Stenochironomus amazonicus, Dantas, Galileu P. S., Hamada, Neusa & Mendes, Humberto F., 2016

Dantas, Galileu P. S., Hamada, Neusa & Mendes, Humberto F., 2016, Contribution to the knowledge of Stenochironomus Kieffer (Diptera, Chironomidae) from Brazil: seven new species and description of females and immatures of some previously known species, Zootaxa 4117 (1), pp. 1-47 : 3-7

publication ID	https://doi.org/ 10.11646/zootaxa.4117.1.1
publication LSID	lsid:zoobank.org:pub:4274F17E-D096-4B30-8FD2-E66769F49708
DOI	https://doi.org/10.5281/zenodo.6073930
persistent identifier	https://treatment.plazi.org/id/03E32D35-510D-3204-FF04-CCA0F7FCF8FA
treatment provided by	Plazi
scientific name	Stenochironomus amazonicus
status	sp. nov.

Treatment

Stenochironomus amazonicus View in CoL new species

( Figs. 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 )

Type material. Holotype male with pupal exuvia, BRAZIL: Amazonas state, Novo Airão, Km 3 do ramal do Hotel Mercuri, 02º50'44.4" S, 60º54'56.9" W, 13.xi.2008, in decayed wood, G.P.S. Dantas ( INPA). Paratypes: 1 male with pupal exuvia, same locality as holotype collected 02.x.2008; 1 male with pupal exuvia, same as holotype collected 15.x.2008; 1 male, same as holotype collected 25.ii.2009; 1 male, same as holotype collected 30.ii.2009; 2 males, same as holotype collected 07.iii.2009; 1 female with pupal exuvia, same as holotype collected 06.ii.2009; 1 female with pupal exuvia, same as holotype collected 19.vi.2009; 1 female, same as holotype collected 21.ix.2008; 1 female, same as holotype collected 15.x.2008. Additional material: 4 larvae, same as holotype collected 01.ix.2008.

Diagnostic characters. Male: eyes not metallic; anterior ⅔ of scutum dark-brown, extending laterally to parapsidal suture; anal point thin and straight in dorsal view; inferior volsella with two long apical setae of equal size; other setae arranged in an irregular way; gonostylus large at mid region and narrow at extremities. Female: eyes not metallic; anterior margin of scutum with dark pigmentation; median vitta completely pigmented; somewhat circular patch on lateral vitta, extending to parapsidal suture, connected to anterior margin of scutum by a light pigmentation; scutellum without pigmentation; postnotum dark brown; preepisternum brown; T I–III brown, T IV–V light brown; post-genital plate triangle-like and pointed at apex; spherical seminal capsules. Pupae: frontal apotome not elongated; hooklets on T II of equal size; apex of anal lobes with a spur. Larva: mentum with 10 fused teeth; ventromental plate with tubercles on latero-posterior margin; robust anal tubules, with 0–1 constriction.

Etymology. the name amazonicus refers to the Amazonian rain forest, the type locality of the species.

Male (n = 7, except when otherwise stated). Total length 6.53–8.32, 7.38 mm. Wing length 2.72–3.46, 3.13 mm. Total length/ wing length 2.29–2.41, 2.37. Wing length/ length of profemur 2.05–2.18, 2.10. General coloration yellow and dark-brown. Head: eyes not metallic; antennal flagellomere brown with light-brown setae. Thorax: anterior ⅔ of scutum with dark-brown pigmentation, extending laterally to parapsidal suture; scutellum without pigmentation; postnotum dark brown; preepisternum light brown. Legs: front femur yellowish, except apex that is brown, anterior tibia and tarsus brown; mid and hind legs yellowish. Wing: membrane yellowish, distal half slightly darker. Abdomen: T I–IV with brown pigmentation.

