Simulium duodenicornium Pepinelli, Hamada & Trivinho­Strixino, 2005

Pepinelli, Mateus, Hamada, Neusa & Trivinho-Strixino, Susana, 2005, Simulium (Thyrsopelma) duodenicornium, a new black fly species (Diptera: Simuliidae) from the Southeast Region of Brazil, Zootaxa 1040, pp. 17-29 : 19-28

Simulium duodenicornium Pepinelli, Hamada & Trivinho­Strixino New Species

( Figs.1–48 )

Female. General coloration black. Body length 2.8 mm (n = 1); thorax lateral length 1.3 mm (n = 1); wing length 2.5 mm (n = 1), wing width 1.1 mm (n = 1).

Frons, clypeus, and occiput dark brown with silver pruinosity; fronto­ocular triangle present ( Fig. 3 ); fronto­ocular suture absent. Antenna with silver pubescence, 0.55–0.60 mm in length; scape, pedicel, and proximal area of first flagellomere brownish yellow, remaining flagellomeres dark brown ( Fig. 4 ). Maxillary palpus brownish yellow; sensory vesicle elongated, occupying more than 1/3 of length of palpomere III; palpomere V twice length of palpomere III and IV. Mandible with 12 external serrations and 34–38 internal teeth. Lacinia with 25–26 retrorse teeth. Central region of cibarium with tubercles, cibarium arms sclerotized ( Fig. 6 ). Scutum black ( Figs. 1, 2 ), with gray­whitish hairs distributed in groups, with central line without hairs (light source anterior). Anepisternum dark brown; katepisternum light brown. Scutellum light brown with golden hairs; postnotum black. Wing vein Sc bare, R with setae, as in male wing ( Fig. 19 ). Foreleg with coxa, trochanter, and medial to proximal area of femur light brown; distal region and all tarsal segments dark brown ( Fig. 7 ). Middle leg with coxa, trochanter, femur, and most of tibia light brown; tibia, basitarsus, and penultimate tarsomere with distal region dark brown; other tarsomeres dark brown ( Fig. 8 ). Hind leg with coxa dark brown, trochanter light brown, femur, tibia and tarsomere light brown with apical region dark brown ( Fig. 9 ); calcipala as broad as long ( Fig. 5 ). Tarsal claw base slightly prominent ( Fig. 10 ). Femur with filiform and spatuliform setae and tibiae with filiform setae on all legs. Tergites dark brown. Basal fringe with thin, long, golden hairs. Cercus rounded; anal lobe with internal area concave medially, forming two short projection of similar width, with anterior projection more membranous ( Fig. 13 ); in ventral view as in Figure 11 . Hypogynial valves subovoid, covered with microtrichia ( Figs. 11, 14 ). Genital fork with stem long, lateral arms well developed and with large anterior processes; lateral arms forming subtriangular space ( Figs. 11, 12 ). Spermatheca subspherical, with internal cuticular microspines ( Fig. 15 ); spermathecal duct and area of attachment unpigmented.

Male. General body coloration black; body length 2.8 mm (n = 1); thorax lateral length 1.1 mm (n = 1). Wing length 2.4 mm (n = 1), wing width 1.2mm (n = 1).

Antenna with whitish pubescense, 0.5–0.6 mm in length; scape, pedicel, and first flagellomere light brown, remaining flagellomere dark brown, palpus dark brown, sensory vesicle small, occupying less than 1/5 of palpomere III; palpomere V about 2.2 times as long as palpomeres III and IV. Scutum black with golden hairs densely distributed ( Figs. 16, 17 ), without any silver or gray pattern. Scutellum dark brown, posnotum black. Anespiternum and katepisternum dark brown. Wing venation: Sc bare, Rs with hairs, and R and C with hairs and spines ( Fig. 19 ). Legs with same color pattern as in female, but tarsal claw differentiated, with prominent projection on base ( Fig. 18 ). Abdominal tergites black; basal fringe with long and thin, golden hairs. Gonocoxite and gonostylus brown; gonocoxite subrectangular; gonostylus elongated with 1 or 2 acute apical spines ( Fig. 21 ). Median sclerite rectangular with medial concavity ( Fig. 22 ). Paramere weakly sclerotized, poorly developed; membrane on central region with spicules ( Fig. 20 ). Ventral plate subrectangular, with anterior projection as in Figs. 23, 25, 27, 29 ; anterior projection enlarged distally and covered with setae.

