Parochlus carolinae, Rodríguez, Mariana S., Paggi, Analía C. & Medina, Ana, 2009

Rodríguez, Mariana S., Paggi, Analía C. & Medina, Ana, 2009, A new Neotropical species of the genus Parochlus Enderlein, 1912 (Chironomidae: Podonominae) and new distribution in Argentina, Zootaxa 2300, pp. 39-46 : 40-45

Parochlus carolinae sp. n.

Type material. Holotype male: ARGENTINA, San Luis Province, Carolina stream, 66º2'S, 32º50'W, 17.XI.2006, entomological net, M. Donato col. ( MLP). Paratypes: 1 larval exuviae and pupa, 13.VII.2006, drift net, ( MLP); 1 pupal exuviae, same data as holotype; 1 pupal exuviae and 2 pupae, Rio Grande river, upstream, 7.IX.2006, drift net, Medina & Paggi col. ( ILPLA).

Etymology. The name of the new species refers to its type locality.

Diagnostic characters. As in Parochlus duseni ( Brundin 1966) the male adult of P. carolinae sp. n. differs from other Parochlus species by having hairy eyes over the whole surface and could be distinguished from P. d u s e n i by the following characters: a fully developed antennae with 14 flagellomeres (reduced antennae with 12 flagellomeres in P. duseni ), wing cell r1 extremely narrow (wing cell r1 broad in P. duseni ) and costa long, reaching wing tip (costa short, not reaching wing tip in P. duseni ). The male is separable from P. araucanus by having a lower length ratio value between 13–14 flagellomeres and a lower number of supraalar, scutellar and prealar setae. It differs from P. kiefferi by having a smaller overall size, distinctly shorter wing, non dusky halteres, no anepisternal or preepisternal setae, shorter and narrower antennal segments, the last flagellomere without apical bristle, shorter palpomeres, lower VR, shorter tibial spurs, lower BV and SV of fore, mid and hind legs, lower HR and HV, wing with M1+2 and Cu1 straight, narrower basal portion of apical lobe and broader distal portion of gonostylus, shorter gonostylus, with shorter p, t and y setae, lower number of prealar, scutellar and scale setae ( Saether 1967).

The pupae of the new species have a well developed distinct thoracic horn, broader at the apex than at the base. The porous plate has a coup-shaped form, somewhat longer than broad and its surface is provided with very small well-marked 5–6 porous groups, like in P. araucanus . It also has an additional reticulate structure beneath the porous plate upper surface, as in P. rieki Brundin, 1966 . Some specimens present a lobe and sharp incisures apical margin of the porous plate ( Figure 12 ), which resembles the trigonocerus group as well as P. kiefferi ( Brundin 1966) . The stalk is always considerably shorter than the plate, tapering proximally, and dorsally showing weakly developed transverse furrows and spines. The felt chamber does not end at the border between the stalk and the porous plate, but it extends into the porous plate. The setae of the anal spurs are also specific. The median seta is shorter than the lateral seta and the spur; the lateral seta is placed in the distal third of the anal spurs.

The pupae from P. carolinae can be distinguished from P. araucanus by having a stouter thoracic horn, with a shorter and more serrated stalk, a triangular porous plate, much shorter anal spur median setae and longer lateral setae that is never terminally inserted. The pupa differs from P. kiefferi by having its anal spur with two well developed setae, the lateral setae never being in terminal position and a shorter stalk of the thoracic horn.

Description. Male (n = 1) ( Figures 1–8 )

Body length 2 mm; wing length 1.51 mm, width 0.41 mm. Body length/wing length ratio 1.32. Wing length/wing width ratio 3.66.

Coloration. Coloration uniformily dark brown; head dark brown; thorax slightly shining, mesonotum, preepisternum and postnotum dark brown, scutellum yellowish; abdomen and legs uniformily light brown, wings grayish, halteres yellowish pallid.

Head ( Figure 1 ). Height 0.48 mm. Eyes reniform, with a dorsomedial extension, hairy. Antenna with 14 flagellomeres, each one with dense setae. Length of antennal segments: 72, 48, 36, 28, 29, 40, 40, 40, 40, 42, 40, 39, 40, 144, 87. Diameters of scapus and segments 2–5: 142, 30, 25, 25, 26. Last segment with bristles 45– 60 µm long whorl and 20 µm long strongly curved distally hyaline sensory bristles at apex ( Figure 7 ). AR 0.5; setae of head: temporals 16, frontals 8, postorbitals 8, clypeals 7; frontal tubercles absent; clypeus width 120 µm; tentorium 140 µm long; palpomere lengths: 34, 61, 91, 81, 106; first palpomere hyaline, remaining palpomeres pigmented. Proboscis extended; mandibles serrated, 65 µm long.

