a–e/ 12a–10 / 4–6c / 12bc / 6d–9 /3c– i/ 2 c–1f / 2d–3b ( Figure 17 ). There is one nucleolar organizer (N) near the center of arm A. Chironomus inquinatus sp. n. is five inversions distant from C. columbiensis Wülker et al. and six inversions distant from C. anonymus Williston (Wülker et al. 1989) . In addition, 10 inversions differentiate it from the standard sequences of C. holomelas Keyl as follows: C. inquinatus sp. n. 1a–e 12a– 10 4–6 c 12bc 6d–9 3c– i 2 c–1f 2d–3b 13–19 1 a–e 6c– 4 10–12 abc 6d–9 3b–2d 1f–2c i–3 c 13–19 1 a–e 6c– 4 10–12 abc 6d–9 3c– i 2 c–1f 2d–3b 13–19 1 a–e 6c– 4 10–12 abc 6d–9 3c–3b 2d 1f–2c–i 13–19 1 a–e 6c– 4 10–12 abc 6d–9 2d–3b 3c–1f 2c – i 13–19

C. columbiensis 1a–e 6c– 4 10–12 6d–9 2d–3b 2c–1f 3c– i 13–19

C. anonymus 1a–e 12–10 4–6 c 6d–9 2d–3b 2c–1f 3c– i 13–19

Inter 3 1a–e 10– 12 4–9 2d–3b 2c–1f 3c– i 13–19

Inter 2 1a–e 3b–2d 9–4 12–10 2 c–1f 3c– i 13–19

Inter 1 1–2c 10– 12 4–9 2d–3 i 13–19

C. holomelas 1–2c 10–12 3 i–2 d 9– 4 13–19

(The sites of inversions are shown in bold; intermediates 3, 2, 1 are according to Wülker et al. 1989).

Arm B has two dark bands near the telomere, like those in C. calligraphus Goeldi ( Spies et al. 2002) . The puff, a specific marker indicated as section 7 in C. piger Strenzke ( Dévai et al. 1989) , is near the middle of the arm. The sections indicated as 1 and 2 in Fig. 17 are similar to those located proximal to the telomere of C. anonymus (Wülker et al. 1989) .

Arm C is similar to that of C. anonymus (Wülker et al. 1989) , especially section 1 ( Fig. 17 ), which corresponds to bands located near the telomere of C. anonymus . The “dumbbell” structure (band groups 3–4 sensu Dévai et al. 1989) is located in the middle of the arm (section 2).

Arm D is similar to that of C. columbiensis (Wülker et al. 1989) . However, part of section C (subsection C1) is in an inverted position compared with that of C. columbiensis . The bands in sections “A” and “B” are similar to those of C. columbiensis . The two dark bands, which are the marker bands most characteristic for the pattern in arm D, are located near the centromere region.

Arm E has the following banding pattern: 1–2/ 9–10b/ 3e–a/ 8–3f/ 10c–13. This banding configuration is similar to that in C. columbiensis and C. anonymus (Wülker et al. 1989) , differing by only one inversion (I) inside of section 8–3f ( Figure 17 ). Chironomus inquinatus sp. n. also differs by inversion 3a–9 from the basic pattern of C. luridus Strenzke ( Keyl 1962) .

Arm F has the following banding pattern: 1/ 6b–2/ 11–10–9–8 cb / 7–6c / 13–12–14–15 –16–17–18–19/ 20–23. The banding pattern of the new species is distinguished by three homozygous inversions from C. columbiensis and by seven inversions from the basic pattern of C. piger ( Keyl 1962) :

C. inquinatus sp. n. 1 6b– 2 11–10–9 –8cb 7–6c– 13–12–14–15 –16–17–18–19 20–23

Inter 2 1 6b– 2 19–16 15– 14–12–13 6 c–7–8bc– 9–10–11 20–23 Inter 1 1 16 –19 2–6b 15–13 6 c–7–8bc– 9–10–11 20–23

C. columbiensis 1 16–19 6b– 2 15–13 6c–7–8bc– 9–10–11 20–23

Inter 3 1 2–6b 19–16 15– 12–13 6 c–7–8bc– 9–10–11 20–23 Inter 2 1 2–6b 19–16 15–13–12 6 c–7–8bc– 9–10–11 20–23

Inter 1 1 2–6b 19– 16 15–13–12 11–10–9–8 cb–7–6c 20–23

C. piger 1 2–6b–6c–19–20–23

Arm G has a Balbiani ring near the end opposite the centromere. No nucleolar organizer is present. Both homologues are paired. The band sequences of C. inquinatus , section 6, are similar to band sequences in chromosome G after the Balbiani ring in C. anonymus . In addition, the band sequences in the middle of arm G, sections 2 and 3, are similar to those in the middle of chromosome G of C. anonymus (Wülker et al. 1989) . Figure 17 (a) shows a heterozygous inversion occurring in 29.41% of the individuals, with lack of pairing of both homologues and the resultant change in the relative positions of the Balbiani rings.

Figures

FIGURE 17. Polytene chromosomes of Chironomus inquinatus sp. n.: AE, BF, CD, and G. Arrows indicate centromere positions. Double arrows indicate positions of marker bands or group of bands. BR = Balbiani ring. N = nucleolar organizer. P = puff. Bold letter I indicates section involved in inversion. (a) Heterozygous inversion in arm G. Homologues are unpaired. One homologue has band sequence 6 (BR), 1,2,3,4,5, and the other has 6, 4, 2, 3, 1, 5 (BR) due to inversions.

FIGURES 1 – 5. Chironomus inquinatus sp. n. male imago. 1. Thorax. 2. Abdominal tergites I – VIII. 3. Front, middle, and hind legs. 4. Hypopygium. 5. Superior volsella, ventral view.

FIGURES 6 – 16. Chironomus inquinatus sp. n. 6 – 8. Pupa. 6. Frontal region. 7. Basal ring. 8. Anal spur. 9 – 16. Larva. 9. Head, ventral view 10. Antenna. 11. Pecten epipharyngis. 12. Premandible. 13. Labral seta. 14. Mandible. 15. Mentum and ventromental plate. 16. Lateral, ventral, and anal tubuli.