Stempellinella chirka, Orel, 2023

Orel, Oksana V., 2023, Stempellinella Brundin, 1947 (Diptera: Chironomidae) from Eastern Siberia and the Russian Far East, with the description of new species, Zootaxa 5380 (4), pp. 341-360 : 345-351

Stempellinella chirka sp. nov.

Figs 8–34 .

http://zoobank.org/NomenclaturalActs/ F96C60BD-ABBE-4E37-94F7-4BA034B97BE7

Stempellinella sp. 1 Makarchenko et Orel, 2023: 145.

Type material. HOLOTYPE: male, RUSSIA: KHABAROVSK TERRITORY, Bolshekhekhtsyrsky Reserve, Chirka river basin, Odyr River , 19.vi.2016, leg. N. Yavorskaya. PARATYPES: 4 males, same data as holotype; Zolotoy Stream , 20.vi.2015 , 5 males, leg. N. Yavorskaya; mouth of the Svetlaya River , 23.vii.2006 , 1 male, leg. N. Yavorskaya; PRIMORSKY TERRITORY, Khasansky District, Barabashevka River , 31.v.2003 , 2 males, leg. T. Tiunova; Lazovsky district, Lazovsky reserve, Pryamushka river basin, Kaplanov Stream , 10.vii.2007 , 3 males, leg. O. Zorina; SAKHALIN REGION, Sakhalin Island, Tymovsky District, Tym River in the area of the mushroom cooker, 27.vii.2003 , 10 males, leg. E. Makarchenko.

Derivatio nominis. From the type locality Chirka River, into which the Odyr River flows—one of the habitats of the new species.

Diagnosis. Male: yellowish brown coloured species, with wing 1.06–1.34 mm long. AR 0.82–1.00; ultimate flagellomere 264–360 μm; length of 2–4 flagellomeres of maxillary palpomeres 282–318 μm; frontal tubercles conical, 9–18 μm long. LR PI 1.51–1.55; combs of mid and hind tibiae with 1 strong spur. Anal tergite with transverse anal tergite band; 2–6 strong median setae; lateral setae 0–2; anal point with strong spinulae at base (7–14); superior volsella oval; median volsella oval or round shape, 21–30 μm long, cover with microtrichia and with 10–15 small setae.

Pupa: frontal tubercles well-developed, tubular, 30–36 μm long; frontal setae taeniate, 195–225 μm long; frontal apotome without granulation. Thoracic horn 315–330 μm long, elongate, with minute spines on distal part; tergite II with comparatively large, triangular shagreen on distal half, hook rows with 35–48 hooks; III–V with π-shaped small median shagreen; VI with π-shaped small median shagreen and two anterolateral patches of spines; VII in proximal part with two patches of shagreen; laterosternites IV–VI with shagreen; anal lobes with fringe of 16–20 taeniate setae.

Larva: clypeal seta S 3 simple. Spur on anal pedestal moderately developed, blunt; AR 0.82–1.00; proximal Lauterborn organ placed at 1/3 length of segment 2 on short pedicel, apical Lauterborn organ placed on pedicel 12 μm long; blade extending to antennal apex and extends beyond top of antenna and apical Lauterborn organ. Premandible with 3 apical teeth and 1 small basal tooth.

Description. Adult male (n=9). General colour yellowish brown. Total length 1.3–1.5 mm; total length/wing length 1.12–1.36.

Head ( Figs 8–9 ). Frontal tubercles conical, 9–18 μm long. Temporal setae 5–8. Clypeus with 7–10 setae. Maxillary palp yellowish, 282–318 μm long; lengths of last 4 palpal segments (μm): 24–30, 54–69, 81–90, 105–129. Palp length/head width 0.98–1.06. Scapus brown, flagellomeres (1–10) dark-brown, 568–720 μm long. AR 0.82–1.00. Ultimate flagellomere 264–360 μm long. Antenna length/palp length 2.11–2.26.

