Parachironomus lupus, Trivinho-Strixino, Susana, Silva, Fabio Laurindo Da & Roque, Fabio Oliveira, 2010

Trivinho-Strixino, Susana, Silva, Fabio Laurindo Da & Roque, Fabio Oliveira, 2010, A new species of Parachironomus Lenz, 1921 (Diptera: Chironomidae: Chironominae), and description of immature stages of two other species from the Neotropical Region, Zootaxa 2689, pp. 1-14 : 2-7

Parachironomus lupus sp. n.

( Figs. 1–16 )

Material examined. Holotype male, BRAZIL: São Paulo State, Itirapina, Represa do Lobo (22º11’07”S; 47º53’40”W), viii/1987, S. Trivinho-Strixino. Paratypes: 1 male, 2 larvae as holotype. 2 males with pupal and larval exuviae, 1 larva, as holotype except for Brotas, Lagoa Dourada (22o11’35”S; 47o55’03”W), 10/x/2003. 1 male, as previous except for xii/2002. 2 pupae, as previous except for 15/vii/2002, F. O. Roque.

Etymology. From Latin lupus (wolf) after the name of the reservoir where the larvae were collected (Represa do Lobo = Wolf Reservoir).

Diagnostic characters. Parachironomus lupus differs from other Parachironomus species by the combination of the following characters. Adult male: hypopygium with superior volsella ventrally bearing a large, pubescent expansion. Pupa: it is indistinguishable from P. alatus Beck & Beck, 1969 . Larva: premandible with 3 teeth, proximal tooth wider and anterior margin strongly scalloped of the ventromental plate.

Description. Male (n = 4 unless otherwise stated)

Dimensions. Total length [3.68] 3.20–3.78 mm. Wing length [1.78] 1.31–1.78 mm. Total length/wing length [2.06] 2.06–2.40. Wing length/length of fore femur [6.63] 5.66–6.63.

Coloration. Head yellowish brown, flagellum and maxillary palp pale brown. Thorax yellowish brown, scutellum pale brown. Wing clear, without spots; membrane transparent, veins pale brown. Legs pale brown. Abdomen and hypopygium brown.

Head. Antenna with 11 flagellomeres, AR [2.19] 2.00–2.19 (10), flagellum [1119] 975–1131 μm long. Eyes bare, with dorsomedian extension containing 5–6 facets. Eyes ratio [0.77] 0.55–1.07. Palpomere 1–5 lengths (in μm): [23] 20–25; [25] 25–31; [66] 66–80; [134] 126–135; [160] 160–271 (2). Frontal tubercles small, [22] 22 (1) μm long, [17] 17 (1) μm wide. Temporal setae [14] 12–14 (3), irregularly uniserial. Clypeus with [16] 12–16 setae.

Thorax. Antepronotum with 4 (1) lateral setae. Acrostichals [6] 6–10, biserial, beginning near antepronotum; dorsocentrals [7] 6–8, partly biserial; prealars [4] 3–5 (3); supraalar 1 (3); scutellars [6] 8 (3), biserial, irregular. Scutal tubercle absent.

Wing [0.52] 0.38–0.52 mm wide. Membrane without setae. Brachiolum with [2] 2 setae. Wing macrotrichia on C,R, R1, R4+5; submarginal row of setae on costa not reaching much further basal than R1; R with [17] 11–18 setae; R1 with [16] 11–16 setae; R4+5 with [22] 12–22 setae in distal half of vein. Squama with 1-2 setae. R2+3 ending about 1/3 distance between apices of R1 and R4+5.VR [1.20] 1.20–1.32 (3). FV [0.37] 1.20–0.51 (3).

Legs. Mid and hind tibiae each with two narrowly separated combs; each comb with a spur. Tarsal claws on all legs slender and hook-like, pulvilli well developed. Lengths and proportions of legs as in Table 1.

Hypopygium ( Figs. 1–4 ). Transversal anal tergite bands short, fading far apart medially. Caudal region of anal tergite without lateral projections. Anal point slender [55] 55–65 (3) μm long, slightly expanded distally, nearly 1.5 wider than the base, originating near caudal margin of anal tergite. Anal tergite with [16] 16–22 setae dorsomedially, around base of anal point, and laterally. Superior volsella, stout; enlarged distally with one setae arising from large pit; ventrally with a large, pubescent expansion. Inferior volsella pubescent, without caudal projection, not reaching beyond anal tergite. Gonocoxite with 4–5 medio-basal setae. Gonostylus long, about [5.50] 5.17–6.69 times as long as wide, narrowest in mid and distal regions and bearing numerous long to medium sized setae; 4–7 medio-distal setae. One apical seta. HR [0.65] 0.65–0.92.

Pupa (n = 4 unless otherwise stated)

Dimension. Abdomen 2.60–3.10 mm long.