Thorax ( Figure 2 ). Antepronotum notched at middle. Chaetotaxy: Aps 4, Dc 44, Pa 24, Su 2, Scts 8, Ac 18, Pscts 4. Anapleural suture 165.6 µm long; pleura without setae.

Wings ( Figure 8 ). Wing length 1.51 mm; membrane and veins with c. 4 µm long microtrichia and c. 37 µm long macrotrichia. R1 ending in distal third of the wing and more than half as long as R4+5. Costal extension 0.12 mm long, reaching tip of to wing tip, R2+3 absent with thickening on R1 and R4+5, R4+5 close to R1 and curving gently to terminate close to wing apex, rm and mcu equal in length. Squama with 4 setae, alula bare, brachiolum with 2 setae. C, R, R1, R4+5, M and Cu setose. Anal lobe not right-angle. RL 628 µm, Cu 538 µm long; VR 0.86. Halteres covered totally with microtrichia, only visible at 400X resolution.

Legs. Lengths and proportions as in Table. Bristles mostly uniformly dispersed reaching 0.5–1.5 the width of segment on front femora, 0.5–2 on middle and hind femora, 1–2 on front and middle tibiae, 1–2.5 on hind tibia. Spur of front tibia 36 µm long ( Figure 4 ); spurs of middle tibia 30 µm and 22 µm long ( Figure 5 ); of hind tibia 30 µm and 20 µm long. All tibial spurs with lateral spinules, bearing an annular mark situated at c. 1/4 length from its base. Comb of hind tibia with 10 setae 26–44 µm long ( Figure 6 ). Empodium present, reaching 40 µm on front legs. Pulvilli lacking. Claws c. 27.2 µm long, with 3 long ventral hairs at base, 4–5 shorter dorsal hairs and 4–5 blunt apical teeth.

TABLE. Length (in µm) and leg proportions of Parochlus carolinae sp. n.

fe ti ta1 ta2 ta3 ta4 ta5 LR BV SV p1 530 538 318 171 90 57 65 0.59 3.62 3.36 p2 595 538 245 163 82 57 65 0.45 3.75 4.62 p3 653 702 351 204 122 57 65 0.5 3.8 3.86 Abdomen. Tergites and sternites covered with dense setae concentrated primarily at lateral side on tergites and in the middle on sternites.

Hypopygium ( Figure 3 ). Tergite IX 146 µm long with 42 setae. Coxite with many bristles dorsally on inner side. Apodemes strongly sclerotised, phallapodeme 77 µm long; transverse sternapodeme 51 µm long. Gonocoxite 150 µm long; gonostylus 81 µm long, swollen and setose at base, with c. 7 setae 61 µm long. extended into a pair of lobes; basis of gonostylus 38 µm long; apical lobe 60 µm long, subapical lobe 38 µm long; podonomine seta (p) 60 µm, terminal seta of the apical lobe (t) 10 µm, terminal seta of the subapical lobe (t) 4 µm, ventral seta of the apical lobe (x) 17.5 µm, dorsal seta of the subapical lobe (y) 12.5 µm. Anal point and virga absent. HR 1.85; HV 3.

Pupa (n = 5, 3 pupae and 2 pupal exuviae except when otherwise stated) ( Figures 9–12 )

Total length 2.7–3.4, 3 mm (3). Pale brown with darker apophyses.

Cephalothorax. Frontal apotome with pair of short lateral setae ( Figure 9 ). Thoracic horn well developed, 248–331, 293 µm long (5); porous plate 162–203, 193 µm wide (5); porous plate 207–257, 230 µm long (5); stalk 61–87, 71 µm long (5) ( Figure 11 ). Posterior pronotal setae present. Frontal setae 10 µm long (1). Anterior dorsocentral (Dc1) 10 µm (2); Dc 2 10–16, 13 µm (2); Dc3 7 µm (1) and Dc 4 20–30, 25 µm (2) long and distance from Dc1–Dc3 to Dc4 193 µm. Precorneals up to 16 µm long.

