Chironomus antonioi, Correia, Leny Célia Da Silva & Trivinho-Strixino, Susana, 2007

Correia, Leny Célia Da Silva & Trivinho-Strixino, Susana, 2007, New species of Chironomus Meigen (Diptera: Chironomidae: Chironominae) from Brazil, Zootaxa 1504, pp. 53-68 : 57-61

Chironomus antonioi sp. n.

( Figs. 1, 4, 8 , 14, 15 , 23 , 36–41 )

Type material. Holotype male with pupal and larval exuviae. BRAZIL: São Paulo, Luiz Antônio, Boa Sorte Stream, 18.vii.2001, L. Correia ( LEA). Paratypes: 4 larvae, as holotype ( LEA).

Etymology. Named after its type locality, the small town of Luiz Antônio.

Diagnostic characters. The male can be distinguished from other Neotropical Chironomus species on the dark brown foreleg; yellowish brown mid- and hind legs with tarsi, tibia and distal third of femur dark brown; and the yellowish brown abdomen with pale brown markings on tergites I–VI. The pupa is indistinguishable from most described Neotropical species. The larva can be distinguished from other Neotropical species by the following combination of characters: abdomen with rather long lateral and ventral tubules, postmentum and frontoclypeus without pigmentation, mentum with slightly incised trifid median tooth and fourth lateral tooth smaller than fifth lateral tooth, and mandible with three inner teeth.

TABLE 1. Lengths (in µm) and proportions of legs of Chironomus detriticola sp. n., male (n = 4) Male (n = 1)

Length 3.9 mm. Coloration: head yellowish brown, flagellum and maxillary palp pale brown. Thorax ( Fig. 1 ), yellowish brown with brown mesonotal stripes and median region darkened. Sternum yellowish brown; scutellum yellowish; postnotum brownish, darkened in posterior portion. Abdomen ( Fig. 4 ), yellowish brown; tergites I–VI with pale brown markings. Legs ( Fig. 8 ), yellowish brown; foreleg dark brown; mid- and hind legs with distal third of femur, tibia, and tarsi dark brown.

Head. Flagellum 827 µm long; AR = 3.23. Palpomere 2–5 lengths (in µm): 25, 80, 96, 136. Frontal tubercles 20 µm long, about 3 times as long as wide. Dorsal and ventral interocular distance 62 and 179 µm, respectively. Temporal setae 27. Clypeus with 13 setae.

Thorax. Acrostichals 8, biserial, beginning near antepronotum; dorsocentrals 6, partly biserial; prealars 4; supraalar 1. Scutellum with 5 uniserial, transversally arranged setae. Scutal tubercle low.

Wing. Length 1.77 mm. Membrane transparent, without setae; most veins pale brown; RM brown, darker than FCu. Brachiolum with 2 setae, R with 20 setae, R1 with 16 setae, R4+5 with 19 setae in distal 2/3. Squama with 9 setae. R2+3 ends halfway between R1 and R4+5. VR = 1.05.

Legs. Mid- and hind ta1 with 9 and 8 sensilla chaetica, respectively. Lengths and proportions of legs as in Table 2.

Hypopygium ( Fig. 14 ). Anal tergal bands fully enclosing 9 strong setae. Anal point parallel-sided. Superior volsella ( Figs. 14, 15 ), narrow, straight; basal lobe with 8 long setae. Inferior volsella elongate, extending slightly beyond mid-point of gonostylus. Gonostylus strongly inflated, abruptly tapered apically, 137 µm long, with 6 inner marginal setae.

Pupa (n = 1)

Length of abdomen 3.4 mm. Exuviae pale brown.

Cephalothorax. Cephalic tubercles conical, frontal setae 20 µm long. Thorax granulose in anteromedian dorsal region; scutal tubercle present; lateral antepronotals 2, precorneals 2, dorsocentrals 4.

Abdomen. Tergite VI with small posterior patch of shagreen points; T VI–VII with fine shagreenation near anterior margin; T VIII with pair of posteromedian patches of fine shagreen; T V–VI with posterolateral point patches. Conjunctives IV/V and V/VI with fine shagreenation. Hook row continuous, occupying 2/3 width of segment II. Pedes spurii B present on segment II. Pedes spurii A present on segment IV. Spur on segment VIII with 1 apical and 1 short lateral tooth ( Fig. 23 ). Segments I–IV with 0, 3, 3, 3 L setae; segments V–VIII with 4 taeniae. Anal lobe with 1 stout dorsal seta and about 78 taeniate fringe setae.

4th instar larva (n = 5)

Total length 8.0–9.0, 8.6 mm. Coloration: body red; head yellowish, postmentum and frontoclypeus without dark areas.

