(Figs. 1–5)
Chaetocladius sp. 7 ES| available from: http://boldsystems.org/index.php/Public_RecordView?processid=ATNA483-10
Holotype, ♂, RUSSIA: Nenets Autonomous Okrug, Yugorsky Peninsula, cape Beliy Nos, lake, N 69,607361º E 60,211639º 6 m, 08.viii.2015, leg. Andrey B. Krasheninnikov (CCK).
Paratypes, 5 ♂, same locality and data as for holotype; 1 ♂, RUSSIA: Nenets Autonomous Okrug, Vaygach Island, Lyamchin Peninsula, neighborhood of Cape Bolshoi Lyamchin Nose, stream, N 69,857806º E 59,147222º 4 m, 07.viii.2015, leg. Andrey B. Krasheninnikov (CCK).
Derivatio nominis. The species is named ‘ spiridonovi ’ in honor of the Russian marine biologist Vasiliy A. Spiridonov (07.04.1957 – 17.12.2020), who devoted many years of his life in studying and preserving the region delimited by the polar latitudes.
Description. Adult male (n = 3)
Total length 2.9–3.1 mm, and abdomen 2.1–2.2 mm. Wing length 1.8–1.9 mm. Ratio total length/wing length 1.60–1.65. Head, thorax, abdomen and legs light brown.
Head. Eye bare, reniform. Temporal setae 8–10 including inner and outer verticals and 1–2 postorbitals.Antenna with partly reduced plume, AR 0.74–0.77. Clypeus with 8–9 setae. Lengths (in μm) of palpomeres): 24–31; 27–43; 122–125; 86–106; 122–149.
Thorax. Lateral antepronotals 4–7; dorsocentrals 10–12; acrostichals 13 (begin close to antepronotum), prealars 4–5. Scutellum with 5–9 setae.
Wing. Brachiolum bare. Membrane with strong punctation under X400 magnification. R with 13–16, R 1 with 3–6, R 4+5 with 0–8 setae; other veins bare. Anal lobe slightly truncated. Costa extending to apex of R 4+5 on 15–30 μm. R 4+5 ending distal to end of M 3+4. R 2+3 weak. Squama with 3–5 setae.
Legs. Fore tibia with 59 μm long spur; mid tibia with 31 μm and 24 μm long spurs; hind tibia (Fig. 5) with 47 μm and 24 μm long spurs. Hind tibial comb consists of 17 setae. Pseudospurs present on: ta 1 -ta 2 of P 2 and ta 1 -ta 3 of P 2. Pulvilli reduced, empodium present. Length (in μm) and proportions of legs as in Table 1.
Hypopygium (Figs 1–4). Tergite IX with 22–26 setae located on each side of the dorsal midline and the basal part of anal point. Anal point 120 µm long, reaching almost apex of gonocoxite, basal part rectangular, protruding dorsally into a characteristic dorsal hump which is clearly visible in lateral view (Fig. 3), basal part with lateral setae. Laterosternite IX with 4–7 setae. Virga 86 μm long consisting of 2 long spines. Transverse sternapodeme 110–125 μm long, phallapodeme 98–102 μm long. Gonocoxite 239–255 μm long. Superior volsella absent. Inferior volsella (IVo) sub-rectangular to large lobe shaped, located on distal part of gonocoxite; dorsal side with 15-20 short setae; posterior margin with characteristic undulation. Gonostylus 71–78 μm long, massively globular with rounded posterior margin; crista dorsalis low, located distally; megaseta 8–12 μm long, well-developed. HR 3.25–3.39.
Female, pupa and larva. Unknown.
Diagnostic characters. The new species is similar to C. crassisaetosus, C. elenae, C. variabilis, C. eugenyii but differs from them in having: anal point very long, with dorsal projection and ending almost at apex of gonocoxite; virga composed of 2 pointed long spines; IVo nearly sub-rectangular, inner and caudal margins with undulation, dorsal side with about 15-20 short setae; gonostylus massively globular, with rounded posterior margin, crista dorsalis low, located distally.
Distribution
The new species is known from its type-locality at the Yugorsky Peninsula, Russia, from the Vaygach Island, Russia and Vidjedalsbekken (upper), Dovre, Rondane nationalpark, Norway (N 61,9717º E 9,83606º 1280 m, 31.viii.2008, leg. T. Hoffstad, sequence ID in BOLD: ATNA 483-10.COI-5P) (Ekrem et al., 2018).