Pupae ( Figs. 31–39 ). Body length 3.9–4.1 mm (mean = 4.0 mm, n = 5). Dorsal length of cocoon 4.0– 4.4 mm (mean = 4.1 mm, n = 5), ventral length 2.9–3.4 mm (mean = 3.2 mm, n = 5).

Cocoon boot shaped, thick and hard, without central projection ( Figs. 31, 32, 36 ). Gills with 12 short, thick, and rigid filaments, with tips pointed and highly sclerotized, without spicules in annular arrangement ( Figs. 33, 34 ). Frontoclypeus with 2 pairs of short, stout, and simple frontal trichomes, 1 pair of spines above frontoclypeus ( Fig. 35 ), surrounded by small rounded tubercles. Thorax, dorsally, with 5 pairs of spiniform trichomes ( Fig.

37). Abdomen as in Figs. 38 and 39 . Tergite I with 1 pair of sublateral setae ( Fig.38 a). Tergite II with 4 pairs of stout setae, 2 pairs of thin sublateral setae, and many small tubercles especially in anterior to medial region of tergite ( Fig. 38 b). Tergites III and IV each with 4 anteriorly directed pairs of hooks on posterior margin ( Figs. 38 c, d). Tergites V–IX with comblike groups of fine posteriorly directed spines on anterior margin ( Fig. 38 e). Sternites III–IX with anterior medial comblike groups of microspines ( Fig. 39 a). Sternites V–VII with 2 pairs of stout, bifid hooks on posterior margin ( Figs. 39 b, c, d).

Larvae (last instar) ( Figs. 40–48 ). Length: 6.2–7.5 mm (mean = 6.9 mm, n = 5); head capsule lateral length: 0.5–0.6 mm (mean = 0.53, n = 5), dorsal width: 0.79–0.88 mm (mean = 0.82, n = 5).

General coloration grayish black (in Carnoy’s solution). Head capsule with negative pattern as in Fig. 44 . Cervical sclerites small, eliptical, free in membrane, each with thin, elongated sclerite anteriorly ( Figs. 40, 44 ). Postgenal cleft subtriangular, widest medially ( Figs. 41, 42 ), with thin, dark membrane covering its entire surface ( Fig. 41 ). Postgenal bridge 0.5 times as long as hypostoma ( Fig. 42 ). Subesophageal ganglion not pigmented. Antenna as long as labral fan stalk; distal and proximal articles smaller than medial article (proportions of articles proximal to distal, excluding apical sensillum, 1: 2.5–2.6: 0.9) ( Fig. 45 ). Hypostoma with pigmented anterior margin and 9 apical teeth: lateral teeth larger and more blunt than remaining teeth, 3 small median teeth, and 4 larger, blunt intermediate teeth, lateral serrations absent and 7 or 8 setae per side ( Fig. 43 ). Labral fan with 53–59 primary rays. Body covered with ovoid setae ( Fig. 46 ). Ventral tubercles absent. Anterodorsal arms of anal sclerite shorter in length than posteroventral arms ( Fig. 47 ). Posterior proleg bearing approximately 178–184 rows (n = 3), with 26–31 hooks. Anal papillae with 3 branches, each with 25–27 finger­shaped lobes ( Fig. 48 ).

Types

Holotype ( MZUSP) male (pinned), Cachoeira stream (Cahoeira dos Pretos), 22o57S; 46o10W, Mantiqueira mountain chain, Joanópolis County, State of São Paulo, Brazil; collectors M. Pepinelli and N. Hamada, 22/v/2004.

