Imparipecten sychnacanthus Fusari, Dantas and Hamada, 2018

Fusari, Lívia Maria, Dantas, Galileu P. S., Hamada, Neusa, Andrade-Souza, Vanderly, Lima, Kátia M. & Silva, Janisete G., 2018, Not endemic after all: Imparipecten Freeman, 1961 (Diptera: Chironomidae) described from the Neotropical Region, Zootaxa 4532 (3), pp. 396-406 : 398-403

Imparipecten sychnacanthus Fusari, Dantas and Hamada , sp. n.

( Figs. 2–4 )

Type material. HOLOTYPE: 1 male, BRAZIL, Amazonas, Itacoatiara, Mil Madeireira Itacoatiara Ltda , 3°07’30”S 58°26’52”W, 30.iv.2009, immersed wood, leg. Escarpinati, S. C., Dantas, G. P., (voucher) ( INPA) . PARATYPES: 5 male same data of holotype except 10–22.iv.2009 ; 3 larvae (2 larvae are vouchers), same data of holotype except 18.iv.2009 ( INPA) ; 2 male with pupal exuviae, Amazonas, Barcelos, Rio Ataiana, affluent of Rio Negro , 00°58’56”S 62°54’13”W, 10.viii.2009, immersed wood, leg. Hamada, N., Pes, A. M. O. ( INPA) .

Etymology. The specific name is from Greek sychn (many) and the suffix - acanth Latinized from the Greek akantha (thorn or spine), referring to many spines on the anal spur of pupae.

Diagnostic characters. Imparipecten sychnacanthus sp. n. differs from Imparipecten pictipes by the combination of the following characters. Male: femur brownish; tibia dark brown with frontal area of the distal region white; tarsomere 1 white, tarsomeres 2–5 dark-brown. Pupa: arrangement of shagreen in TV with rectangular area of spinules but absent in vertical median strip and in TVI with rectangular area of spinules but absent in the small median region; anal spur with 7 teeth, the apical one longer than the other six. Larva: arrangement of mental teeth, with the first lateral tooth shortest, second and third lateral teeth fused and large, fourth to seventh on an even slope decreasing in size laterally.

Male (n = 8). Total length 5.57–6.32 mm. Wing length 2.83–2.89 mm. Total length/wing length 2.0–2.2. Wing length/length of profemur 1.6–1.7.

Coloration. Head light-brown. Thorax dark-brown; halteres light-brown; wing without macula, two dark markings in cells r 4+5, one in m 1+2, in m 3+4 and cu. Foreleg with femur brownish, tibia dark brown with frontal area of the distal region white; tarsomere 1 white, tarsomeres 2–5 dark-brown; mid and hind legs with femur and tibia brownish, tarsomere 1 anterior 2/3 light-yellow and brownish apically, tarsomeres 2–5 brownish. Abdominal segments brown.

Head. Eyes bare, frontal tubercles absent. AR 2.5–2.8, antenna with apical flagellomere 1204–1316 µm long, basal 12 flagellomeres 457–484 µm long. Temporal setae 22–29. Clypeus with 44–55 setae. Palpomere lengths (1– 5 in µm): 56–87; 89–94; 276–303; 256–297; 403–439.

Wing. VR 1.07–1.10. Brachiolum with 3 setae. R with 11–13 setae; R 1 with 8–12 setae; R 4+5 with 17–28 setae. Squama with 5 setae. Anal lobe weak.

Thorax. Scutum without tubercle. Dorsocentrals 11–14; acrostichals 8–10; prealars 5–6. Scutellum with 14–17 setae biserial.

Legs. Scale of fore tibia rounded. Spur of mid tibia 42–46 µm long. Spur of hind tibia 46–52 µm long. Length (in µm) and proportion of legs as in Table 2.

Hypopygium ( Fig. 2 A–D). Tergite IX with 23–28 median setae. Anal tergite band well developed. Anal point 82–101 µm long. Phallapodeme 99–124 µm long, transverse sternapodeme 71–89 µm long. Gonocoxite 234–250 µm long. Total length of superior volsella ( Fig. 2D ) 111–129 µm long. Inferior volsella ( Fig. 2C ) 160–198 µm long. Gonostylus 187–219 µm long. HR 1.07–1.34; HV 2.63–3.01.

Pupa (n = 2) Medium-sized, up to 7mm long.

Coloration. Thorax, cephalic area and anterior abdominal segments brown, remainder segments pale-brown, apophyses weakly darkened.

