Tanytarsus patagonicus ( Reiss, 1972 ) Reiss, 1972

Sanseverino, Angela M., Trivinho-Strixino, Susana & Nessimian, Jorge L., 2010, Taxonomic status of Nimbocera Reiss, 1972, a junior synonym of Tanytarsus van der Wulp, 1874 (Diptera: Chironomidae), Zootaxa 2359, pp. 43-57 : 44-49

Tanytarsus patagonicus ( Reiss, 1972) comb. n.

( Figs 1–15 )

Type material. Holotype: 1 adult male, South Chile, Puerto Natales, Province of Magallanes, Laguna Diana, shore ponds, 2.I.1970, slide mounted in Euparal, leg. F. Reiss ( NHRS). Paratypes: 4 adult males, same as holotype except deposited at ZSM; 4 pupal exuviae, same as holotype except deposited at ZSM; 2 pharate males as holotype except deposited at ZSM; 1 pharate male, South Chile, Lago Villarrica, 3.XI.1969, slide mounted in Euparal, leg. F. Reiss; 2 pupal exuviae, Lago Pellaifa, drift, 5.XII.1953, slides mounted in Euparal, leg. L. Brundin; 3 adult males, Argentina, Bariloche, Laguna Trebol (shallow littoral lake), 17.XI.1969, slides mounted in Euparal, leg. F. Reiss; 2 pupal exuviae as previous (all paratypes at ZSM).

Additional material examined: 1 adult male, Chile, 21.8.1970, slide mounted in Euparal; 1 pharate male, South Chile, Puerto Natales, Province of Magallanes, Laguna Diana, shore pond, 1. I.1970, slide mounted in Euparal, leg. F. Reiss; 1 adult male as previous (all material deposited at ZSM).

Diagnosis. Male Imago: Antenna short (brachycerous), plume reduced; low AR; palp reduced; wing somewhat reduced and cuneate, wing vein R2+3 distinct; wings with few setae, all wing setae shorter than those observed in Neotropical Tanytarsus ; tarsomere 4 of mid leg cordiform; tergite IX without median setae; anal tergal bands separate, curved, ending “almost together” on the middle of tergite; anal point with pair of weakly developed, low anal crests; with field of microtrichia on entire surface between the crests; spines absent, 5–7 short setae between anal crests; superior volsella circular, posteromedian margin well projecting and thumb-like, without microtrichia; digitus short and rounded; median volsella with ramose lamellae; gonostylus large, thick and curved inwards, distally rounded.

Pupa: Frontal setae thin and short, cephalic tubercles weakly developed; wing sheath without nose, prealar tubercle rectangular; thoracic horn thin, with small, weakly sclerotized spines; three precorneals not in triangular pattern, placed on a tubercle; tergite II with homogeneous shagreen, interrupted/ sparse medially; T III with pair of long bands of longer spines on posterior half of tergite, bands curving outward; T IV with bracket-shaped pair of long bands of longer spines directed to caudal, median and oral; T V and T VI with elongate spine patches; T VIII–IX with fine oral-lateral shagreen; posterolateral comb of segment VIII with 4–6 stronger marginal teeth and 12–17 smaller ones on pad; abdominal segment I without lateral seta; segments II–VII with 3 lateral setae; segment VIII with 4 lateral taeniae, 2 dorsal setae and 1 ventral seta and 1 ventral taenia.

Larva: Antennal pedestal with rounded, wrinkled spur, segment 2 of antenna with narrow, not sclerotized ring near base; AR 1.82; Lauterborn organs small, 3–4 µm long, situated on apex of very long and slim pedicels, pedicels annulated for more than 4/5 of their length; mentum with eleven brown to dark brown teeth, median tooth trifid; mandible with dorsal pale tooth, apical tooth and 4 inner teeth brown to dark brown; clypeal seta S3 unequally bifid.

Emendations to previous diagnoses: The eyes of Tanytarsus patagonicus adult males have small dorsomedian extensions ( Cranston et al. (1989) list this as absent), the thorax has 1 prealar (in Cranston et al. (1989) prealars are absent) and the wing vein R2+3 is "fused" with R4+5 along 2/3 of its length basally, ending midway between apices of R1 and R4+5.

