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Revista de la Sociedad Entomológica Argentina

versión impresa ISSN 0373-5680

Rev. Soc. Entomol. Argent. vol.73 no.3-4 La Plata dic. 2014



Review of taxonomic status of Polypedilum quinquesetosum (Edwards, 1931) (Diptera, Chironomidae)

Estatus taxonómico de Polypedilum quinquesetosum (Edwards, 1931) (Diptera, Chironomidae)


Fuentes, María C. & Mariano Donato

Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA), (CONICET - CCT La Plata), (FCNyM, UNLP), 122 and 60, La Plata, 1900, Buenos Aires, Argentina. E-mail:;

Recibido: 14-V-2014;
Aceptado: 30-VIII-2014


RESUMEN. El estado taxonómico de Polypedilum quinquesetosum (Edwards) es revisado sobre la base del estudio del holotipo macho de la especie y de nuevos hallazgos. Tras el análisis de caracteres, esta especie pertenece al subgénero Tripodura Townes y se establece la nueva combinación. Se expande la diagnosis de la especie, se discute las relaciones con el resto de las especies Neotropicales del subgénero y se extiende su distribución geográfica.

PALABRAS CLAVE: Polypedilum; Chironominae; Sistemática; Somuncurá; Neotrópico.

ABSTRACT. The taxonomic status of Polypedilum quinquesetosum (Edwards) is reviewed upon the study of the male holotype of the species and new findings. After the character analysis, this species belongs to the subgenus Tripodura Townes and the new combination is established. The species diagnosis is expanded, the relationships with the rest of the Neotropical species of the subgenus are discussed and its geographical distribution is extended.

KEY WORDS: Polypedilum; Chironominae; Systematics; Somuncurá; Neotropics.



The genus Polypedilum Kieffer (Chironominae, Chironomini) is a cosmopolitan genus, occurring in all zoogeographical regions except Antarctica. Polypedilum is a very species-rich genus of chironomids and the larvae occur in all standing and flowing waters, except at high altitude and latitude (Vårdal et al., 2002). The genus is quite well known in the Neotropics (Spies & Reiss, 1996) with more than 65 described species.

The genus Polypedilum has been divided into five subgenera: Cerobregma Sæther & Sundal; Pentapedilum Kieffer; Polypedilum s. str., with two species groups, the nubeculosum and the nubifer groups; Tripodura Townes; and Uresipedilum Sasa & Kikuchi (Sæther & Sundal, 1999). The genus Asheum Sublette & Sublette (Sublette & Sublette, 1983) was previously placed in Polypedilum, but as the pulvilli are not bilobed and the eighth abdominal segment of the male is not basally constricted it was reestablished as a separate genus by Oyewo & Sæther (2008). Sæther et al. (2010) reestablished Tripedilum Kieffer and Kribionympha Kieffer genera as subgenera of Polypedilum and erected the subgenus Probolum Andersen & Sæther.

Edwards (1931) described the species Chironomus (Polypedilum) quinquesetosus that was later transferred to the genus Polypedilum by Spies & Reiss (1996). This species is only known by its type material from Peulla and Ensenada in Chile and Correntoso Lake in Argentina. The finding of male imagos of Polypedilum quinquesetosum collected during several field trips allows the review of its taxonomic status and the proposal of a new combination, the expansion of its diagnosis and the extension of its geographical distribution.


The specimens were mounted in Canada balsam following the procedures described by Paggi (2009) and were compared with the holotype deposited in the Natural History Museum (London, UK (NHM)). The holotype of Polypedilum quinquesetosum is pinned and the hypopygium is mounted in Canada balsam, for this reason its measurements were not included in the diagnosis presented in this study. Measurements are in μm except when otherwise stated. The terminology and abbreviations for general morphology follow Sæther (1980). The new material of Polypedilum quinquesetosum is deposited in the Museo de La Plata, Buenos Aires (MLP).


The species P. quinquesetosum belongs to the subgenus Tripodura for its club-shaped superior volsella without an apical projection, a broad anal point, superior volsella covered with microtrichia and with setae on distal parts of the outer and inner margin, but the wings lack dark markings and the wing membrane lacks setae. The new combination Polypedilum (Tripodura) quinquesetosum com. nov. is established.

Polypedilum (Tripodura) quinquesetosum (Edwards, 1931) com. nov.

Chironomus (Polypedilum) quinquesetosus Edwards, 1931: 315.
Polypedilum quinquesetosum, Spies & Reiss, 1996: 72.
Polypedilum (Tripodura) quinquesetosum, new combination.