Abdomen. Light brown, margins darker, shagreen uniformly coloured. Number of setae on tergite VIII 5 (4). Conjunctives broad without setae. Ventral lamella on second segment. Anal spurs of anal lobe 41–61, 54 µm long (4). Two anal macrosetae 315–331, 323 µm long (4). The median seta of the anal spurs 8–12, 8 µm long (2); lateral seta 28–32, 30 µm long (3) ( Figure 10 ).

Larva (n = 1) ( Figures 13–14 )

Head. Dark brown to black head with much darker mentum and mandible. Eye spot single and compact. Head capsule 373 µm long; 265 µm wide. Postmentum 206 µm long.

Antenna with third segment annulated ( Figure 13 ); length of articles: 60, 20, 8, 2, 4 µm; AR 1.76; blade broad 24 µm long, accessory blade narrower 4 µm long. Mandible length 81 µm. Mentum width 69 µm, median tooth width 14 µm ( Figure 14 ).

Geographical distribution and ecology. The studied region is a part of the San Luis hills which belong to the Pampasic Hills System, located in the north-central area of San Luis Province, Argentina, corresponding to the Chaco wetland ( Canevari et al. 1998). The Carolina stream is a tributary of the Grande River and is situated in the centre-north part of the province, at altitude of 1620 m a.s.l. It rises in La Carolina village and presents a dense drainage network made up of a series of tributaries of different size, some of which are temporary and flow only during the rainy season ( Tripole et al. 2000). The Grande River belongs to the upper valley of the Rio Quinto River and drains over the oriental slope of the San Luis hills. It rises at 2160 m a.s.l., run over around 24 km and its average annual flow is 2.81 m ³s -1 ( Medina & Paggi 2004).

Both lotic systems present their own hydrological characteristics of headwaters, in which a thick pebble and gravel substratum prevails, having an 0.14 m average depth, an 0.18 ms -1 average speed, a 14.8 °C average temperature, a 266.25 µScm -1 average conductivity, a 10.4 mgl -1 dissolved oxygen average and 3 (FTU) average turbidity ( Medina et al. 2008). The climate is semiarid, with estival rainfalls and an annual average precipitation of 500–600 mm (Ceci & Cruz Coronado 1981).

Brundin claimed in 1966 that Parochlus was a successful genus, showing great adaptation to different types of habitats: from running waters to still and shallow ones at low temperatures (0.5–8.8 °C) both in the Northern and Southern Hemispheres. The new species was recorded at higher water temperature (14.8 °C average) as those stated by Brundin showing a new kind of adaptation for this genus. Other members of the subfamily such as Podonomus species are also present in these environments and have recently been recorded in Brazil under similar ecological factors ( Roque & Trivinho-Strixino 2004). Furthermore, the highest sites (Monte and higher Yungas) from Northwestern Argentinean stream systems has firstly recorded Podonominae taxa also at high temperature ratios ( Tejerina & Molineri 2007).

If we seek to find out why this kind of adaptation has occurred we must consider the fact that this new record appeared in a transitional geographical zone, between a moderately high altitude and relatively low latitude, as is the San Luis Hills System. A good characterization of this zone is discussed in Medina et al. 2008.

Several studies have shown the dominance of warm eurythermal taxa in tropical-subtropical zones and the dominance of a cold stenothermal fauna in templated Andean Patagonian zones, including the Podonominae ( Cranston 1995, Lobinske et al. 1996, Higuti et al. 1993, Corigliano et al. 1996). The presence of Parochlus carolinae sp. n. in San Luis Province constitutes an Andean-Patagonian element in a zone of transition and biogeographic mix between the big dry lands of the south and the west (Patagonia, Monte, Puna) with the wetlands of north and the east of South America (Chaco). The “Monte” Biogeographic Province was defined as an ecotone between the “Brazilian and Patagonian regions” ( Morrone 2004). This biogeographic system is very important for migration and colonization of species in this part of the continent ( Bucher 1982, Cabrera & Willink 1973).

Figures

FIGURES 9 – 14. Parochlus carolinae sp. n. Pupa (9) frontal apotome, dorsal view; (10) anal segment; (11) and (12) thoracic horns. Larva (13) antenna; (14) mentum. Scale bars: 100 µm.

FIGURES 1 – 8. Parochlus carolinae sp. n. Male imago (1) head, frontal view; (2) thorax, lateral view; (3) hypopygium, dorsal view; (4) spur of front tibia; (5) spur of middle tibia; (6) spur and comb of hind tibia; (7) antenna; (8) wing. Scale bars: (1 – 5, 7 – 8) 100 µm; (6) 50 µm.