Tanytarsus cotopaxi, Giłka, Wojciech & Zakrzewska, Marta, 2013

Giłka, Wojciech & Zakrzewska, Marta, 2013, A contribution to the systematics of Neotropical Tanytarsus van der Wulp: first descriptions from Ecuador (Diptera: Chironomidae: Tanytarsini), Zootaxa 3619 (4), pp. 453-459 : 456-459

Tanytarsus cotopaxi sp. nov.

Type material. Holotype, adult male: ECUADOR, Pichincha province, San Miguel de Los Bancos (canton), Mindo, c. 1400 m a.s.l., 16 September 1999, netting, leg. Dawid Graczyk.

Derivation of the name. The specific name is referred to the Cotopaxi , the biggest volcano in the Pichincha province where the specimen was collected. The name should be treated as a noun in apposition.

Diagnosis. AR low, 0.48. Hypopygium with bristle-shaped median setae; lateral teeth absent; anal point expanded in proximal part, with spinulae arranged in regular row; microtrichia between crests absent; superior volsella ellipse-shaped, deeply excavated at apex, with small field of microtrichia at base; digitus long, with swollen roundish apex; inferior volsella parallel-sided, tapering to round apex; median volsella with setiform and pectinate lamellae.

Description. Adult male (n = 1)

Wing length 1.47 mm.

Colouration. Eyes black; antennal pedicel, head capsule, ground colour of thorax, scutellum, haltere, proximal parts of legs and abdomen greenish yellow; wing membrane with pale greenish undertone; remaining body parts slightly darker, brownish.

Head. Antenna with 13 flagellomeres; AR 0.48. Frontal tubercles absent. Length of palpomeres II–V (μm): 38, 94, 101, 179. Clypeus with 15 setae.

Thorax chaetotaxy. Ac 15; Dc 8 on each side; Pa 1 on each side; Scts 4, outermost pair minute.

Wing. Fig. 2 A. Membrane below R and An with sparse macrotrichia only in distal part, cells r4+5, m1+2 and distal half of m3+4 covered with dense macrotrichia.

Legs. Fore tibia with straight slender spur. Tibial combs of mid and hind leg separated; spurs of mid leg unequal: one long and straight and the second short, tooth-like; spurs of hind leg equal, long and slightly bent. Basitarsus of mid leg bearing 4 hook-shaped sensilla chaetica. Length of leg segments and leg ratios in Table 2 .

Hypopygium ( Fig. 2 B, C). Gonostylus 100 μm long, slightly swollen in proximal part, tapering to slender tip. Anal tergite with 4 bristle-shaped median setae arranged in transversal row. Anal tergite bands of V-type, separated, with distal sections bent and parallelly tapering to the centre of anal tergite; lateral teeth absent. Anal point stout and long, slightly expanded in proximal part, roundish, with abruptly narrowed tip, apically blunt with 3–4 lateral setae on each side and 4 spinulae arranged in regular row and placed in pit framed by semicircular anal crests; entire area surrounding base of anal point covered with microtrichia, microtrichia between crests absent. Superior volsella ellipse-shaped, deeply excavated at apex, with small field of microtrichia at base, bearing 2 dorsal setae, 2 anteromedian setae and small tubercle (seta apparently broken) at base of digitus. Digitus straight and long, extending far beyond superior volsella, with swollen roundish apex. Inferior volsella parallel-sided, tapering to round apex, with slight dorsomedian ridge ( Fig. 2 B). Stem of median volsella 12 μm long, slightly curved, bearing 1 short setiform and 3 slender pectinate lamellae ( Fig. 2 C).