Head ( Fig. 1 View FIGURE 1 A). AR 2.44–2.84, 2.71. Thirteenth flagellomerum 1.170–1.530, 1.410 µm long. Temporal setae 19–28, 23. Clypeus with 30–40, 34 setae. Tentorium, stipes and cibarial pump as in Figure 1 View FIGURE 1 A. Tentorium 205–204, 219 µm long; 60–68, 63 µm wide at sieve pore; 21–38, 31 µm wide at posterior tentorial pit. Stipes 21–38, 31 µm long; 8–12, 9 µm wide. Palpomere lengths (1–5 in µm): 38–53, 46; 62–80, 72; 245–295, 270; 116–154, 134; 112– 169, 146. Fifth palpomere small.

Thorax ( Fig. 1 View FIGURE 1 B). Acrostichals 12–15, 13; dorsocentrals 10–16, 12 in a single row; prealars 5–10, 8 in one, two or three rows. Scutellum with 13–23, 18 setae in two rows. Scutum markedly projected anteriorly; anterior edge of scutum angled in lateral aspect.

Wing ( Fig. 1 View FIGURE 1 D). VR 1.10–1.14, 1.12. Brachiolum with 4–7, 5 setae. R with 32–46; 38 setae; R1 with 30–43; 38 setae; R4+5 with 40–65; 51 setae; M with 0 setae; RM with 0–1 setae; remaining veins bare . Squama with 15–24, 19 setae.

Legs. Scale of front tibia 54–69, 62 µm long, with a small spine at apex; spurs of middle tibia 43–55, 50 µm and 50–60, 52 µm long; spurs of hind tibia 43–56, 49 µm and 50–58, 53 µm long. Apex of fore tibia 83–107, 96 µm wide, of mid tibia 91–106, 100 µm wide, of hind tibia 96–125, 115 µm wide. Lengths (in µm) and proportions of legs as in Table 1.

Hypopygium ( Figs.1 View FIGURE 1 C, 2A, 2B, 2C). Anal point thin and straight in dorsal view; dorsal margin straight in lateral view, curved ventrally close to apex and slightly up side curved at apex ( Fig. 2 View FIGURE 2 C); 128–164, 141 µm long; 17–23, 20 µm wide at base; 13–14, 14 µm wide at the midpoint; 11–13, 12 µm wide at apex. Tergite IX with 60– 86, 74 setae, caudal apex wedge-shaped with pre-apical constrictions. Laterosternite IX with 4–7, 5 setae. Phallapodeme curved anteriorly, 175–231, 199 µm long; transverse sternapodeme 55–69, 56 µm long. Gonocoxite 324–367, 342 µm long. Inferior volsella 300–357, 339 µm long, with 10–12, 11 setae arranged in an irregular way, two apical setae long, slim and of equal size; superior volsella 79–96, 86 µm long, with 5–8, 6 setae. Gonostylus large at mid region and narrow at extremities; 288–320, 305 µm long. HR 1.06–1.23, 1.12; HV 2.27–2.60, 2.41.

fe ti ta1 ta2 ta3 ta4

p1 1321–1631, 1499 1390–1745, 1637 1823–2422, 2197 1075–1316, 1234 840–1033, 963 780–967, 887 p2 1301–1624, 1485 1175–1400, 1312 1027–1125, 1057 600–629, 617 424–464, 440 256–290, 275 p3 1500–1850, 1711 1449–1710, 1635 1362–1481, 1420 764–823, 802 592–651, 621 370–384, 376

ta5 LR BV SV BR

p1 258–358, 321 1.31–1.39, 1.34 1.50–1.66, 1.57 1.39–1.49, 1.43 3.6–4.3, 3.9 p2 143–161, 153 0.76–0.81, 0.78 2.55–2.74, 2.65 2.65–2.78, 2.72 3.5–4.7, 4.2 p3 146–171, 158 0.82–0.86, 0.84 2.40–2.55, 2.49 2.40–2.49, 2.42 3.5–5.2, 4.6 Female (n = 5, except when otherwise stated). Total length 7.73–8.00, 7.80 mm. Wing length 3.63–4.60, 4.19 mm. Total length/wing length 1.74–2.13, 1.86. Wing length/length of profemur 1.93–2.42, 2.22. General coloration yellow and dark-brown. Head: eyes not metallic; antennal flagellomere brownish with light-brown setae. Thorax: anterior margin of scutum with dark pigmentation; median vitta completely pigmented; somewhat circular patch on lateral vitta, extending to parapsidal suture, connected to anterior margin of scutum by a light pigmentation; scutellum without pigmentation; postnotum dark brown; preepisternum brown. Legs: anterior femur yellowish with brown apex, anterior tibia dark brown, ta1 with proximal half yellowish and distal half dark-brown, ta2–3 brown, ta4–5 light brown; mid end hind legs yellowish with tibia slightly brownish. Wing membrane grayish, being darkest near the anterior margin and veins. Abdomen: T I–III brown, T IV–V light brown.

