Simulium (Simulium) tani Takaoka & Davies, 1995

Takaoka, Hiroyuki, Sofian-Azirun, Mohd, Ya’Cob, Zubaidah, Chen, Chee Dhang, Lau, Koon Weng, Low, Van Lun, Pham, Xuan Da & Adler, Peter H., 2017, The black flies (Diptera: Simuliidae) of Vietnam, Zootaxa 4261 (1), pp. 1-165 : 147-153

Simulium (Simulium) tani Takaoka & Davies, 1995 (complex)

Simulium (Simulium) tani (complex): Morphoform ‘a’: Takaoka et al., 2015a: 85 –86.

Specimens examined. Seven females and 15 males (all reared from pupae), collected from a river (width 8–10 m, depth 10–15 cm, bottom of pebbles, water temperature 17˚C, exposed to the sun, elevation 162 m, 18˚58’45.918”N/109˚50’10.693”E), fast flowing in a natural forest, Pu Mat , Nghe An Province, northern Vietnam, 9-XII-2015, H. Takaoka, M. Sofian-Azirun, C.D. Chen, & K.W. Lau; four females and four males (all reared from pupae), collected from a stream (width 1.0– 1.5 m, depth 10–15 cm, bottom of pebbles, water temperature 17˚C, partially shaded, elevation 162 m, 18˚58’45.918”N/109˚50’10.693”E), moderate to fast flowing near a natural forest, Pu Mat, Nghe An Province, northern Vietnam, 9-XII-2015, H. Takaoka, M. Sofian-Azirun, C.D. Chen, & W. K. Lau ; 13 females and 14 males (all reared from pupae), collected from a stream (width 1.5–3.0 m, depth 10– 15 cm, bottom of sands and pebbles, water temperature 18˚C, exposed to the sun, elevation 73 m, 19˚30’45.487”N/ 105˚09’29.261”E), moderately flowing near a natural forest, Chau Dinh , Quy Chau, Nghe An Province, northern Vietnam, 9-XII-2015, H. Takaoka, M. Sofian-Azirun, C.D. Chen & K. W. Lau.

Distribution. Vietnam (Lam Dong and Nghe An).

Remarks. This species is a species complex comprising 11 cytoforms, of which nine are reported from Thailand ( Adler and Crosskey 2016). In Vietnam, two morphoforms (‘a’ and ‘b’) were recognized, both of which are morphologically distinguished from S. (S.) tani (= cytoform K) originally described from Peninsular Malaysia ( Takaoka et al. 2015a). Morphoform ‘a’ is chromosomally divided into two cytoforms (Adler et al. 2016) and is also shown to include an additional possible cryptic taxon by a DNA sequence-based analysis (Low et al. 2016).

Simulium (Simulium) suoivangense Takaoka & Pham sp. nov.

Simulium (Simulium) tani (complex): Morphoform ‘b’: Takaoka et al., 2015a: 85 –86.

Morphoform ‘b’ of S. (S.) tani (complex) reported from southern Vietnam ( Takaoka et al. 2015a) is here described as a distinct species and a new name S. suoivangense is given.