Paratype ( MZUSP) 1 pinned female, 1 pharate male, and 1 pharate female with genitalia mounted on permanent slide; 5 larvae and 5 pupae in 80% ethanol, same locality as holotype, collectors M. Pepinelli, R.F. Gutierrez, F.O. Roque, 22/viii/2004; INPA 1 pharate male, head and thorax pinned and remainder on slide with its respective pupal exuviae, 1 pharate female, thorax pinned and remainder on slide with its pupal exuviae; 5 larvae and 5 pupae, in 80% ethanol, same locality as holotype, collectors M. Pepinelli, R.F. Gutierrez, F.O. Roque, 22/viii/2004; INPA 10 larvae and 10 pupae in 80% ethanol, same locality as holotype, collectors N. Hamada, N.H. Fearnside, B.Ronchi­Teles, 10/i/2005; INPA 10 larvae and 10 pupae in 80% ethanol, same locality as holotype, collector N. Hamada 1/iii/2005; NHM 5 larvae and 5 pupae, same locality as holotype, collector N. Hamada 1/iii/2005.

Additional Material Examined

Simulium guianense s.l.

French Guiana.

INPA ­ 1 male and its pupal exuviae on slide, Maroni River, 17/vi/1999. Collectors: N. Hamada, F. Fouque; 1 pharate male and 1 pharate female on slide, Maroni River, 17/vi/ 1999. Collectors: N. Hamada, F. Fouque.

Etymology

The name of this species is derived from duodeni (L.) = twelve each, and cornus (L.) = horn, in reference to the number and shape of the pupal gill filaments.

Taxonomic Discussion

The female of S. duodenicornium n. sp. has a black scutum with silver setae arranged in groups ( Figs. 1, 2 ). This pattern is similar to that of other species in the subgenus Thyrsopelma , with the exception of S. scutistriatum Lutz , in which the thorax is brownish red. However, the female of the new species can be distinguished from the females of the other species of Thyrsopelma by the anal lobe ( Fig. 13 ); this structure is similar to those of S. guianense s.l. Wise and S. orbitale Lutz in that it has a membranous anterior region, but in the new species the internal side of the anal lobe is concave in the medial region, forming two short projections of similar width.

The male of S. duodenicornium can be distinguished from males of the other species in this subgenus by the shape of the genitalia and the coloration of the scutum. The new species has a black scutum, covered with golden setae, without bands ( Figs. 16, 17 ). The other species in this subgenus have a silver thoracic pattern, with the exception of S. perplexum Shelley, Maia­Herzog, Luna Dias & Couch , which has a scutal pattern similar to that of the female of the new species. Simulium scutistriatum has a dark brown scutum ( Shelley et al. 1989, Coscarón, 1991).

The pupa of the new species has 12 thick gill filaments, with the apices pointed and heavily sclerotized and without spicules in annular arrangements ( Figs. 33, 34 ). Four other species in the subgenus Thyrsopelma have pupae with 12 gill filaments, but they can be distinguished from the new species by the following combinations of characters: S. guianense s.l., S. perplexum , and S. hirtipupa Lutz have gill filaments with spicules or projections in an annular arrangement and filaments thinner than those of the new species ( Maia­Herzog et al. 1985; Shelley et al. 1989, 1997). Additionally, S. hirtipupa has protuberances on the cocoon and a large number of trichomes on the frontoclypeus, which were not observed in the new species. Although S. scutistriatum has 12 gill filaments, the cocoon shape is different, with the anteroventral margin more elongated and the frontoclypeus bearing several acuminate tubercles. The pupa of S. duodenicornium has small tubercles distributed evenly on tergite II, a condition not recorded in other species in the subgenus. Shelley et al. (1997) reported one row of simple hooks on tergite V of S. guianense s. l. pupae; however, in the specimens of S. guianense s. l. that we examined from French Guiana, we did not observe a row of hooks on this tergite.