Head. Flagellomere length (in µm): 96–164,140; 147–181, 162; 179–199, 188; 178–203, 194; 161–172, 166; 269–305, 286. Longest seta 535–588; 563 µm long. AR 0.32–0.37, 0.34. Temporals 21–27, 25. Clypeus with 31– 52, 43 setae. Tentorium 267–292, 279 µm long; 64–70, 67 µm wide at sieve pore; 25–37, 31 µm wide at posterior tentorial pit. Stipes 227–234, 230 µm long; 9–15, 11 µm wide. Palpomere length (in µm): 44–60, 52; 70–98, 87; 290–346, 320; 162–184, 172; 173–207, 190.

Thorax. Acrostichals 14–17, 16; dorsocentrals 14–22, 17 in two rows; prealars 7–10, 8. Scutellum with 25–36, 29 setae in two rows.

Wing. VR 1.12–1.15, 1.14. Brachiolum with 4–8, 6 setae. R with 55–62, 59 setae; R1 with 66–82, 72 setae; R4+5 with 74–107, 90 setae; RM with 0–2, 1 setae; M with 1–3, 2 setae; remaining veins bare . Squama with 21–31, 27 setae.

Legs. Scale of front tibia 74–84, 79 µm long, with a small spine at apex; spurs of middle tibia 47–56, 50 µm and 61–65, 63 µm long; spurs of hind tibia 53(1) µm and 56–62, 60 µm long. Apex of fore tibia 100–130, 111 µm wide, of mid tibia 106–136, 125 µm wide, of hind tibia 113–155, 135 µm wide. Lengths (in µm) and proportions of legs as in Table 2.

fe ti ta1 ta2 ta3 ta4

ta5 LR BV SV BR

p1 258–358, 321 1.31–1.39, 1.34 1.50–1.66, 1.57 1.39–1.49, 1.43 3.6–4.3, 3.9 p2 143–161, 153 0.76–0.81, 0.78 2.55–2.74, 2.65 2.65–2.78, 2.72 3.5–4.7, 4.2 p3 146–171, 158 0.82–0.86, 0.84 2.40–2.55, 2.49 2.40–2.49, 2.42 3.5–5.2, 4.6 Genitalia ( Figs. 3 View FIGURE 3 A, 3B). Tergite IX with 100–112, 106 setae; gonocoxite IX with 3–5, 4 setae. Cercus 174– 217, 195 µm long. Notum 347–402, 379 µm long. Coxosternapodeme IX 161–222, 194 µm long. Post-genital plate triangle-like and pointed at apex. Spermathecal duct annulated. Seminal capsules with 100–113, 107 µm diameter.

Pupa (n = 2, except when otherwise stated).

Total length 7.52–9.58 mm. General coloration brown.

Cephalothorax ( Figs. 4 View FIGURE 4 A, 4B). Frontal apotome not elongated ( Fig. 4 View FIGURE 4 A); frontal warts absent. Precorneal setae 65–40 µm long. Dorsocentrals (Dc) 66–77 µm long. Distance between Dc1 and Dc2 5–6 µm; between Dc2 and Dc3 377–496 µm; between Dc3 and Dc4 5–6 µm. Median suture granulose.