Female. Body length 2.4–2.6 mm. Head. Slightly narrower than thorax. Frons black, shiny with bright reflection when illuminated at certain angles, with several dark stout hairs along lateral margins; frontal ratio 1.3– 1.4:1.0:1.2–1.3; frons:head ratio 1.0:3.5–4.0. Fronto-ocular area well developed, short, directed laterally, and rounded apically. Clypeus black, slightly shiny, moderately covered with dark-brown medium-long hairs though mediolongitudinal portion widely bare. Labrum 0.5–0.6 times length of clypeus. Antenna composed of scape, pedicel and nine flagellomeres; antenna dark brown, except scape, pedicel and base of first flagellomere yellow. Maxillary palp with five segments, medium brown except segment 3 dark brown; proportional lengths of third, fourth, and fifth segments 1.0:1.2–1.3:2.6–2.8; third segment ( Fig. 66 A) of moderate size, with long ellipsoidal sensory vesicle (0.5–0.6 times length of third segment) having medium-sized opening. Maxillary lacinia with 14– 16 inner and 19 or 20 outer teeth. Mandible with 31 or 32 inner and 11 outer teeth. Cibarium ( Fig. 66 B) with 82–90 minute processes near posterodorsal margin. Thorax. Scutum black, shiny with bright reflection when illuminated at certain angles, moderately covered with dark short fine hairs interspersed with several dark-brown long upright hairs on prescutellar area. Scutellum dark brown, shiny when illuminated at certain angles, covered with darkbrown upright long hairs. Postnotum brownish black, shiny when illuminated at certain angles, and bare. Pleural membrane bare. Katepisternum longer than deep, brownish black, shiny when illuminated at certain angles, and bare. Legs. Foreleg: coxa whitish yellow; trochanter light brown with base whitish yellow; femur light to medium brown with apical cap dark brown; tibia medium brown except apical cap dark brown, with median outer surface widely white and with bright white sheen when illuminated at certain angles; tarsus black, with moderate dorsal hair crest; basitarsus greatly dilated, 4.3–4.6 times as long as its greatest width. Midleg: coxa dark brown with posterolateral surface brownish black; trochanter medium brown with base whitish yellow; femur medium to dark brown except apical cap brownish black; tibia medium brown except base yellowish white and apical cap brownish black, and with whitish sheen widely on posterior surface when illuminated at certain angles; tarsus medium brown except basal three-fourths or two-thirds of basitarsus and base of second tarsomere yellowish white. Hind leg: coxa medium to dark brown; trochanter whitish yellow; femur dark brown except base whitish yellow; tibia medium to dark brown except base yellowish white and with whitish sheen widely on posterior surface when illuminated at certain angles; tarsus medium brown except little more than basal two-thirds of basitarsus and basal half of second tarsomere yellowish white; basitarsus ( Fig. 66 C) nearly parallel-sided, 5.4–5.6 times as long as wide, and 0.8 and 0.7 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 66 C) moderately developed, nearly as long as wide, and 0.4 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 66 C) well developed; claw simple, without tooth. Wing. Length 1.7–2.0 mm. Costa with dark spinules and hairs; subcosta haired except apical half to one-fifth bare; basal section of radius bare; R1 with dark brown spinules and hairs; R2 with dark-brown hairs; hair tuft on base of radius dark brown; basal cell absent. Halter . White except basal portion darkened. Abdomen. Basal scale dark brown, with fringe of yellow hairs. Dorsal surface of abdomen medium brown to brownish black, with dark short hairs; tergite 2 shiny and silvery iridescent when illuminated at certain angles and tergites 6–9 shiny and iridescent when illuminated at certain angles. Ventral surface of segment 7 with pair of weakly sclerotized submedian sternal plates. Terminalia . Sternite 8 ( Fig. 66 D) well sclerotized and bare medially, covered with 9–13 long and medium-long stout hairs and three to six short fine hairs on each side. Ovipositor valve ( Fig. 66 D) nearly triangular, rounded posteromedially, membranous except inner margin weakly sclerotized, densely covered with microsetae together with seven to nine short fine hairs; inner margin nearly straight or sinuous or slightly concave medially. Genital fork ( Fig. 66 E) of inverted-Y form; stem slender and well sclerotized; arms of moderate width, each with distinct projection directed forward from lateral ridge. Paraproct in ventral view ( Fig. 66 F) pointed posteromedially, moderately concave anterolaterally, and with strongly sclerotized anteromedial surface bearing five sensilla; paraproct in lateral view ( Fig. 66 G) somewhat produced ventrally and slightly posteriorly, 0.6 times as long as wide, covered with 18–22 medium-long stout hairs and numerous microsetae on lateral and ventral surfaces. Cercus in lateral view ( Fig. 66 G) short, rounded posteriorly, 0.6 times as long as its greatest width, and covered with medium-long and short stout hairs. Spermatheca ( Fig. 66 H) ovoidal, 1.2–1.3 times as long as wide, well sclerotized except duct and narrow area of juncture with duct unsclerotized, without discernible reticulate surface patterns; minute internal setae present; accessory ducts subequal in thickness to each other and slightly thicker than main duct.

