Stenochironomus oliveirai, Reis, Emiliano De Angelis, Filho, Arlindo Serpa & Ferreira-Keppler, Ruth L., 2013

Reis, Emiliano De Angelis, Filho, Arlindo Serpa & Ferreira-Keppler, Ruth L., 2013, Two new species and records of Stenochironomus Kieffer from Brazilian Amazon region, with description of immature stages (Diptera: Chironomidae), Zootaxa 3710 (5), pp. 449-466 : 450-454

Stenochironomus oliveirai sp. n.

Figs 1–3

Type material. Holotype, BRAZIL, Amazonas State, São Gabriel da Cachoeira, Road next BR 307, point #3, 00º 10'28,2''S, 67º 00'37,4''W, 23–30.VIII.11, collected in submerged leaf, 1 male with pupal and larval exuviae, leg. E.D. De-Angelis-Reis & R.L. Ferreira-Keppler (INPA, slide-mounted in Euparal).

Diagnostic characters. The adult male can be separated from all other Stenochironomus species by the following combination of characters: apex of tergite IX square-shaped, with two distinctly produced lateral broad protuberances covered with fine setae. The pupa is distinct by the presence of rounded frontal warts; dark brown margin of wing sheath; genital sac measuring more than 300 µm of length, extending beyond the apex of anal lobe.

Etymology. This species is honourably named after Dr. Sebastião José de Oliveira, who was the major reference in Chironomidae research in Brazil.

Description. Adult male (n = 1)

Total length 5.43 mm. Wing length 2.25 mm. Wing length/length of profemur 1.49 mm.

Colour. Eyes markedly metallic green, whether specimens were kept alive or in ethanol. Antenna with bristles and flagellomeres light brown. Postnotum dark brown in the ⅔ basal region, dark brown stripe at base of lateral vitae, dark brown median anepisternum, posterior anepisternum and mesepimeron, preepisternum with a dark brown stripe in the anterior region. Fore legs with a dark brown apex of femur; tibia with a dark brown spot in basal region, tarsomeres 1–5 with brown stripes on apices. Mid legs with apex and basal regions of femur with dark brown stripes; tibia with dark brown spot in basal region, tarsomeres 1–5 without markings. Hind legs with apex and posterior basal region of femur with dark brown stripes, tibia with a dark brown spot in apical region, tarsomeres 1–5 without markings. Light brown Wings with a large light brown spot in middle region. Abdomen with dark brown spots on tergite I, located in laterodorsal region extending medially from distal margin, forming a "U" shaped design (in dorsal view); tergites II–IV: brown band on posterior region; tergite IX: dark brown, inferior volsella and gonostylus varying from pale to brownish.

Head ( Fig. 1 A; 1B). AR 2.15, ultimate flagellomere 1000 µm long. Temporal setae 36. Clypeus with 25 setae. Tentorium 204 µm long; 10 µm wide at sieve pore; 12 µm wide at posterior tentorial pit. Stipes 190 µm long; 10 µm wide. Palpomere lengths (in µm): 85; 43; 68; 199; 158.

Thorax ( Fig. 1 C). Ac 12; Dc 16; Pa 5, Scts 14 in two rows. Anterior edge of scutum slightly rounded in lateral aspect.

Wing ( Fig. 1 D). VR 1.07. Brachiolum: 4 setae. R: 42 setae; R1: 54 setae; R4+5: 65 setae; RM: 2 setae; remaining veins bare. Squama: 5 setae.

Legs. Scale of fore tibia 27 µm long; spurs of mid tibia 70 µm; spurs of hind tibia 57 µm. Apex of fore tibia 69 µm wide, mid tibia 118 µm, hind tibia 57 µm. Lengths (in µm) and proportions of legs as in Table 1 .

Hypopygium ( Figs. 1 E; 1F). Anal point 169 µm long, 21 µm wide at base, 20 µm wide at apex; curved in lateral view. Tergite IX: 38 median setae, square-shaped, bearing 16 setae on each side of anal point, with two distinctly produced lateral broad protuberances covered with fine setae. Laterosternite IX: 7 setae. Phallapodeme 99 µm long; transverse sternapodeme 36 µm long. Gonocoxite 232 µm long; inferior volsella 94 µm long, with 5 long slender setae; superior volsella 94 µm long. Gonostylus with broadly rounded apex, 271 µm long. HR 0.85, HV 2.00.

Pupa (n = 1, exuviae)

Total length 6.30 mm. Colour: light brown cephalothorax and abdomen.

Cephalothorax. Frontal apotome elongated with rounded frontal warts ( Fig. 2 A), absent wing tubercle. Precorneal setae 2; 63–69 µm long. Dorsocentrals (Dc) 110–108 µm long. Distance between Dc1 and Dc2 2 µm; Dc2 and Dc3: 299 µm; Dc3 and Dc4: 1 µm; median suture granulose ( Fig. 2 C).

Abdomen ( Fig. 2 B). TI: median, large field of shagreen; TII–V: median, large field of shagreen; TVI: field of shagreen restricted to two patches on anterior and posterior regions; TVII–VIII: bare; anal segment with an anterior pair of rounded shagreen patches. TII: posterior row of hooklets in median region, localized on a flap extending posteriorly on TIII and divided medially into two groups of 44 and 40 µm, by a distance of 23 µm. Abdominal setation: SI with no L setae; SII–IV: 3 L setae; SV–VII: 4 LS setae; SVIII: 5 LS setae. Spur on SVIII with 4–5 brownish teeth ( Fig. 2 D). Genital sac 372 Μm long, overreaching apex of anal lobe by 76 Μm; apex of anal lobe rounded, with a fringe of 46 filaments.

Fourth-instar larva (n = 1, exuviae)

Head. Head capsule 0.60 mm long. Antenna ( Fig. 3 A); lengths of antennal segments (in Μm): 77; 25; 13; 9; 2. Antennal blade 25 Μm long. Labrum damaged. Mandible ( Fig. 3 B) 159 Μm long, containg 3 inner and 1 dorsal teeth. Mentum ( Fig. 3 C) 133 Μm wide and convex, with 10 blackish teeth; micropore located posteriorly to setae submenti; paralabial plate with a light concavity near to mentum and no striae. Base of dorsolateral strip originating from the half of dorsomedian strip. Labiohypopharynx ( Fig. 3 D) with ligular rounded lobes, with a narrow cleft between lobes, nearly parallel-sided to U-shaped structure.

Female unknown.

Distribution and habitat. This species is only known to north of Brazil, Amazonas State, municipality of São Gabriel da Cachoeira. The larva was collected in submerged leaves in a rocky bottom stream of permanent water flow with dense riparian vegetation.

Figures

FIGURE 1. Stenochironomus oliveirai sp. n. Adult male: A—head, B—cibarial pump, tentorial and stipes C—thorax, Dwing E—hypopygium with anal point and tergite IX and dorsal aspect of left gonocoxite and gonostylus F—hypopygium with anal point and tergite IX removed.

FIGURE 2. Stenochironomus oliveirai sp. n., pupa. A—frontal apotome with frontal warts, B—abdomen: tergites I – IX, Ccephalothorax, D—spur on TVIII.

FIGURE 3. Stenochironomus oliveirai sp. n., larva. A—antenna, B—mandible, C—mentum and paralabial plate, Dlabiohypopharynx.

Tables

TABLE 1. Lengths (in µm) and proportions of leg segments of Stenochironomus oliveirai sp. n., male (n = 1).

	fe	ti	ta1	ta2	ta3	ta4
p1	1502	1375	1946	888	814	726
p2	1579	1366	1079	560	453	270
p3	1307	1150	847	417	331	213