Pagastia (P.) orientalis (Tshernovskij), 1981

Semenchenko, Alexander A., Yagodina, Viktoriia D., Seliverstov, Nikita A. & Makarchenko, Eugenyi A., 2024, Morphological redescription and population genetics of Pagastia (Pagastia) orientalis (Tshernovskij, 1949) (Diptera: Chironomidae: Diamesinae), Zootaxa 5555 (1), pp. 57-74 : 62-66

Pagastia (P.) orientalis (Tshernovskij)

( Figs. 2–32 )

Syndiamesa orientalis Tshernovskij, 1949: 99 ; Linevich 1959: 21; Pankratova 1970: 72; Makarchenko 1977: 118.

Syndiamesa bathyphila Lipina, 1949: 197 .

Pagastia orientalis (Tshernovskij) Makarchenko 1981: 93 , 1985: 46; 2006: 268, 479, 617; Linevich & Makarchenko 1989: 20; Linevich et al 1991: 221, 2002: 60; Makarchenko & Makarchenko 1999: 237, 2000: 173; Ashe & O’Connor 2009: 295.

Material examined. RUSSIA: 6 adult males, Altai Republic, Chemalsky District, Katun’ River, near the mouth of the Chemal River , 29.IV.1989, leg. E. Makarchenko ; 1 adult male, the same data, excepted Sema River , 23.IV.1989, leg. E. Makarchenko ; 6 adult males, 6 pupae, 6 larvae, Irkutsk Region, Baikal Lake basin, Bolshiye Koty Village, Bolshaya Kotinka River , 17–24.VIII.1955, leg. A. Linevich ; 2 adult males, 2 pupae, 2 larvae, the same data, excepted 17–21.VIII.1983, leg. L. Kravtsova ; 2 larvae, Transbaikal Region, Unda River in the vicinity of the Baley Village, 51.654892 N, 116.851810 E, Galgatai River , 50.288373 N, 112.216171 E, leg. P. Matafonov ; 1 adult male, 5 larvae, Republic of Sakha-Yakutia, environs of the Neryungri City, Amnunnykta River , about 1 km above the confluence with the Chulman River , 56.690267 N, 124.748833 E, 2.VIII.2010, leg. E. Makarchenko ; 1 adult male, Khabarovsk Territory, Verkhnebureinsky District, Yagdynya River ( Bureya River basin), 50.593889 N, 132.405000 E, 12. VI.2024, leg. N. Yavorskaya ; 6 adult males, Khabarovsk Territory, Nanaisky District, Anyuisky National Park , Pihtsa River (tributary of Gassi Lake , Amur River basin), 48.796733 N, 136.783783 E, 22–24. V.2019, leg. N. Yavorskaya ; 3 adult males, Khabarovsk Territory, Solnechny District, Badzhal National Park , Kurkaltu River , 29.VIII.2024, leg. N. Yavorskaya ; 4 adult males, the same data, excepted Ulkao River , 30.VIII.2024, leg. N. Yavorskaya ; 12 adult males, Jewish Autonomous Region, Oblutchensky District, in the vicinity of the Teplye Klyuchi Village , Bidzhansky Fish Hatchery , Fedotkin Spring ( Bidzhan River basin), 5.IV.2016, leg. E. Makarchenko ; 4 adult males, Primorye Territory, Khasansky District, Kedrovaya Pad Nature Reserve , Kedrovaya River , 27–30.III.1975, leg. E. Makarchenko ; 1 adult male, the same data, excepted Barabashevka River , 28.III.1976, leg. B. Zakharov ; 2 adult males, Chuguevsky District, outskirts of Verkhneussuriysk stationary station, Berezovy Stream , 30.VII.1975, leg. L. Zhiltsova ; 1 adult male, Ternei District, Sikhote-Alin Nature Reserve, Yasnaya River , mouth, 11.IX.1983, leg. E. Potikha ; 1 adult male, Sakhalin Island, Tymovsky District, vicinity of Kirovskoye Village , spring in Tym River basin, 20.1 X.1979, leg. E. Makarchenko ; 1 adult male, 8 larvae, Kamchatka, Kirpichnaya River , 13. V.1971, leg. T. Nikolaeva ; 1 adult male, the same data, excepted Dalnyaya River , 7. VI.1989, leg. T. Vvedenskaya ; 22 adult males, Magadan Region, the outskirts of Magadan, Snezhnaya Dolina Village, Dukcha River , 16.VIII.1977, leg. E. Makarchenko ; 4 adult males, the same data, excepted Olsky District, Ola River , 19 km, 59.658056 N, 151.299997 E, leg. E. Khamenkova ; 1 adult male, 5 pupae, the same data, excepted Ulukan River in the area of Motykley thermal springs, 16–17.VII.1977, leg. E. Makarchenko ; 1 adult male, the same data, excepted Severo-Evensky District, stream in the area of Tavatum thermal springs, 20.VIII.1977, leg. E. Makarchenko ; 1 adult male, the same data, excepted Tenkiysky District, in the vicinity of the Sibit-Tyellakh Village, Olen Creek ( Kolyma River basin), 10.VII.1977, leg. E. Makarchenko ; 1 adult male, Chukotka Autonomous Okrug, Chukotsky District, Chegitun River , 16.VIII.1981, 66.563333 N, 171.078611 W, leg. E. Makarchenko.