Description. Male Imago (n = 6)

Head ( Figs 1–2 ). AR 0.45–0.53. Antenna short (brachycerous) and more or less curved, plume reduced. Antennal flagellomeres one to twelve 400–428 µm long, thirteen 188–197 µm long, total length 588–625 µm. Eyes with dorsomedian extension; large frontal tubercles (length 18–22 µm), about 2.5 times as long as wide; 9–10 temporal setae; clypeus with 20–24 setae; lengths of palpomeres (in µm): 35–37, 38–40, 58–66, 60–61, 68–72, total length 259–276 µm.

Thorax. Length 892–1000 µm. Scutal tubercle absent; 7–8 dorsocentrals, 8–12 acrostichals, 1 prealar, 4– 6 scutellars. Haltere with 4–5 setae.

Wing. Weak brachyptery, length 1500–1700 µm, width about 640 µm; L/WR about 2.53. Brachiolum with 1 seta, Sc bare, R with 14 setae, R1 with 9 setae, R2+3 distinct, bare, ending midway between apices of R1 and R4+5, R4+5 with 10 setae, M bare, M1+2 with 14 setae, M3+4, Cu, Cu1 and Postcubitus bare, An with 2 setae. Cell m and false vein bare, r4+5 with 42 setae, m1+2 with 32 setae (false vein bare), m3+4 with 5 setae, cu and an bare.

Legs ( Figs 3–6 ). Fore tibia without spur (in the original description with small scales distal frayed), mid tibia with pair of small, separated combs (12 µm long), only 1 comb with spur, hind tibia with 2 separated combs (12 µm long) without spur, according to Cranston et al. (1989) occasionally 1 spur is present. Tarsomeres of mid (principally) and hind leg shorter, tarsomere 4 of mid leg cordiform. Lengths of leg segments and leg ratios as in table 1.

fe ti ta1 ta2 ta3 ta4 ta5 LR BV SV p1 800–815 518–580 *670–700 310–330 268–295 240–255 150–165 1.20–1.29 2.00–2.05 1.96–1.99 p2 667–700 510–560 150–165 90–100 70–90 51–60 68–75 0.29 4.38–4.75 7.63–7.84 p3 800–840 660–700 260–280 160–185 168–190 92–100 91–100 0.39–0.40 3.16–3.36 5.50–5.61 *In the original description the length of tarsomere 1 of fore leg is 435 µm.

Abdomen. Length 2340–3140 µm.

Hypopygium ( Figs 7–10 ). Tergite IX 172–200 µm long, without median setae and with 28–32 apical setae, lateral tooth absent. T IX with microtrichia-free areas on each side of anal point. Orolateral spine of laterosternite IX present, 4–5 µm long. Anal tergal bands separate, curved, running parallel and ending “somewhat together” on the middle of tergite, more or less close to anal point. Anal point 57–70 µm long, elongate with rounded tip, with pair of weakly developed, low anal crests (29–37 µm long) not extending posterior to tergite IX; with field of microtrichia on entire surface between the crests; spines absent, 5–7 shorter setae between anal crests. Superior volsella oval, posteromedian margin well projecting and thumblike, without microtrichia; anterior, median, lateral and posterior margins curved; 13–14 setae on dorsal surface, 1–2 setae proximal on projection of posteromedian margin, 4 setae on median margin (1–2 dorsal, 2– 3 ventral) and 1 seta ventral, close to anterior margin. Longitudinal axes of superior volsella and body at angle of 36–40°. Digitus short and blunt, not reaching median margin of superior volsella. Median volsella 22–27 µm long with 18–25 µm long simple lamellae and 32–40 µm long ramose lamellae, not reaching apex of inferior volsella. Inferior volsella 150–153 µm long elongate and thick, expanded in distal half, area carrying setae with moderately large dorsoapical swelling. Gonocoxite length 148–155 µm; gonostylus 185–198 µm, large, thick and curved inwards, distally rounded; hypopygium ratio (HR) 0.77–0.82.

