A new species of Chironomus Meigen (Diptera: Chironomidae: Chironominae) from polluted streams of southeastern Brazil
Author
Correia, Leny Célia Da Silva
Author
Trivinho-Strixino, Susana
Author
Michailova, Paraskeva
text
Zootaxa
2006
1130
57
68
journal article
10.5281/zenodo.171889
0110307f-11b5-4dd7-81cf-0746e40e98dd
11755326
171889
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.
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.
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.
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.
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.
TABLE 1.
Lengths of leg segments (in m) and leg ratios (LR) of
Chironomus inquinatus
sp. n.
A. Male. B. Female. BR: bristle ratio.
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.