Tanytarsus jacaretingensis, Sanseverino & Fittkau, 2006

Sanseverino, Angela M. & Fittkau, Ernst Josef, 2006, Four new species of Tanytarsus van der Wulp, 1874 (Diptera: Chironomidae) from South America, Zootaxa 1162, pp. 1-18 : 13-16

Tanytarsus jacaretingensis sp. nov.

( Figs. 17–21 )

Type material: Holotype: 1 adult male, slide­mounted in Euparal. BRAZIL, Amazonas State, lower Rio Solimões, Lago Jacaretinga , collected on river bank (reared), 24.xii.1971, F. Reiss ( INPA) . Paratypes: 6 adult males as holotype except 28.xii.1971 ( ZSM) ; 1 adult male, as holotype except 11.i.1972 ( ZSM) ; 1 adult male together with 2 pupal exuviae on same slide, as holotype except 12.i.1972 ( ZSM) ; 1 adult male, BRAZIL, São Paulo State, São Carlos, Fazenda Canchim (EMBRAPA), Represa da Colônia (reservoir), 12.ii.2001, S. Trivinho Strixino (UFSCar) ; 1 adult male as previous except 17.ii.2001 (UFSCar); 1 adult male, slide­mounted in Euparal, FRENCH GUYANA, Mana , swamp, 29.xii.2002, M. Kotrba ( ZSM) .

Etymology: Tanytarsus jacaretingensis is named after its type locality, Lake Jacaretinga.

Diagnostic characters

Tanytarsus jacaretingensis can be separated from other males of Tanytarsus by the following combination of characters: Antennal ratio 1.02–1.25; eye without dorsomedian extension; frontal tubercle large; median tubercle on scutum present, small and rounded; wing with few setae, wing veins Sc, R 1, M, M 3+4, Cu, false vein (close to Cu and M 3+4), Cu 1, Postcubitus and An bare, wing cells m, m 3+4, cu and an bare; tergite IX with comparatively large microtrichia­free areas to each side of the anal point; anal tergal bands of Y­type ending well anterior to the base of the anal point; anal point elongate with rounded tip, with 1 or rarely 2 spines between well­developed anal crests; microtrichia between crests absent; superior volsella rugose, without microtrichia, with wrinkles and rugosities on median, lateral and posterior margins, lateral margin with wrinkled flap­like projection, anteromedian portion quite projected; digitus small; median volsella with pectinate lamellae, not reaching apex of inferior volsella; inferior volsella slender, straight, distal part slightly swollen with rounded apex; gonostylus elongate, curved, stout, tapering towards apex.

Male (n = 6)

Head. AR 1.08–1.19 (mean 1.12). Antennal flagellomeres one to twelve 421–460 µm long, thirteen 465–550 µm long. Eye without dorsomedian extension; frontal tubercle large, 16–20 µm long, about 3 times as long as wide; with 9–10 temporal setae; clypeus with 10–13 setae; lengths of palpomeres (in µm): 24–30, 32–40, 74–88, 79–94, 130–154.

Thorax. Length 738–840 µm. Scutal tubercle present, small and rounded; 6–7 dorsocentrals, 2–5 acrostichals, 1 prealar, 4 scutellars. Haltere with 4–5 setae.

Wing. Length 1330–1553 µm, width 398–430 µm; L/WR 3.34–3.61. Brachiolum with 1 seta, Sc bare, R with 1–4 setae, R 1 bare, R 4+5 with 2–3 setae, M bare, M 1+2 with 6–17 setae, M 3+4, Cu, Cu 1, PCu and An bare. Cell m and false vein bare, r 4+5 with 19–35 setae, m 1+2 with 1–7 setae, false vein bare, m 3+4, cu and an bare.

Legs. Foreleg bearing single tibial spur, 22–26 µm long. Combs of mid tibia 11–14 µm wide with 21–22 µm long spur, and 12–14 µm wide with 23–26 µm long spur; combs of hind tibia 13–15 µm wide with 24–28 µm long spur, and 14–16 µm wide with 26–32 µm long spur. Lengths of leg segments (in µm) and leg ratios as in Table 3.