Abdomen ( Figs. 4 View FIGURE 4 C, 4D). T I bare ; T II–V with large field of shagreen, being thicker near the anterior margin; T VI with central field of shagreen, extending laterally on posterior margin; T VII without shagreen; T VIII with an anterolateral pair of fine shagreen patches; anal segment with anterior pair of shagreen patches. T II with posterior row of hooklets extending to lateral margin of tergite, divided medially into two groups by 30–40 µm, each row 346–523 µm long; pedes spurii B present ( Fig. 1 View FIGURE 1 E). Abdominal setation: S I without L setae; S II–IV with 4 L setae; S V–VII with 4 LS setae; S VIII with 5 LS setae. Spur on S VIII with 5–6 brownish teeth ( Fig. 4 View FIGURE 4 E). Genital sac 557–611 µm long, overreaching the posterior margin of the anal lobe by 62–75 µm; apex of anal lobe bearing a spur; apex of anal lobe rounded, with fringe of about 110 filaments.

Fourth-instar larva (n = 5, except when otherwise stated).

Total length 14.47–14.96, 14.80 mm. Head capsule 0.72–0.77, 0.74 mm.

Head ( Fig. 1 View FIGURE 1 F). Antenna as in Figure 5 View FIGURE 5 A; lengths of antennal segments (in µm): 73–80, 77; 20–26, 23; 14–17, 16; 10–14, 13; 4–5, 4. Blade 22–25, 23µm long. Labrum as in Figure 5 View FIGURE 5 B. Labral lamellae with spicules arranged linearly along a wide margin, spicules of pecten epipharyngis arranged in three groups ( Fig. 5 View FIGURE 5 B). S1 palmate, 34 (1) µm long; S2 pinnate, 31–35 (2) µm long; S3 simple, 35 (1) µm long. Premandible 82–102, 95 µm long. Mandible ( Fig. 5 View FIGURE 5 C) 197–234; 219 µm long, with inner teeth fused. Mentum concave ( Fig. 5 View FIGURE 5 D) 110–132, 123 µm wide, with 10 blackish teeth, the four median teeth being fused, but in some specimens it is not possible distinguish them; micropore located postero-laterally in relation to the setae submenti; ventromental plate with a tubercle on posterolateral margin; in some specimens there are weak crests near anterior margin. Base of dorsolateral strip originating at the midpoint of the dorsomedian strip. Labiohypopharynx ( Fig. 5 View FIGURE 5 E) with ligular lobes somewhat square form, cleft between lobes V-shaped.

Abdomen. Procercus with 8 filaments; associated seta of equal size. Anal tubules robust ( Fig. 5 View FIGURE 5 F), with one constriction (sometimes difficult to observe); basal portion 212–219 (2) µm; apical portion 448–517 (2) µm long. The longest anal hook 108–112 (2) µm long.

Egg (n = 5). Form elliptical, general coloration brownish ( Fig. 1 View FIGURE 1 G); 310–335; 328 µm long and 163–180; 175 µm wide.

Systematic remarks. The color pattern of the abdomen of S. amazonicus sp. nov. is share only by the Japanese species S. membranifer Yamamoto , but the two species can be easily differentiated by the shape of the anal point and by the apical setae of inferior volsella. The anal point of S. amazonicus sp. nov. is thin, straight and parallel-sided in dorsal view, and the two apical setae of inferior volsella are long and slim, contrasting with the anal point of S. membranifer which is comparatively stout, constricted in the middle, widening distally and rounded at apex, and the apical setae of inferior volsella which is short and stout.

Notes on biology of the species. The wood containing larvae of S. amazonicus sp. nov. was collected in a small stream in an area with rapid flow. The trunk measured about 3 m long and 20 cm in diameter, it was firm, solid and still had the bark attached, indicating an initial stage of decomposition. In the field, larvae were found mining between the bark and the trunk. In the laboratory, a part of the trunk was broken up and the larvae were found mining the inner parts as well.

The wood was kept in the laboratory in an aerated aquarium for a period of 14 months. Adults began to emerge at the end of August 2008, about ten days after collection. The last adult emerged in October 2009. The vast majority was female. One of the females had the abdomen filled with eggs. Females are much larger and more robust than males and have a different color pattern, so the association was only possible by comparing the immature stages. The abdomen of the pupa remains partially within the larval exuvia, and sometimes even after the emergence of adults the pupal exuvia remains partially within the larval exuvia, which facilitates the association between these two stages.