Thorax. Ground colour of scutum yellowish brown, mesonotal strips brown or dark brown. Ac 8–11, Dc 5–8, Pa 1. Scutellum yellowish or yellowish brown, with 6–7 setae. Postnotum brown.

Wing length 1.06–1.34 mm ( Fig. 10 ). R, R 1 with 32–43 setae, R 4+5 with 17–30 setae, Cu 1 with 10–12 setae, M 3+4 with 15–23 setae, Cu with 13–20 setae, An with 18–23 setae. VR 1.4–1.6.

Legs ( Table 3 ). Legs yellowish. Fore tibia with 12 mm long spur; terminal combs of Ti 2 and Ti 3 with 1 strong spur, 27–30 μm long. BR 1 3.7–3.0, BR 2 3.8–5.8, BR 3 6.4–6.6. Sensilla chaetica on Ta 1 P 2 absent.

Abdomen. Yellowish.

Hypopygium ( Figs 11–16 ). Anal tergite with transverse anal tergite band; 2–6 strong median setae; lateral setae 0–2; small microtrichia-free areas present on each side of anal point base.

Anal point 18–30 μm long, wide at about apical 1/3, apically thin and pointed; 7–14 strong spinulae between well-developed anal crests; 10–12 lateral setae at anal point base. Gonocoxite 54–66 μm long; with 3–4 setae along inner margin. Width of transverse sternapodeme 33–45 μm. Phallapodeme 45–60 μm long. Superior volsella oval, 21–30 μm long, with 3–6 dorsal and 3 median setae, without microtrichia. Digitus absent. Median volsella oval or round shape, 15–38 μm long and 21–24 μm wide, cover with microtrichia and with 10–15 small setae. Inferior volsella 39–51 mm long, apically club-shaped, with 4–5 distal setae. Gonostylus 39–45 μm long, with 2–4 setae in apical part and 1 apical seta. HR 1.20–1.54.

Female unknown.

Pupa (male n=1, female n=2)

Cephalothorax. Length of thorax 0.58–0.61 mm. Granulation in anterior half of thorax, a few stronger granules present along median suture line. Frontal tubercles well-developed, tubular or broad conical (depending on the position on the preparation), 30–36 μm long ( Figs 17 , 21 ). Frontal setae taeniate, 195–225 μm long. Thoracic horn 315–330 μm long, elongate, gradually tapering towards apex, with minute spines on distal part ( Figs 18 , 22 ). Antepronotals 2 (195–225 μm long, median and lateral, taeniate). Precorneals 3 (165–195 μm long, taeniate). DC 1–4 simple, 30–36 μm long. Distance between DC 1 and DC 2, DC 3 and DC 4 3 μm, DC 2 and DC 3 66–81 μm. Wing sheath 680–840 μm long, 240 μm wide. Prealar tubercle well-developed. Granulation on the thorax is poorly developed.

Abdomen ( Figs 19–20 , 23–25 ) 1.5–1.7 mm long. Tergite I bare; tergite II with comparatively large, triangular shagreen on distal half, hook rows with 35–48 hooks; III–V with π-shaped small median shagreen; VI with π-shaped small median shagreen and two anterolateral patches of spines; VII in proximal part with two patches of shagreen; VIII with two anterolateral patches of shagreen. Pedes spurii B present; pedes spurii A well-developed on sternite IV. Laterosternites IV–VI with shagreen. Sternites without shagreen. Segment VIII with 1–2 strong dark spurs, 18–39 μm long, covered with small spines. Segment II with 3 L setae, III–IV with 2 L and 1 taeniate L seta; V with 3 LS setae, VI–VII with 4 LS setae, and VIII with 3 LS setae. Anal lobe well developed with complete fringe of 16–20 taeniate setae in single row, dorsal setae absent. Anal segment 120 μm long and 160 μm wide, with two anterolateral patches of shagreen.

Fourth instar larva (n=2). Colouration white (in alcohol), with yellow head capsule 0.9 mm long and 0.7 mm wide.

