Tanytarsus briani, Reis & Gil-Azevedo & Ferreira-Keppler, 2021

Reis, Patricia Do Rosario, Gil-Azevedo, Leonardo H. & Ferreira-Keppler, Ruth L., 2021, Two new species of Tanytarsus van der Wulp (Diptera: Chironomidae) from Costa Rica, Zootaxa 4966 (1), pp. 84-90 : 85-87

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Tanytarsus briani

sp. nov.

Tanytarsus briani sp. nov.

( Figs. 1A–B View FIGURE 1 , 3A View FIGURE 3 )

Type material. Holotype: adult male, Costa Rica, Prov. San José, Moravia, Zurquí de Moravia (10°02’58” N – 84°00’57” W), Creek 1 north. 1600 m Canopy Malaise trap. 30. iii to 6.iv.2013, ( IN- BIOCRI-COSTA RICA). GoogleMaps

Etymology. Named in honor of Dr. Brian V. Brown, the Principal Investigator of ZADBI project.

Diagnostic characters: The new species can be separated from others by the following combination of characters: Y-shaped anal tergite bands; anal point elongated, with a trifid apex; two pairs of long bars; superior volsella almost sub-rectangular; digitus finger-like, short, pointed, not reaching the margin of the superior volsella; median volsella with simple lamellar setae mounted apically and 4 regular setae; gonostylus short, straight, of almost uniform width from base to apex.

Description. Adult male (n=1). Small, total length 1.80 mm. Wing length 1.24 mm.

Colouration. Head yellowish-brown, flagellum and maxillary palp pale brown. Thorax and legs yellowish. Abdomen yellowish.

Head. Eyes bare, with little dorsomedian extension. Frontal tubercles short, 7.5 µm long. Temporal setae 6, uniserial. Antennae missing. Clypeus with 12 setae. Palpomeres 2–5, lengths (in µm): 30, 100, 65,160.

Thorax. Ac 5, biserial; Pa 1; Scts 6. Halteres with 5 setae on both. Dorsocentral setae (Dc) not observed.

Wing ( Fig. 3A View FIGURE 3 ). Width 0.39 mm. VR 1.24. Sc and M bare, the remaining wing veins and cells setose. Brachiolum without seta.

Legs. Foreleg bearing single tibial spur, 25 μm long. Mid leg tibia bearing two spurs, 30 μm and 40 μm long, and two separated combs. Hind leg tibia bearing two spurs, 27.5 μm and 40 μm long, and two separated combs. Lengths of leg segments and leg ratios as in Table 1 View TABLE 1 .

Hypopygium ( Figs. 1A–B View FIGURE 1 ). Tergite IX 142 μm long, with 2 shorts distal setae. Y-shaped anal tergite bands “fused” on the median part of tergite and reaching anal point, about 34 μm long. Anal point elongated (36 µm long) and slender, lateral margins concave, in the dorsal aspect apex with three rounded portions, ventromedian projection longer than the length of the anal point, lateral margin bearing 3 distal setae; AnPR 3.60. Two pairs of anal point bars, not surpassing the apex of anal point; AnPBR 2.00. Superior volsella sub rectangular, elongated (32 µm long), with 4 setae on dorsal surface and 2 setae on anteromedian margin (one dorsal, one ventral), posteromedian corner elongated and rounded; digitus 11 µm long, pointed, finger-like, not extending beyond margin of superior volsella. Stem of median volsella about 12 μm long, with simple lamellar setae mounted apically and 4 regular setae. Inferior volsella ca. 71 μm long, S-shaped, apex with a prominent triangular swelling. Gonocoxite 67μm long. Gonostylus short (51 μm long), straight, of almost uniform width from base to apex, rounded tip. HR 1.41.

Remarks. The anal point and the gonostylus are the main characters that differentiate the male T. briani sp. nov. from other species. In the identification key for the males of Tanytarus ortoni species group, the shape of the anal point of T. briani is similar to the species Tanytarsus yara and Tanytarsus castelnaui . The trifid apex, in dorsal aspect, of the anal point is similar to what is observed in T. yara ; the ventromedian projection of the anal point is similar to that of T. castelnaui . However, T. briani can be easily distinguished from the two above mentioned species by the presence of two pairs of long anal bars in contrast to a pair of short anal bars found in T. yara and T. castelnaui . The small gonostylus, of almost uniform width, does not correspond to any species of Tanytarus ortoni species group, this format apparently being unique among the Neotropical species of Tanytarsus .

Distribution and ecological notes. Tanytarsus briani was collected at an elevation of about 1,600 meters, demonstrating the wide adaptive range of chironomids of the Tanytarsini tribe, as almost all species of the Tanytarsus ortoni species group have been recorded from lowland areas of tropical climate.