Tanytarsus salmelai, Giłka, Wojciech & Paasivirta, Lauri, 2009

Giłka, Wojciech & Paasivirta, Lauri, 2009, Evaluation of diagnostic characters of the Tanytarsus chinyensis group (Diptera: Chironomidae), with description of a new species from Lapland, Zootaxa 2197, pp. 31-42 : 32-35

Tanytarsus salmelai sp. n.

( Figs 3 , 4 , 15–18 , 21 , 24, 27)

Type material. Holotype male, slide mounted in Canada balsam: Finland, Arcto-Alpine ecoregion, Aksonjunni, 36 km south of Nuorgam, Utsjoki, 2 July 2007. Paratypes. 1 male: same data as holotype; 2 males: Finland, Northern boreal ecoregion, Vasanvuoma near Kittilä, 26 June 2007; 2 males slide mounted in Euparal: Finland, Taljavaaranvuoma near Kittilä, 12 July 2007. Leg. J. Salmela.

Derivation of the name. The specific name is dedicated to Jukka Salmela (University of Jyväskylä, Finland), who collected the material.

Diagnosis. Darkly coloured species, with wing 1.15–1.50 (1.30) mm long and AR 0.44–0.51 (0.48). Anal wing lobe strongly reduced; membrane brownish, covered with sparse macrotrichia apically. Anal point slender, with narrowed and strongly elongated tip. Superior volsella roundish, bearing two anteromedian setae. Digitus stout, with apical pear-shaped lobe and single seta at its base. Stem of median volsella strongly reduced, with group of short lamellae. Inferior volsella parallel-sided, with transversally cut apex and darkly pigmented dorsomedian ridge.

Description. Adult male (measurements in Table).

TABLE. Comparison of measurable characters of male Tanytarsus brundini , T. curticornis and T. salmelai sp. n. (length measurements in μm, except for wing).

Character \ Species T. brundini T. curticornis T. salmelai

n = 10 unless otherwise stated n = 10 n = 6 unless otherwise stated Colouration. Ground colour of thorax, scutellum, haltere, legs and abdomen olive brown; antennal pedicel, tentorium, scutal stripes, postnotum and sternum brown to fuscous or black; wing membrane brownish; C, M and radial veins distinctly darker.

Head. Antenna with 13 flagellomeres; ultimate flagellomere relatively short, club-shaped. Frontal tubercles short but always present. Third palpomere longer than fourth.

Wing. Membrane covered with sparse macrotrichia in distal half of cell r4+5, a few macrotrichia in apical part of cell m1+2 sometimes present, remaining cells bare. Veins Sc, M, RM, R2+3, proximal half of R4+5, M1+2, Cu and false veins bare, remaining veins bearing sparse macrotrichia. R4+5 ending slightly distal of M3+4 and well proximal of M1+2, FCu distinctly distal of RM, R1 and Cu1 ending about same distance along length of wing. Anal lobe of wing strongly reduced ( Fig. 3 ).

Legs. Spur of fore tibia straight, 20–25 μm long. Combs of mid and hind tibiae separated. Each comb consists of 7–9 teeth 12–15 μm long (mid tibia) and 8–10 teeth 16–20 μm long (hind tibia); each comb bears straight or slightly curved spur, 12–15 μm (mid tibia) to 28–32 μm long (hind tibia). Basitarsus of mid leg with 3 sensilla chaetica (n = 1).

Hypopygium. Gonostylus straight or slightly curved and directed medially, with parallel margins tapering to widely rounded apex. Anal tergite with 2–4 median setae and small microtrichia-free area surrounding its base. Dark tergite bands of V-type, separated by slightly darker median area of anal tergite. Lateral teeth and basilateral setae absent ( Fig. 4 ). Anal point slender, with distinctly narrowed and elongated tip, apically blunt or transversally cut, armed with 3–5 (usually 4) spinulae placed in row between crests forming a pit ( Figs 15– 18 ); 5–8 lateral setae on each side of anal point ( Fig. 4 ). Superior volsella roundish, slightly elongated and directed medially, with median margin transversely cut, bearing 2 strong anteromedian and 4–8 fine dorsal setae. Digitus stout, extending far beyond superior volsella, strongly bent distally, forming relatively small apical pear-shaped lobe with narrowed conical tip and single seta at its base ( Fig. 21 ). Stem of median volsella strongly reduced, 6–8 μm long, located under superior volsella, bearing group of short lamellae; inner margin of coxite above median volsella slightly concave ( Fig. 24 ). Inferior volsella parallel-sided, tapering to transversally cut apex, bearing darkly pigmented ridge in dorsomedian position ( Fig. 27 ).

Discussion. The presence of the pear-shaped apical lobe of the digitus and the very short median volsella makes Tanytarsus brundini and T. curticornis most similar to T. salmelai . The character best separating Tanytarsus salmelai is the narrowed and strongly elongated tip of the hypopygial anal point ( Figs 15–18 ). The inferior volsella transversally cut apically ( Figs 4 , 27 ), the reduced anal lobe of wing, the brownish wing membrane covered with sparse macrotrichia apically ( Fig. 3 ), the presence of frontal tubercles, the length proportions of the 3rd and 4th palpomere as well as the low AR and LR of all legs (Table) distinguish Tanytarsus salmelai from the two relatives compared.

The enlarged apex of digitus, similar to that found in Tanytarsus salmelai , can also be observed in the Afrotropical Tanytarsus congus and T. pseudocongus . Both species fit the chinyensis group well in having the digitus-seta, and are easily separable based on highly specific hypopygial features, in particular the shape of their anal points and inferior volsellae ( Ekrem 2001).

Although the larval habitat of the new species is not known in any detail, it may be presumed that immatures of Tanytarsus salmelai inhabit eutrophic fens, nowadays rare in Finland. The specimens examined were sampled with a sweep net from fens surrounded by small temporary ponds (all sites) and mossy springs (Aksonjunni). Interestingly enough, no adults were collected with Malaise traps set at the same sites throughout the seasons. A correlation between flying activity of the species and its distinct wing surface reduction needs confirmation. This new species is rare. It was recorded only from three out of hundreds of sites distributed across Lapland and visited for several years.

Figures

FIGURE 4. Tanytarsus salmelai sp. n., male. Hypopygium.

FIGURES 1 – 3. Male wing. 1: Tanytarsus brundini, 2: T. curticornis, 3: T. salmelai sp. n.

FIGURES 5 – 18. Variability in hypopygial anal point. 5 – 9: Tanytarsus brundini, 10 – 14: T. curticornis, 15 – 18: T. salmelai sp. n.

FIGURES 19 – 27. Hypopygial volsellae. 19 – 21: superior volsella and digitus, 22 – 24: median volsella and inner margin of coxite, 25 – 27: inferior volsella. 19, 22, 25: Tanytarsus brundini; 20, 23, 26: T. curticornis; 21, 24, 27: T. salmelai sp. n.