Head. S 3 simple. Antenna situated on pedestal (30 μm long and 45 μm wide) with pronounced distal spur (21 μm long and 15 μm wide) ( Fig. 31B ). Antenna ( Figs 26, 31A ) 5-segmented, total length 120 μm, length of each segment (in μm): 54–60; 30–33; 12–15; 12; 6. AR 0.82–1.00. Ring organ located at base of basal segment; seta strong, 45 μm long, located 9 μm from base of basal segment next to ring organ. Lauterborn organ large 27–30 μm long, proximal Lauterborn organ placed at 1/3 length of segment 2 on short pedicel, apical Lauterborn organ placed on pedicel 12 μm long. Blade 99 μm long, situated apically on basal segment, extending to antennal apex and extends beyond top of antenna.

Labrum ( Figs 27–28 ). S I 18 μm long, comb-like; S II 24–27 μm long, plumose, situated on tall pedestal 9–15 μm long; S III 15 μm, simple. Pecten epipharyngis consisting of 3 chaetae. Premandible ( Fig. 32 ) 39–51 μm long, with 3 large apical and 1 small basal tooth; brush present.

Mandible ( Figs 29, 33 ) 72–90 μm long, with pale dorsal tooth, with brownish apical and 3 inner teeth. Seta subdentalis 30–42 μm long, curved. Maxillary palp 3-segmented, 18–24 μm long; length of each segment (in μm): 9–15; 4.5; 3.0–4.5.

Mentum ( Figs 30, 34 ) 54–60 μm wide, with 13 teeth, 1 median pale tooth (6 μm wide) and 6 pairs lateral teeth; medial and first lateral teeth lighter than other lateral teeth. Ventromental plate 45–54 μm wide, 30 μm high; distance between ventromental plates 30 μm.

Body. Posterior parapods with 16 simple hooks. Procerci 21 μm long and 18 μm wide. Anal tubules conical, 39–45 μm long.

Remarks. The males of a new species are well distinguished from all known species of this genus by the lobed shape of the median volsella ( Fig. 16 ). The pupa of new species is most similar to Stempellinella sp. A ( Ekrem 2007: 1452, Fig. 31 ), but there are several minor differences, namely, the shape of the frontal tubercles (but the shape can change under the pressure of the coverslip, as in our case (see Figs 17 , 21 )) and the absence of shagreen on laterosterite VI in Stempellinella sp. A . All other morphometric characters are identical, which suggests that the pupa of Stempellinella sp. A belongs to the species Stempellinella chirka sp. nov. But to establish synonymy, additional research is necessary. The larva of a new species differs from all known species of this genus by a combination of features listed in the Diagnosis section (see above).

Distribution. Distributed in Russian Far East— Primorsky Territory, Khabarovsk and Sakhalin Regions.

Figures

FIGURES 8–16. Details of the structure of the male of Stempellinella chirka sp. nov. 8—head; 9—antenna; 10—wing; 11, 15—hypopygium, dorsal view; 12, 14—hypopygium, ventral view; 13—hypopygium, lateral view; 16—superior, median and inferior volsellae, dorsal view. Scale bar 20 µm (8–14), 50 µm (15–16).

FIGURES 17–20. Details of the structure of the pupa of Stempellinella chirka sp. nov. 17—frontal apotome; 18—thorax, lateral view; 19—tergites I–V; 20—tergites VI–IX. Scale bar 20 µm.

FIGURES 21–25. Details of the structure of the pupa of Stempellinella chirka sp. nov. 21—frontal tubercles; 22—thorax, lateral view; 23—tergites II–III; 24—tergites VI–VII; 25—tergite VIII. Scale bar 50 µm.

FIGURES 26–34. Details of the structure of the larva of Stempellinella chirka sp. nov. 26, 31A—antenna; 31B—antennal pedestal with spur; 27–28—labrum; 29, 33—mandible; 30, 34—mentum and ventromental plates; 32—premandible. Scale bar 20 µm (26–30), 50 µm (31–34).