Adult male (n = 27).

Total length 6.0–7.0 mm. Total length/wing length 1.10–1.39.

Coloration. Head, thorax, legs and abdomen brown to dark brown; antennae light brown or grey brown; wings grayish.

Head. Eyes bare and extended dorsomedially. Temporal setae consisting of 4–6 preoculars, 18–21 verticals, and 25–27 postorbitals. Clypeus with 24–46 setae. Antenna with 13 flagellomeres and a well developed plume; pedicel with 3 seta 30–40 μm long; terminal flagellomere with 1 subapical setae 50–59 μm long. AR 1.97–4.20. Palpomere lengths (in μm): 40–60; 128–172; 228–294; 232–294; 200–236. Distal part of palpomere 3 with sensilla capitata 12 μm in diameter. Head width/palpomeres 1–5 length 0.80–1.13.

Thorax. Antepronotum with 7–14 dorsomedial and 11–23 ventrolateral setae. Acrostichals 14–23 (40–52 μm long, in 1–2 rows), dorsocentrals 23–62 (in 1–2 rows), prealars 21–40, scutellars 65–97.

Wing. Length 3.8–5.5 mm; width 0.92–1.3 mm. Membrane without setae. R and R 1 with 32–35 setae; R 4+5 with 14–16 setae; other veins without setae. Costa extension absent. RM length/MCu length 3.0–4.0. Anal lobe developed, protrudes forward. Squama with 49–66 setae (132–140 μm long) in 2 rows. Alula without setae. VR 0.88–0.90.

Legs. Spur of fore tibia 96–128 μm long; spurs of mid tibia 72–92 μm and 78–92 μm long; spurs of hind tibia 84–116 μm and 108–128 μm long. Hind tibial comb with 14–18 setae. Lengths and proportions of leg segments as in Table 2 .

Hypopygium ( Figs. 2–32 ). Tergite IX with 18–27 setae on each side and with an anal point 76–120 μm long and 20–24 μm wide, apically without peg but sometimes bifurcated ( Fig. 24 ). Laterosternite IX with 11–16 setae. Transverse sternapodeme 380–400 μm long. Median aedeagal lobe 176–200 μm long, digitated and widest in distal part; lateral aedeagal lobe 210–284 μm long ( Fig. 26 ).Transverse sternapodeme 380–400 Gonocoxite 288–304 μm long, with well developed basal lobe covered with short setae. Gonostylus 244–260 μm long, ribbed and wrinkled, with different arrangements it has a variety of shapes, in the bent state the distal part is usually located at an angle with megaseta 10–16 μm long. HR 1.12–1.21.