Coloration. Exuviae pale brown.

Cephalothorax. Cephalic tubercles absent; frontal setae 58 (1) μm long (Fig. 5). Wing sheath 0.84–1.05 mm long. Thorax sparsely granulose dorsally (Fig. 6); scutal tubercle weakly developed; prealar tubercle present; antepronotals 2, precorneals 2, dorsocentrals 4. Basal ring weakly constricted medially (Fig. 7).

Abdomen. Shagreenation on T I–VIII covering most of tergite and with fine reticulations (Fig. 8). T II with posterior row of recurved hooks on distinct posteriorly projecting flap, uninterrupted medially, occupying about 1/3 the width of 2nd tergite. T III-VI with conspicuous posteromedian patch of spines higher on tergite V and VII; D5 stout, arising from large and prominent tubercles (Fig. 9). Sternites without conspicuous armature. Pedes spurii A present in segment IV, reduced to few spinules. Pedes spurii B inconspicuous. Segments I–IV with 0, 3, 3, 3 L setae, respectively; segments V–VII all with 4 taeniae; segment VIII with 5 taeniae. Anal lobe with complete fringe of about 67–86 taeniae; lamelliform dorsal seta present.

4th instar larva (n = 5 unless otherwise stated)

Coloration. Body light red and head yellowish. Procercus and anal setae pale brown. Posterior parapod claws pale yellowish.

Head 335–369 μm long, 250–300 (4) μm wide; ventral length 178–215 μm long. IC 0.70–0.86.

Antenna ( Fig. 10 ) 112–120 μm long, with 5 segments, basal segment 61–72 μm long, with ring organ 14– 16 (4) μm from base. AR 1.03–1.50. Antennal blade well developed arising from apical portion of basal segment reaching the middle of 4th segment; 4th segment nearly 3 times as long as 3rd segment.

Labrum. SI short, blade-like; SII blade-like, twice as long as SI; SIII seta-like; SIVa very small, 2 segmented. Pecten epipharyngis as in Figure 11 . Premandible with 3 teeth, proximal tooth wider; brush absent ( Fig. 12 ).

Maxilla. ( Fig. 13 ) Basal palp segment 21–26 (4) μm long, 15–17 μm wide, with ring organ 12–15 (4) μm from base.

Mandible ( Fig. 14 ) 139–150 μm long with a long apical tooth and 2 inner triangular teeth brownish. Seta subdentalis short, passing 1st inner tooth.

Mentum ( Fig. 15 ). With a middle tooth and 6 dark lateral teeth; middle tooth simple, not notched; 6th lateral tooth larger than 5th and set forward. Ventromental plate about 0.50-0.72 times as long as mentum width, with anterior margin strongly scalloped.

FIGURES 5–9. Parachironomus lupus sp. n., pupa. 5. Frontal apotome. 6. Thorax. 7. Basal ring. 8. Abdomen, dorsal view. 9. Posteromedian patches of spines and setae D5 on tergites III-VII. Scales: Fig. 5 = 100 μm; Fig. 7 = 50 μm; Figs. 6, 8 = 500 μm.

Abdomen ( Fig. 16 ). Procercus 0.82–1.18 times as long as wide, with 7 anal setae. Anal tubules 151–210 (2) μm long. Posterior parapod with pale yellowish claws.

Remarks. The best differential feature to separate the male of P. lupus from other Parachironomus species is the shape of the superior volsella, with its large pubescent ventral expansion. The pupal exuviae presents characteristics shared with P. alatus Beck & Beck , such as absence of cephalic tubercles; posterolateral corners of segment VIII without spines, tergites III to VII with D5 stout, arising from large and prominent tubercles. The larva of P. lupus is similar to that of P. alatus Beck & Beck , and can be separated by premandible with three teeth, proximal tooth wider and anterior margin strongly scalloped of the ventromental plate. These diagnostic characters found in P. lupus would be enough to support the proposition of a new genus or subgenus. However, in the absence of additional (e.g. molecular) evidence, we consider it as more adequate to hypothesize P. lupus as a species of Parachironomus .

Figures

FIGURES 1 – 4. Parachironomus lupus sp. n., male. 1. Hypopygium. 2. Hypopygium, ventral view (SEM). 3. Superior volsella, (a) dorsal view, (b) ventral view. 4. Ventral view of superior volsella (SEM). Scales: Fig. 1 = 100 μm; Fig. 3 = 50 μm.

FIGURES 10 – 16. Parachironomus lupus sp. n., larva. 10. Antenna. 11. Pecten epipharyngis. 12. Premandible. 13. Maxillary palp. 14. Mandible. 15. Mentum and ventromental plates. 16. Posterior end of abdomen. Scales: Figs. 10 – 14 = 50 μm; Fig. 15 = 250 μm.