Abdomen. Length 1710–2060 µm.

Hypopygium ( Fig. 17 ). Tergite IX 114–124 µm long, with 4–8 median setae placed from well anterior to more or less close to the base of the anal point, with 12–14 apical setae and microtrichia­free areas on each side of the base of the anal point; lateral tooth absent. Orolateral spine of laterosternite IX difficult to observe, probably absent. Anal tergal bands of Y­type, confluent in median part of tergite, not reaching anal point. Anal point 51–54 µm long, elongate with rounded tip ( Figs. 18­19 ), with pair of well­developed anal crests, 22–25 µm long, not extending posterior to tergite IX; posterior part of anal point dorsally sclerotized; microtrichia absent between crests; 1 or rarely 2 spines between anal crests. Superior volsella as in Fig. 20 , without microtrichia, median, lateral and posterior margins with wrinkles and rugosities; anteromedian portion projected, posteromedian part elongate and wrinkled, lateral margin with wrinkled flap­like projection; dorsal surface with 4–6 setae, 1 seta on anteromedian projection, 1 seta on median margin and 1 seta on well­developed ventral tubercle on anteromedian margin. Longitudinal axes of superior volsella and body at angle of 30–34. Digitus small. Median volsella 10–14 µm long with 15–22 µm long simple setae and 16–18 µm long pectinate lamellae ( Fig. 21 ), not reaching apex of inferior volsella. Inferior volsella 69–82 µm long, slender, straight, distal part slightly swollen with rounded apex. Gonocoxite 98–118 µm long; gonostylus 100–120 µm long, curved, stout, tapering towards apex; hypopygium ratio 0.96–1.02.

Discussion

Tanytarsus jacaretingensis appears to be related to the Neotropical T. monospinosus Ekrem & Reiss, 1999 . The males of both species have many characters in common such as large frontal tubercles, almost bare wings, anal tergal bands of Y­type, an elongate and blunt anal point without microtrichia and with one single spine between anal crests ( Figs. 17–19 ), a peculiar superior volsella with wrinkles, rugosities and a flap­like wrinkled projection ( Fig. 20 ), a small digitus, and similar shaped inferior volsella and gonostylus ( Fig. 17 ). Further, while all other described Neotropical Tanytarsus species have eyes with dorsomedian elongation, both T. monospinosus and T. jacaretingensis lack eye elongation. Tanytarsus jacaretingensis differs from T. monospinosus by the presence of a scutal tubercle, by having median volsella, which is reduced in T. monospinosus , presence of acrostichals, which is lacking in T. monospinosus , and by lacking long anteromedian anal tergite setae, while T. monospinosus has 4–6 very long median setae placed anterior on the anal tergite in addition to the usual median setae.

Tanytarsus jacaretingensis is the only Neotropical Tanytarsus species with a scutal tubercle. In Cranston et al. (1989) the genus Tanytarsus is diagnosed without scutal tubercle. However, according to Stur and Ekrem (2000) and Ekrem (2001) both Tanytarsus luctuosus Freeman, 1958 and T. elisabethae Ekrem, 2001 have a scutal tubercle, and Stur and Ekrem (2000) emended the generic diagnosis to also include species with scutal tubercle.

Distribution

Tanytarsus jacaretingensis is recorded from Brazil and French Guyana. In Brazil the species was found in Lake Jacaretinga in the Amazonas State, and in a reservoir in the São Paulo State. Lake Jacaretinga is a “Várzea”, a whitewater floodplain lake, located in a floodplain area in Central Amazon. In French Guyana the species was collected in a swampy area in Mana. Like its close relative T. monospinosus , T. jacaretingensis seems to prefer lentic and flooded areas.

Figures

FIGURES 17–21. Tanytarsus jacaretingensis sp. nov., adult male. 17. Hypopygium, dorsal view. 18. Anal point, lateral view. 19. Anal point, dorsal view. 20. Superior volsella. 21. Median volsella.