Discussion. We recognized Tanytarsus cotopaxi as a member of the riopreto species group that was so far known from four species (Fittkau & Reiss 1973, Sanseverino 2006). Following the inclusion of T. cotopaxi into the group, we propose to delimit the recently emended group diagnosis (Sanseverino 2006) to several principal characters as follows: LR1 relatively high (c. 2.9–3.9); anal tergite bands parallelly tapering to the centre of anal tergite, ending close to anal point base; median setae strong or bristle-shaped; anal point elongate, with crests and spinulae well developed; superior volsella heart-shaped, ellipse-shaped or somewhat T-like, distinctly concave or excavated; two setae on median margin of superior volsella and single seta-bearing tubercle at base of digitus; digitus extending beyond superior volsella; median volsella with setiform and pectinate lamellae; stem of median volsella and digitus more or less of the same length. The riopreto group appears to be closely related to the Holarctic chinyensis group, as suggested by Giłka and Paasivirta (2009). The median volsella / digitus proportions and the size of median setae are the best diagnostic characters for separation of the two groups.

The adult male of Tanytarsus cotopaxi is easily determinable by the low AR (0.48 vs. 0.6–1.0 known in the riopreto group so far), the bristle-shaped median setae arranged in transversal row, the anal point distinctly expanded in proximal part, bearing large spinulae placed in row, the superior volsella ellipse-shaped, deeply excavated at apex, the digitus long, with swollen apex, and the median volsella with single setiform and three pectinate lamellae. The field of microtrichia on the superior volsella found in T. cotopaxi is known in the group only from T. cururui Fittkau et Reiss.

Tanytarsus curvicristatus Contreras-Lichtenberg, 1988

Tanytarsus curvicristatus Contreras-Lichtenberg, 1988: 101 (adult male; figs 1, 2; Colombia); Sanseverino 2006: 198 (adult male, fig. 62, Peru); Sanseverino & Trivinho-Strixino 2010: 74.

Material examined. ECUADOR, Pichincha province, San Miguel de Los Bancos (canton), Mindo, c. 1400 m a.s.l., 25–31 August 1999, netting, 1 male, leg. Dawid Graczyk.

Discussion. Most of diagnostic characters found in the examined specimen of Tanytarsus curvicristatus are consistent with those originally described and recently complemented (Contreras-Lichtenberg 1988, Sanseverino 2006). The adult male of the species can be identified by the following feature combination: wing covered with macrotrichia only in distal part: sparse macrotrichia in 2/3 distal area of r4+5, m1+2 and along wing margin in cubital and anal cells ( Fig. 3 A); hypopygial anal point with pair of short and broad oval crests above round pit, and with two bars ( Fig. 3 B); superior volsella round at base, with protruding posteromedian corner ( Fig. 3 C); digitus vestigial, pointed; median volsella short, with setiform, slender spindle-shaped and several ramose lamellae ( Fig. 3 D). Other metric and meristic diagnostic characters presently complemented: frontal tubercles absent, AR 0.56, 12 clypeals, 7–8 dorsocentrals, 4–5 scutellars and 1 prealar seta; tibial spur of fore leg 24 μm long, combs of mid and hind legs 12–20 μm long, spurs 24 and 40 μm long (mid leg), 32 and 44 μm long (hind leg); LR2 0.61, LR3 0.64; gonostylus c. 95 μm long, stem of median volsella 8 μm long. In proportion to the smaller size, the individual examined shows a distinctly shorter wing (1.25 mm vs. 1.33–2.30 mm), antennal and palp segments and a slightly higher LR1 (2.5 vs. 2.4) (cf. l.c.).

The systematic position of several Tanytarsus species having the characteristic structure of the anal point ( Fig. 3 B) is discussed in detail by Sanseverino and Trivinho-Strixino (2010).

Acknowledgements

We thank the legator, Mr Dawid Graczyk of Gdynia, Poland, Dr. Angela M. Sanseverino (Universidade Federal do Rio de Janeiro, Brazil), for supplying information on Neotropical Tanytarsus . Thanks are directed to Dr. Diego A. Añón Suárez (Centro Regional Universitario Bariloche, Argentina) and Dr. Mariano Donato (Museo de La Plata, Argentina) who kindly agreed to evaluate the manuscript.

References

Contreras-Lichtenberg, R. (1988) Tanytarsus curvicristatus spec. nov. eine neue Chironomidenart aus Kolumbien (Diptera: Chironomidae). Spixiana, supplement 14, 101 –104.