Head. Ventral head length [248] 212–248, 238 µm; head width [488] 410–488, 443 µm. Antenna ( Fig. 36 ), [246] 189–246, 219 µm long; AR = [1.57] 1.45–1.57, 1.49; ring organ near base; antennal blade surpassing segment three. Pecten epipharyngis ( Fig. 37 ), simple, consisting of about 16 subequal teeth. Premandible ( Fig. 38 ), with two light brown teeth and well-developed brush. SI ( Fig. 39 ), plumose. Mandible ( Fig. 40 ), with yellowish brown dorsal tooth; apical and two inner teeth blackish; inner margin with 2–3 spines. Mentum ( Fig. 41 ), with slightly incised, trifid median tooth; and 6 pairs of blackish, lateral teeth; fourth lateral tooth smaller than fifth. Ventromental plates separated by about 1/5 width of mentum, anterior margin smooth.

Abdomen. Anal tubules with median constriction; lateral tubules about 1/3 as long as 8th abdominal segment; 2 pairs of ventral tubules, 1.8–2.5, 2.0 mm long.

Remarks. The most similar Neotropical males are C. anonymus Williston , C. columbiensis Wülker, Sublette, Morath et Martin , and C. rincon Sublette et Sasa. C. antonioi can be separated from all these species on the coloration of the legs and the abdominal tergites. Further, the strongly inflated and abruptly tapered gonostylus, and the shorter wing length will also separate C. antonioi . The pupa is indistinguishable from most described pupae of Neotropical Chironomus species, except C. stigmaterus which has strong shagreenation on tergites IV–VI. The larvae of C. anonymus , C. columbiensis , C. reissi Correia, Trivinho-Strixino et Michailova , and C. strenzkei are the most similar Neotropical species. However, C. antonioi has a mentum with slightly incised trifid median tooth and the fourth lateral tooth is smaller than the fifth lateral tooth; in C. anonymus , C. columbiensis , C. reissi and C. strenzkei the median tooth is more deeply trifurcate, and the shape of the fourth and fifth lateral teeth also differ from C. reissi and C. strenzkei .

Chironomus antonioi is also similar to the Neartic C. (Lobochironomus) austini (Beck et Beck) , but the adults can be distinguished on the leg coloration and the wing length. The larva can be distinguished on the shape of pecten epipharyngis, as C. austini has several thinner teeth interspersed among normal teeth (see Epler 2001); and the reduced fourth lateral tooth of mentum, which is not reduced in C. austini .

Ecology. Larvae of Chironomus antonioi were collected from roots of macrophytes in a section of the Boa Sorte Stream, located outside Jataí Ecological Station. At the sampling site the bottom substratum is sandy and covered with large stands of aquatic macrophytes, which reduces water flow. Detritus retained in the roots of the macrophytes led to a predominance of detritivores and collectors like Chironomus ( Fonseca-Gessner & Guereschi 2000) .

Figures

FIGURES 1 – 11. Males of Chironomus detriticola sp. n. (3, 7); C. antonioi sp. n. (1, 4, 8); C. phytophilus sp. n. (2, 5, 9); C. oliveirai sp. n. (6, 10); and C. fittkaui sp. n. (11). 1 – 2. Dorsal aspect of thorax. 3 – 6. Dorsal aspect of abdomen. 7 – 11. Fore-, mid-, and hind legs.

FIGURES 12 – 21. Males of Chironomus detriticola sp. n. (12 – 13); C. antonioi sp. n. (14 – 15); C. phytophilus sp. n. (16 – 17); C. oliveirai sp. n. (18 – 19); and C. fittkaui sp. n. (20 – 21). 12, 14, 16, 18, 20. Hypopygium. 13, 15, 17, 19, 21. Superior volsella, ventral view.

FIGURES 22 – 29. Pupae of Chironomus detriticola sp. n. (22); C. antonioi sp. n. (23); C. phytophilus sp. n. (24 – 26); C. oliveirai sp. n. (27 – 28); and C. fittkaui sp. n. (29). 22, 23, 26, 28, 29. Anal spur. 24. Dorsocentrals (Dc 1 and Dc 2, 3, 4). 25, 27. Abdomen.

FIGURES 30 – 58. Larvae of Chironomus detriticola sp. n. (30 – 35); C. antonioi sp. n. (36 – 41); C. phytophilus sp. n. (42 – 46); C. oliveirai sp. n. (47 – 52); and C. fittkaui sp. n. (53 – 58). 30, 36, 42, 48, 54. Antenna. 31, 37, 43, 49, 55. Pecten epipharyngis. 32, 38, 44, 50, 56. Premandible. 33, 39, 45, 51, 57. Labral seta. 34, 40. Mandible. 35, 41, 46, 52, 58. Mentum and ventromental plate. 47, 53. Postmentum.