The larva of Simulium duodenicornium n. sp. has an anal lobe of up to 27 lobes, whereas the other species in this subgenus with known larvae have anal lobes of 5–15 lobes. However, in S. scutistriatum the larvae have 30 lobes. Simulium scutistriatum larvae have an anal disc with 280–300 rows ( Coscarón 1991), whereas the new species has approximately 180 rows. Larvae of this new species have the body cuticle covered with ovoid setae that appear to be wider than those in the other species of the subgenus. However, this observation needs to be confirmed.

Bionomics

Larvae and pupae were collected in only one stream, which had a streambed of sand, small stones, and boulders. They were collected on stems, leaves, and roots of trailing vegetation, in areas where the flow was fast and highly turbulent. The stream had clear water in the first two collection periods (May and August 2004), but the water carried sediment in the last two collections (January and March 2005) due to constant rainfall. In the area where larvae and pupae were collected, the stream bank was covered with low riparian vegetation and some grass; upstream of the waterfall there were some areas of cattle pasture. In May 2004, water temperature was 15.6°C, pH 7.3, and electrical conductivity 14 µs/cm. The altitude at the collection area was 902 m. The females of this species were not collected biting humans during the field work.

Figures

FIGURE 38. Simulium duodenicornium n. sp. pupa. 38. Abdominal segments dorsal view, a: lateral setae of tergite I; b: setae and small tubercles on tergite II, c: hooks on tergite III; d: hooks on tergite IV; e: group of microspines on tergites V – IX.

FIGURE 39. Simulium duodenicornium n. sp. pupa. 39. Abdomen, ventral view, a: group of microspines on sternites III – V; b: hooks on sternite VI; c: hooks on sternite VII; d: hooks on sternite VIII.

FIGURES 1 – 10. Simulium duodenicornium n. sp. female. 1. Scutum, dorsal view. 2. Scutum, dorsolateral view. 3. Fronto­ocular triangle. 4. Antenna. 5. Calcipala and pedisulcus. 6. Cibarium. 7. Foreleg. 8. Middle leg. 9. Hindleg. 10. Claw of foreleg.

FIGURES 11 – 15. Simulium duodenicornium n. sp. female. 11. Terminalia, in situ. 12. Genital fork. 13. Cercus and anal lobe. 14. Hypogynial valves, ventral view. 15. Spicules on spermatheca wall.

FIGURES 16 – 22. Simulium duodenicornium n. sp. male. 16. Scutum, dorsal view. 17. Scutum, dorsolateral view. 18. Claws of foreleg. 19. Wing base. 20. Paramere. 21. Gonocoxite and gonostylus, with one or two apical spines. 22. Median sclerite.

FIGURES 23 – 30. Male terminalia in situ, ventral view. 23. S. duodenicornium. 24. S. guianense. 25 – 30. Ventral plate of S. duodenicornium and S. guianense. 25, 27, 29. S. duodenicornium. 25. Ve n tr a l vi e w. 27. Dorsal view. 29. Lateral View. 26, 28, 30. S. guianense. 26. Ventral plate, ventral view. 28. Ventral plate, dorsal view. 30. Lateral view.

FIGURES 31 – 37. Simulium duodenicornium n. sp. pupa. 31. Habitus, dorsal view. 32. Habitus, lateral view. 33, 34. Gill filaments. 35. Pair of spines above frontoclypeus. 36. Anterior region of cocoon. 37. Spiniform trichomes on thorax.

FIGURES 40 – 48. Simulium duodenicornium n. sp. larva. 40 – 44. Head capsule. 40. Dorsal view, in situ. 41. Ventral view, in situ. 42. Ventral view of postgenal cleft. 43. Hypostoma. 44. Dorsal view showing cervical sclerites. 45. Antenna. 46. Ovoid setae on body cuticle. 47. Anal disc. 48. Anal lobes.