Ekrem, T. & Reiss, F. (1999) Two new Tanytarsus species (Diptera: Chironomidae) from Brazil, with reduced median volsella. Aquatic Insects, 21, 205 –213. http://dx.doi.org/10.1076/aqin.21.3.205.4525

Fittkau, E.J. & Reiss, F. (1973) Amazonische Tanytarsini (Chironomidae, Diptera) I. Die riopreto -Gruppe der Gattung Tanytarsus. Studies on the Neotropical Fauna, 8, 1–16. http://dx.doi.org/10.1080/01650527309360451

Giłka, W. (2008) A rapid technique of producing spatial colour illustrations of diagnostic structures in small dipterans. Dipteron, Bulletin of the Dipterological Section of the Polish Entomological Society, 24, 8–10.

Giłka, W. & Paasivirta, L. (2009) Evaluation of diagnostic characters of the Tanytarsus chinyensis group (Diptera: Chironomidae), with description of a new species from Lapland. Zootaxa, 2197, 31–42.

Prat, N. & Rieradevall, M. (2011) Guia para el reconocimiento de las larvas de chironomidae (Diptera) de los ríos altoandinos de Ecuador y Perú. Clave par la determinación de los géneros. Departamento de Ecología, Universidad de Barcelona. Proyectos de invetigación CERA, FUCARA y BIQURA. Con el auspicio de la AECID y el MCYT de España, 78 pp. Available online: http://www.ub.edu/riosandes / (accessed: November 2012).

Reiss, F. (1972) Die Tanytarsini (Chironomidae, Diptera) Südchiles und Westpatagoniens. Mit Hinweisen auf die Tanytarsini - Fauna der Neotropis. Studies on the Neotropical Fauna, 7, 49–94. http://dx.doi.org/10.1080/01650527209360434

Saether, O.A. (1980) Glossary of chironomid morphology terminology (Diptera: Chironomidae). Entomologica scandinavica, supplement 14, 1–51.

Sanseverino, A.M. (2006) A review of the genus Tanytarsus van der Wulp, 1874 (Insecta, Diptera, Chironomidae) from the Neotropical Region. Dissertation in: Ludwig-Maximilians-Universität München, Fakultät für Biologie, 312 pp. Available online: http://edoc.ub.uni-muenchen.de/4975 (accessed: Feb. 2009).

Sanseverino, A.M., Fittkau E.J. (2006) Four new species of Tanytarsus van der Wulp, 1874 (Diptera: Chironomidae) from South America. Zootaxa, 1162, 1–18.

Sanseverino, A.M., Trivinho-Strixino, S. (2010) New Species of Tanytarsus van der Wulp (Diptera: Chironomidae) from São Paulo State, Brazil. Neotropical Entomology, 39, 67–82. http://dx.doi.org/10.1590/S1519-566X2010000100010

Trivinho-Strixino, S. & Strixino, G. (2004) Two new species of Tanytarsus from southeast of Brazil (Insecta, Diptera, Chironomidae). Spixiana, 27, 155 –164.

Wirth, W.W. & Marston, N. (1968) A method for mounting small insects on microscope slides in Canada balsam. Annals of the Entomological Society of America, 61, 783 –784.

Figures

FIGURE 2. Tanytarsus cotopaxi sp. nov., adult male. A—wing, B—hypopygium, C—median volsella (magnified x 2 relative to hypopygium).

FIGURE 3. Tanytarsus curvicristatus Contreras-Lichtenberg, 1988, adult male. A—wing, B—hypopygial anal point, C—superior volsellae, D—median volsellae. AC—anal crests, Ba—anal point bar.

Tables

TABLE 2. Lengths (μm) of leg segments and leg ratios of male Tanytarsus cotopaxi sp. nov.

fe	ti	ta1	ta2	ta3	ta4	ta5	LR
P1 840	380	1270	565	445	355	150	3.34
P2 795	605	435	195	140	80	55	0.72
P3 820	745	–	–	–	–	–	–