Pupa (n=5)

Total length 3840–4510 µm long.

Pupal exuviae pale brown, thorax and lateral muscle marks somewhat brownish.

Cephalothorax ( Figs 11–13 ). Frontal apotome smooth, with wrinkles on area of cephalic tubercles. Frontal setae thin and short, 50–62 µm long, mounted apical on weakly developed cephalic tubercles; frontal warts absent. Pedicel sheath tubercle well developed. Thorax smooth, 1040–1100 µm long, with points along median suture; a small, rounded tubercle is present anteriorly near median antepronotal. Thoracic horn thin, 292–373 µm long, with small, weakly sclerotized spines. Wing sheath without nose, prealar tubercle well developed, rectangular. Three precorneals in row, apparently placed on a tubercle, another small tubercle is present close to Pc3. Anterior precorneal stronger (100–125 µm), Pc2 (85–102 µm) and Pc3 (92–110 µm) closer to each other; 1 median (100–115 µm) and 2 lateral antepronotals (4–5 µm and 62–79 µm, the latter one difficult to measure, appearing to be broken in most of the specimens); 2 pairs of dorsocentrals, anterior pair 73–100 µm (thin) and 42–53 µm (thick), posterior pair 68–76 µm (thin) and 110–120 (thick), the latter one stronger than other three.

Abdomen ( Figs 14–15 ). Total length 2800–3420 µm. Tergites I and VII without armament. T II with homogeneous shagreen, interrupted/ sparse medially. T III with pair of long bands of longer spines placed on posterior half of tergite, bands curved outward. T IV with bracket-shaped pair of long bands of longer spines directed to caudal, median and oral. T V and T VI with elongate spine patches. T VIII–IX with fine orallateral shagreen. Sternites I, IV–VII without armament. S II–III with very fine oral-lateral shagreen. S VIII with fine oral-lateral shagreen. Conjunctives and pleura unarmed. Hook row 204–260 µm, about 1/2 width of tergite II. Pedes spurii A absent; pedes spurii B present on segment II. Posterolateral comb of segment VIII 60 –76 µm wide, with 4–6 strong marginal teeth and 12–17 smaller ones on pad. Abdominal setation: segment I with 3 D, the most anterior longer, 0 L and 0 V; segment II with 4 D, 3 L and 4 V; segments III–VII with 5 D, 3 L and 5 V; segment VIII with 2 D, 4 lateral taeniae and 1 V and 1 ventral taenia. Anal lobe well developed, with fringe of 17–20 taeniae in single row and with two pairs of dorsal taeniae. Tergites II–VIII with O-setae.

Distribution and ecological notes. Tanytarsus patagonicus is recorded from southern Chile and Argentina (Patagonia). Larvae and pupae inhabit ponds, lakes and coastal lagoons. According to Reiss (1972), the larvae probably prefer to inhabit nutrient-rich sediments of standing waters, where mass-developments can occur. Since adults were never trapped at the surrounding vegetation of the corresponding water-body, Reiss (1972) presumed that the brachypterous males do not form swarms and the mating probably takes place on water surface.

Figures

FIGURES 1 – 6. Tanytarsus patagonicus (Reiss), adult male. 1. Head. 2. Frontal tubercle. 3. Mid leg, cordiform tarsomere 4 marked by arrow. 4. Hind leg. 5. Comb of mid tibia. 6. Comb of hind tibia.

FIGURES 7 – 10. Tanytarsus patagonicus (Reiss), adult male. 7. Hypopygium, dorsal view. 8. Anal point, lateral view. 9. Superior volsella and digitus, variation. 10. Median volsella.

FIGURES 11 – 15. Tanytarsus patagonicus (Reiss), pupa. 11. Frontal apotome. 12. Thorax. 13. Thoracic horn. 14. Abdomen, dorsal view; dorsal setae of segments II – VII not drawn. 15. Posterolateral comb of abdominal segment VIII.