Remarks. Analysis of morphological characters of adult males from different populations of the Eastern Palaearctic showed that there is variability, which is quite acceptable within the species. But it should be noted that the largest individuals, 6–7 mm in length, with longest legs ( Table 3 ) live in the Ola River of the Okhotsk Sea basin, and the highest AR values are found in males from the Kedrovaya River in South Primorye (3.5–4.2) and the Baikal Lake basin (2.96–4.0), the lowest AR (1.97) is found in an specimen from the Olen Stream in the Upper Kolyma River basin. Also noteworthy is the high number of dorsocentrals (58–62) in a male from the Kedrovaya River in South Primorye ( Table 4 ). A comparison of some other features of adult males from different populations is given in Table 4 . The hypopygium of the male is typical for this species, ribbed, with an angular or rounded, depending on the position, distal end, a short terminal spine, a large basal lobe covered with short setae and a long and thin pointed anal point, without a peg or pores, but in the male from the Yagdynia River (Amur River basin) it is bifurcated ( Fig. 24 ). The most atypical gonostylus for the species is in the specimen from the Tym’ River basin on Sakhalin Island, it is narrower than in other males and not ribbed ( Figs. 7–8 ). Unfortunately, there is no DNA barcoding data for this male, which would be desirable to obtain in the future to clarify the species status. Also, the gonostylus of the male from the Yasnaya River in Northern Primorye attracts attention in that in its distal part there is a very long and strong seta, which is absent in representatives from other regions ( Figs. 3–4 ).

Biology. Univoltine species. Flight in the Far East in the Amur River basin (Teplovka River, Teploe Lake of Amur River basin) in April–May ( Levanidov & Levanidova 1962), but in Fedotkin Spring of Bidzhan River basin the emergence of adults can occur periodically from March to September that is, the local population of this species has several cohorts in development. In Southern Primorye flight period from the end of March to the second half of May, in the Magadan Region—in July–August. Larvae and pupae settle on the upper and lateral surfaces of stones at high water flow rates. They live in dense, attached oval cases, sandy on the outside and cobwebby on the inside. In the rivers of Primorye and Kamchatka, larvae prefer to settle on riffles with slightly silted stones and pebbles. The highest altitude (1600 m above sea level) is reached in the Chaibanshan Mountains in China ( Makarchenko 1996).

Distribution. Altai Mountains, East Siberia (Yenisei River, Baikal Lake basin, Transbaikal Territory), Far East (Amur River basin, Khabarovsk and Primorye Territories, North part of Sakhalin Island, Okhotsk Sea basin, Magadan Region, Chukotka), South Korea, China, North America (Alaska).

Figures

FIGURES 2–12. Pagastia (P.) orientalis (Tshernovskij), males from North of Primorye Territory (Yasnaya River) (2–4), South of Primorye Territory (Barabashevka River) (5–6), Sakhalin Island (Tym River) (7–8) and Amur River basin (Teploye Lake) (9–12). 2–3, 6–7, 10–12, gonostylus in various aspects; 4–5, 8–9, hypopygium in dorsal view.

FIGURES 13–19. Pagastia (P.) orientalis (Tshernovskij), males from Kamchatka (Dalnya River) (13–16), East Siberia (Yenisei River) (17–18) and Altai Mountains (Katun River) (19). 13, 17, 19, hypopygium in dorsal view; 14–16, 18, gonostylus in various aspects.

FIGURES 20–24. Pagastia (P.) orientalis (Tshernovskij), males from East Siberia (Yenisei River) (20–21) and Amur River basin (Yagdania River) (22–24). 20–22, hypopygium in dorsal view; 23, gonostylus; 24, anal point.

FIGURES 25–32. Pagastia (P.) orientalis (Tshernovskij), males from Amur River basin (Fedotkin Spring) (25–28), Magadan Region (Ola River) (29–30) and Primorye Territory (31–32). 25–30, hypopygium in dorsal view; 26, lateral and median aedeagal lobes; 27–29, 31–32, gonostylus in various aspects. MAl, median aedeagal lobe; LAl, lateral aedeagal lobe.