Material examined. CHILE: Llanquihue province, Peulla, 12/13-XII-1926, F. & M. Edwards, B.M. 1927-63, holotype male (NHM).

ARGENTINA. Neuquén: P. N. Nahuel Huapi, Lago Traful, Villa Traful, 40° 30' 16.5'' S, 71° 34' 57.2'' W, 11-II-2002, sweep net, Donato col, 1 male (MLP); Río Negro: P. N. Nahuel Huapi, A° Challhuaco, 41° 13' 32.9'' S, 71° 17' 49.8'' W, 1045 m, 28-II-2007, drift net, Garré and Montes de Oca col., 1 male (MLP); P. N. Nahuel Huapi, A° Blest, 41° 01' 24.8'' S, 71° 49' 21'' W, 790 m, 3-III-2007, CDC, Garré and Montes de Oca col., 2 males (MLP); P. N. Nahuel Huapi, Laguna Los Juncos, 41° 03' 37.9'' S, 71° 00' 34.3'' W, 906 m, 12-XII-2006, sweep net, Garré and Montes de Oca col., 3 males (MLP); P. N. Nahuel Huapi, Puerto Blest, 20-II-2008, at light, Donato col., 1 male (MLP); Vertiente y chorrillo, Estancia Jaguar Musso, Paraje Chasicó, 41° 08' 28'' S - 67° 35' 43.9'' W, 961 m, 6/7-XI-2006, sweep net, Donato col., 2 males (MLP).

Male (n = 10). Total length 3.38-4.98 mm. Wing length 1.72-2.19 mm. Wing length / length of profemur 1.89-2.37. Color blackish with pale legs and halteres, as in the original description.

Head. AR 0.85-1.14 (5). Ultimate flagellomere 379-568 long (7). Temporal setae 8-10 (5) composed of 3 inner verticals, 5-7 outer verticals. Clypeus with 10-18 (5) setae. Tentorium 112-158 long, 30-40 (5) wide; stipes 108-162 long (6), 6-10 wide (6). Palp segment lengths (6): 28-46, 38-56, 88-126, 86-142, 134- 218. Apex of third palpomere with 2-5 sensilla, longest 16 µm long. Thorax. Acrostichals 8-13 (9), biserial; dorsocentrals 9-19 (8); prealars 2-6; supralars 0-1. Scutellum with 4-19 setae, irregularly biserial.

Wing (Fig. 1). VR 1.38-1.8. Brachiolum with 1-3 setae (7), R with 12-23, R1 with 11-15 (5), R4+5 with 19-32 (5) setae. Squama with 3-11 setae (6).

Figs. 1 - 4. Polypedilum (Tripodura) quinquesetosum (Edwards). Male imago. 1, wing; 2, tibial scale of fore leg; 3, hypopygium, dorsal view; 4, hypopygium with tergite IX removed, right, dorsal view, left, ventral view. Scale bar= 100 µm, except in Fig. 2.

Legs. Scale of fore tibia 30-42 (9) long (Fig. 2). Apex of fore tibia 44-62 (9) wide, of mid tibia 44-62 (9) wide, of hind tibia 50-70 (9) wide. Length and proportions of legs as in Table I.

Table I. Lengths (in μm) and proportions of legs of Polypedilum (Tripodura) quinquesetosm (Edwards) (male) (n = 6). Abbreviations: Femur (fe); Tibia (ti); Tarsomeres 1-5 (ta1-5); Leg Ratio (LR), ratio of metatarsus to tibia; beinverhältnisse» (BV), combined length of femur, tibia, and basitarsus divided by combined length of tarsomeres 2-5; «Schenkel-Scheine-verhältnis» (SV), ratio of femur plus tibia to metatarsus.

Hypopygium (Figs 3-4). Anal point 56-74 (6) long, 42-84 (6) wide at base, 20-28 (6) wide at apex. Tergite IX with 9-23 setae medially (6) and 14-18 setae at base of anal point (6). Phallapodeme 58-112 (9) long; transverse sternapodeme 34-62 (9) long. Gonocoxite 110-172 (9) long. Superior volsella club-shaped, with one inner seta, 3 apical setae and 3 lateral setae, 21- 56 (8) long, 10-20 (8) wide at base, 22-32 (8) wide at apex. Inferior volsella digitiform 74-118 long, 14-26 wide at base, 13-26 wide at apex, with 4-10 split setae subapically and one stout seta at apex. Gonostylus 144-172 (9) long. HV 2.21-2.89 (9). HR 0.68-1.05 (9).