Cephalothorax. Frontal setae present, cephalic tubercles absent. Frontal apotome wrinkled, without frontal warts ( Fig. 3A ). Thoracic horn with two thick branches apically plumose; basal ring well developed, oval. Median suture moderately rugose, with some linearly arranged spines close to suture. Prealar tubercle absent. Two setae antepronotals, 1 dorsal 50 µm long and 1 lateral 14 µm long. Two precorneals setae. Four dorsocentrals: Dc 1 31– 32, Dc 2 28–38, Dc 3 26–36, Dc4 31 µm long. Distance between Dc1 abd Dc 2 15–20 µm, between Dc2 and Dc3 171–200 µm, and Dc3 and Dc4 of 18–29 µm.

Abdomen ( Fig. 3B ). Tergite I bare, TII with subquadrate area of spinules, broader anteriorly but otherwise differentiated only by slightly stronger spinules in the anterior sector, TIII and TIV with rectangular area of spinules, TV with rectangular area of spinules but absent in vertical median strip, TVI with rectangular area of spinules but absent in the small median region, TVII–VIII with small antero-lateral spinule area. Anal segment bare. Tergite II with a continuous row of hooks, with 50% of the tergite width. Conjunctive III/IV and IV/V with a wide band of spine. Sternites II–VIII with fine spinules, more retricted to anterior area on posterior sternites. Pleura bare except spinose on posterolateral corner of V and VI. Pedes spurii A on IV–VI; pedes spurii B well developed on segment II. Anal spurs 91–99 µm long, formed by 7 teeth, one apical longer and six smaller ( Fig. 3C ).

Setation. Segment I with 2D, 1V and without L setae; II–VII with 5D, 3V; 3L on II–IV, V–VII with 4 taeniate setae and VIII with 5 taeniate setae; VIII with 1D, 2V setae. All tergites with a pair of oral setae. Anal lobe with uniserial fringe of 50+ taeniate setae, with narrow taeniate dorsal seta displaced more posteriorly than usual. Genital sac of male not reaching apex of anal lobes, female genital sac shorter than anal lobes.

Larva (n = 3)

Head. Frontal apotome reticulate, anterior half parallel-sided, without frontal pit; 2 median and 3 lateral labral sclerites ( Fig. 4A ). Pecten epipharyngis with three broad scales, each with 6–8 apically rounded teeth. Premandible with 2 teeth and a strong brush. Antenna 154–169 µm long, with 6 segments ( Fig. 4B ), 88–103, 20–22, 15–17, 13, 11–12 and 4–5 µm long; AR = 1.33–1.57. Accessory blade short, Lauterborn organs alternately on apices of segments 2 and 3. Mandible ( Fig. 4C ) 298–300 µm long, with dark apex and 3 inner teeth, dorsal tooth present, internal seta present, subdentalis seta inserted on ventral surface, somewhat sickle-shaped and extending to innermost mandibular teeth. Mentum 191 µm wide, with a median bifid tooth and seven pairs of lateral teeth ( Fig. 4D ). Median tooth about 0.5 shorter than third tooth. First lateral tooth smallest, second and third laterals teeth fused and large; fourth to seventh on an even slope and decreasing in size laterally, teeth dark. Ventromental plates 219–220 µm wide, medially separated by distance between the fourth lateral teeth. Setae submenti simple.

Distribution. The species is known from the state of Amazonas, Brazil.

Comments. Freeman (1961) and Cranston & Hardwick (1996) emphasize the importance of the shape of the mid- and hind tibial combs as well as the “close approximation of wing vein R2+3 to R1” for the diagnosis of the genus Imparipecten . The shape of the mid- and hind tibial combs in the males analyzed seem close to those of Cranston & Hardwick (1996), but we cannot establish how close the R2+3 and R1 veins are since there is no available measure of this. We also were unable to analyze specimens of I. pictipes morphologically.

Figures

FIGURE 2. Imparipecten sychnacanthus sp. n., male. (A) hypopygium, dorsal view. (B) hypopygium with tergite IX and anal point removed, dorsal view left, ventral view right. (C) Detail of superior volsella. (D) Detail of inferior volsella.

FIGURE 3. Imparipecten sychnacanthus sp. n., pupa. (A) Frontal apotome. (B) Abdomen. (C) Anal spurs.

FIGURE 4. Imparipecten sychnacanthus sp. n., larva. (A) Dorsal sclerites. (B) Antenna. (C) Mandible. (D) Mentum and ventromental plates.