Chironomus phytophilus, 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 : 61-63

Chironomus phytophilus sp. n.

( Figs. 2, 5, 9 , 16, 17 , 24–26 , 42–46 )

Type material. Holotype male with pupal and larval exuviae. BRAZIL: São Paulo, Brotas, Dourada Reservoir, 12.xii.2002, F.O. Roque ( LEA). Paratypes: 1 male with pupal and larval exuviae, as holotype; 1 male with pupal exuviae, 4 larvae, as holotype except 10.x.2003, S. Trivinho-Strixino ( LEA, MZUSP).

Etymology. From Greek phyton meaning plant and philos meaning beloved, referring to the preferred habitat of the larvae.

Diagnostic characters. The male can be distinguished from other Neotropical Chironomus species on the yellowish brown legs with tarsi, tibia and distal third of femur of foreleg dark brown, ta2–5 and distal third of ta1 of mid- and hind legs dark brown; and the yellowish brown abdomen with tergites I–V with distal brown bands. The pupa differs from other described pupae of Neotropical species by having strong spines near the posterior margin of tergites V–VI. The larva can be distinguished from other Neotropical species by the following combination of characters: abdomen without lateral tubules, with 2 pairs of rather long ventral tubules; postmentum and frontoclypeus without pigmentation; mentum with slightly incised trifid median tooth; antennal blade surpassing segment five; premandible with 4–5 dark teeth; and mandible with three inner teeth.

Male (n = 3)

Length [4.1] 3.9–4.2 mm. Coloration: head yellowish brown, flagellum and maxillary palp pale brown. Thorax ( Fig. 2 ), yellowish brown with brown mesonotal stripes. Sternum yellowish brown; scutellum yellowish; postnotum brownish, darkened in posterior portion. Abdomen ( Fig. 5 ), yellowish brown; tergites I–V with distal brown bands. Legs ( Fig. 9 ), yellowish brown; tarsi, tibia and distal third of femur of foreleg dark brown; ta2–5 and distal third of ta1 of mid- and hind legs dark brown.

Head. Flagellum [1133] 1003–1185 µm long; AR = [3.19] 3.01–3.19. Palpomere 2–5 lengths (in µm): [34] 28–37, [120] 117–123, [139] 133–148, [191] 191–207. Frontal tubercles [11] 8–17 µm long, about 2 times as long as wide. Dorsal and ventral interocular distance [117] 111–117 µm and [209] 179–209 µm, respectively. Temporal setae [24] 12–24. Clypeus with [7] 7–19 setae.

Thorax. Acrostichals [6] 6–7; partly biserial, beginning near antepronotum; dorsocentrals [7] 6–7, partly biserial; prealars [5] 4–5; supraalar [1] 1. Scutellum with [2] 2–5, uniserial, transversally arranged setae. Scutal tubercle low.

Wing. Length [2.31] 2.18–2.49 mm. Membrane transparent, without setae; most veins pale brown; RM brown, darker than FCu. Brachiolum with [3] 3 setae, R with [28] 28–30 setae, R1 with [18] 10–18 setae, R4+5 with [26] 11–26 setae in distal 1/2. Squama with [11] 11 setae. R2+3 ends halfway between R1 and R4+5. VR = [1.09] 1.02–1.09.

Legs. Mid- and hind ta1 with [8] 4–9 and [9] 6–11 sensilla chaetica, respectively. Lengths and proportions of legs as in Table 3.

Hypopygium ( Fig. 16 ). Anal tergal bands fully enclosing [8] 8–9 strong setae. Anal point parallel-sided. Superior volsella ( Figs. 16, 17 ), narrow, slightly curved; basal lobe with [14] 9–14 long setae. Inferior volsella elongate, extending slightly beyond mid-point of gonostylus. Gonostylus large, [183] 168–185 µm long; with [5] 5 inner marginal setae.

Pupa (n = 3)

Length of abdomen [5.0] 4.8–5.0 mm. Exuviae pale brown.

Cephalothorax. Cephalic tubercles conical; frontal setae [35] 32–35 µm long. Thorax granulose in anteromedian dorsal region; scutal tubercle present; lateral antepronotals 2, precorneals 2, dorsocentrals 4. Dc1 and Dc2, 3, 4 as in Figure 24 .

Abdomen ( Fig. 25 ). Tergites V–VI with strong spines near posterior margin, T VII with fine shagreenation near anterior margin, T VIII with pair of posteromedian patches of shagreen. Conjunctives IV/V and V/VI with fine shagreenation. Hook row continuous, occupying 1/2 width of segment II. Pedes spurii B present on segment II. Pedes spurii A present on segment IV. Spur on segment VIII with 1–2 apical teeth ( Fig. 26 ). Segments I–IV with 0, 3, 3, 3 L setae; segments V–VIII with 4, 4, 4, 5 taeniae. Anal lobe with about [140] 137– 140 taeniate fringe setae.

4th instar larva (n = 6)

Total length 8.8–9.5, 8.6 mm. Coloration: body red; head yellowish, postmentum and frontoclypeus without dark areas.

Head. Ventral head length [267] 267–273, 271 µm; head width [502] 469–525, 509 µm. Antenna ( Fig. 42 ), [221] 191–225, 207 µm long; AR = [1.65] 1.34–1.68, 1.54; ring organ near base; antennal blade surpassing segment five. Pecten epipharyngis ( Fig. 43 ), simple, consisting of about 11 subequal teeth. Premandible ( Fig. 44 ), with 4–5 dark teeth and well-developed brush. SI ( Fig. 45 ), plumose. Mandible (as in Fig. 40 ), with yellowish brown dorsal tooth; apical and two inner teeth blackish; inner margin with 2 spines. Mentum ( Fig. 46 ), with slightly incised, partially trifid median tooth; and 6 pairs of blackish, lateral teeth. Ventromental plates separated by about 1/5 width of mentum, anterior margin smooth.

Abdomen. Anal tubules with median constriction; without lateral tubules; with 2 pairs of ventral tubules, 0.4–0.6, 0.5 mm long.

Remarks. The most similar Neotropical males are C. strenzkei and C. latistylus . C. phytophilus can be separated from both species on the coloration of the legs and abdominal tergites. Further, the wing lacks extensive dark markings, which is present in C. strenzkei , and the wing is longer than in C. latistylus . The larvae of Chironomus sp. AR 4 ( Reiss 1974), described from the Amazon, is the most similar Neotropical species. This species has a similar premandible with 4–5 dark teeth and lack lateral tubules on the abdomen, but the two species can be separated on the mentum, which has a slightly incised trifid median tooth in C. phytophilus . Further, the antennal blade is surpassing segment five in C. phytophilus . A premandible with 4–5 dark teeth is unusual in Chironomus larvae, but has been recorded in some Neotropical and Holarctic species (Pin- der & Reiss 1983; Chaudhuri et al. 1992; Epler 2001).

Ecology. Chironomus phytophilus larvae are associated with Mayaca fluviatilis Aublet in the Dourada Reservoir, located in the Environmental Protected Area of Corumbataí in Brotas, São Paulo State. This reservoir has sandy bottom covered with a dense M. fluviatilis carpet. The water is transparent, acid, and well oxygenated, with extremely low conductivity and nutrient concentration ( Melão 1997).

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.