Most of the Polypedilum species described from the Neotropics were established by Bidawid & Fittkau (1995) and Bidawid-Kafka (1996). These authors proposed a codification for several taxonomically informative characters that is adopted in this study; particularly, the anal tergal band (= Tergitebänder of Bidawid & Fittkau, 1995), base of anal point (= Typen des Ventrallobus of Bidawid & Fittkau, 1995) and type of superior volsella (= Typen von Anhang I of Bidawid & Fittkau, 1995).

The representatives of the subgenus Tripodura of the Neotropics could be divided into those that possess wing markings and those without this character state. In the latter group, P. (T.) quinquesetosum falls together with nine other species (Table II), of which three share two of the three characters analyzed. The species P. (T.) carijona Bidawid & Fittkau shares with P. (T.) quinquesetosum the anal tergal bands and inferior volsella type A, but a more detailed analysis of the volsella shows that the superior volsella of the former species is parallel-sided with rounded apex and with two inner setae. Besides these characters, differences exist also in the shape of the base of anal point, shape and number of setae of the inferior volsella, gonostylus, AR and LR. The species P. (T.) karyana Bidawid & Fittkau shares with P. (T.) quinquesetosum the shape of the base of anal point and inferior volsella type A, but a more detailed analysis of this last structure shows that the former species has one straight and short inner seta, three slightly curved apical setae and two long lateral setae. This species has a lower AR (0.22) than that of P. (T.) quinquesetosum. From the species described by Roback & Coffman (1983) only two characters were taken into account since the anal tergal bands were not included by these authors. The species P. titicacae Roback & Coffman and P. umayo Roback & Coffman share with P. (T.) quinquesetosus the type or superior volsella but both have a different shape of the base of anal point. Besides, the shape of the superior volsella is different from that of P. (T.) quinquesetosus since it possesses a projection directed medially, with one long lateral seta and several short apical setae. Polypedilum (T.) villcanota shares with P. (T.) quinquesetosus the character shape of base of anal point but the shape of the superior volsella type C of the former species differentiates both species.

Table II. Known species of Polypedilum (Tripodura) from the Neotropics with unmarked wings and bare membrane. Character codification follows Bidawid & Fittkau (1995).

Geographic distribution

The type localities of Polypedilum (T.) quinquesetosum have in common that they are located near lakes. The type locality of the holotype is near Lago Todos los Santos and the locality of the paratype is near Lago Llanquihue, both in the Valdivian district in Chile. The locality of the female paratype, although not included in this study, is Lago Correntoso in Argentina and is placed in the Deciduous district of the Subantarctic province (e.g. Cabrera & Willink, 1973).

Polypedilum (T.) quinquesetosum shows a transAndean distribution. This pattern is shared with several chironomid genera and species (Donato et al., 2009) [e. g. some Barbadocladius (Cranston & Krosch, 2011), Stictocladius (Sæther & Cranston, 2012)], suggesting that the Andes (at least at the lower elevation in this region) is not a barrier to dispersal.

The new records of P. (T.) quinquesetosum extend its distribution eastwards into Argentina. The Los Juncos lagoon is located in the Patagonian steppe and it is not permanent. One year after 2006 collecting, this lagoon was dry. The other locality is in the Somuncura Plateau, located in northeast Patagonia between 41°- 45° S and 66°- 68° W. This plateau has a total surface of approximately 30000 Km2, a maximum altitude of 1970 m a.s.l. and a volcanic origin (around 25 Ma.). The aquatic environments at the plateau are represented by streams, springs and lagoons. These bodies of water derive most of their water from precipitation in the form of rain, except Valcheta stream which has a thermal origin. The specimen of P. (T.) quinquesetosum was collected beside a small spring, and taking into account the rest of its records, the preference of this species to lentic environments is suggested.


We would like to thank the Darwin Initiative (DEFRA, UK) (project number 15/025) for providing funds to carry out this work. Our gratitude to Steve Brooks, Erica McAlister and Duncan Sivell of the NHM. We thank the comments and suggestions made by the two reviewers. We thank also to Fernanda Montes de Oca, Analía Garré and the park rangers of Nahuel Huapi National Park. This paper is the Scientific Contribution Nº 951 of the Institute of Limnology "Dr. R.A. Ringuelet" (ILPLA, CCT-La Plata, CONICET, UNLP).


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