Male. Body length 2.5–2.7 mm. Head. Slightly wider than thorax. Upper eye medium brown, consisting of large facets in 17 or 18 vertical columns and in 18 horizontal rows. Clypeus black, thickly white pruinose, silvery shiny when illuminated at certain angles, covered with dark-brown hairs along and near lateral margins (most of central portion bare). Antenna composed of scape, pedicel and nine flagellomeres, brownish black except scape, pedicel and base of first flagellomere dark yellow to light brown; first flagellomere elongate, 1.5 times as long as second one. Maxillary palp grayish to dark brown, composed of five segments with proportional lengths of third, fourth, and fifth segments 1.0:13:2.7–2.8; third segment ( Fig. 67 A) widened apically; sensory vesicle ( Fig. 67 A) small (0.2 times as long as third segment), ellipsoidal, and with small opening. Thorax. Scutum black, with white pruinose pattern, i.e., anterior pair of triangular spots (not sharply pointed posteriorly) on shoulders extended posteriorly along lateral margins but not connected to large transverse spot entirely covering prescutellar area; these pruinose areas silvery or bluish iridescent when illuminated at certain angles; scutum uniformly and densely covered with brassy recumbent short hairs interspersed with dark-brown long upright hairs on prescutellar area. Scutellum brownish black, with several dark-brown long upright hairs. Postnotum brownish black, white pruinose when illuminated at certain angles and bare. Pleural membrane bare. Katepisternum longer than deep, brownish black, thinly white pruinose and shiny when illuminated at certain angles, and bare. Legs. Color as in female except hind tibia with basal small portion yellow, and hind basitarsus yellowish white on basal half or little less. Fore basitarsus greatly dilated, 5.4–6.1 times as long as its greatest width. Hind basitarsus ( Fig. 67 B) much enlarged, gradually widened from base to apical two-fifths, then slightly narrowed toward apex, 3.6–3.8 times as long as its greatest width, and 0.8–0.9 and 0.9 times as wide as greatest widths of hind tibia and femur, respectively; calcipala ( Fig. 67 B) small, nearly as long as wide, 0.2 times as wide as greatest width of basitarsus; pedisulcus ( Fig. 67 B) well developed. Halter . White except basal portion darkened. Wing. Length 1.6–1.7 mm. Other characters as in female except subcosta bare. Abdomen. Basal scale brownish black, with fringe of pale (though basally dark) long hairs. Dorsal surface of abdomen brownish black to black, with dark short hairs; segments 2 and 5–7 each with pair of silvery or bluish iridescent spots dorsolaterally, those on segment 2 broadly connected in middle to each other. Genitalia. Coxite in ventral view ( Fig. 67 C) nearly quadrate, covered with stout hairs near posterior margin. Style in ventral view ( Fig. 67 C) elongate, gradually tapered from base to middle, then nearly parallel-sided, with apical spine; style in ventrolateral view ( Fig. 67 D) elongate, 2.6 times as long as its greatest width at basal one-third, slightly widened from base to basal one-third, much tapered toward apical one-third, then slightly widened toward tip; style in medial view ( Fig. 67 E) 1.6 times as long as coxite, much produced dorsally near base and with 8–12 small cone-like spines on dorsal surface. Ventral plate in ventral view ( Fig. 67 C) well sclerotized, with body subquadrate (though rounded on each posterolateral corner), 0.7 times as long as wide, posterior margin somewhat convex, and with round projection directed ventrally which is covered with many minute setae; arms directed forward and somewhat divergent from each other; ventral plate in lateral view ( Fig. 67 F) with posterior margin serrated along basal two-thirds; ventral plate in caudal view ( Fig. 67 G) rounded ventrally, with lateral margin serrated along basal two-thirds, with numerous setae on posterior surface except both areas of dorsolateral corners bare. Median sclerite ( Fig. 67 F, H) plate-like, gradually widened from base toward near apex, with round apex, brown basally, but not sclerotized apically. Paramere ( Fig. 67 I) with several distinct hooks and several smaller ones. Aedeagal membrane ( Fig. 67 J) moderately covered with minute setae, and with moderately sclerotized dorsal plate in form of horizontal bar ( Fig. 67 K). Abdominal segment 10 ( Fig. 67 L, M) with four to eight hairs on lateral surface and one to three hairs on ventral surface on each side. Cercus ( Fig. 67 L, M) small, rounded, with seven to ten distinct hairs.

Pupa. Body length 2.0– 2.5 mm. Head. Integument including antennal sheaths yellow; frons moderately covered with tubercles, of which some or most having minute secondary projections, and with two pairs of unbranched short trichomes; face with pair of unbranched short trichomes slightly longer and stouter than frontal trichomes. Thorax. Integument yellow, moderately covered with tubercles, of which some on anterodorsal surface have minute secondary projections; thorax on each side with two short anterodorsal trichomes, two short anterolateral trichomes (one sometimes slightly thinner and shorter than other), one short mediolateral trichome, and three short ventrolateral trichomes (one slightly shorter and thinner than two others); all trichomes unbranched. Gill ( Fig. 68 A) with six slender thread-like filaments in three pairs (one dorsal, one middle and one ventral); no common basal stalk and basal fenestra small; all pairs short-stalked, and stalks of dorsal and ventral pairs lying at angle of 70 degrees when viewed laterally; filaments decreasing in length from dorsal to ventral, with longest dorsal filament 1.6–1.8 mm long and shortest ventral filament 1.1–1.5 mm long; relative thickness of filaments from dorsal to ventral when compared basally 1.0:0.9:0.9:0.8:0.9:0.7; all filaments medium brown, tapered toward basal half, then nearly of same thickness up to tip, with distinct annular ridges and furrows, and densely covered with minute tubercles. Abdomen. Dorsally, all segments unpigmented except segment 1, basal half of segment 2, and segment 9 light yellowish; segment 1 with one unbranched short seta on each side; segment 2 with one unbranched short seta and five spinous short setae on each side; segments 3 and 4, each with four distinct hooked spines and one unbranched spinous short seta on each side; segments 5 and 6 lacking spine-combs; segments 7–9 each with distinct spine-combs in transverse row and comb-like groups of minute spines on each side; segment 9 without terminal hooks. Ventrally, segments 4–8 unpigmented and segment 9 somewhat yellowish; segments 4–8 each with comb-like groups of minute spines; segment 4 with one unbranched stout hooklet and few slender minute setae on each side; segment 5 with pair of bifid stout hooks submedially and few unbranched short setae on each side; segments 6 and 7 each with pair of bifid inner and unbranched outer stout hooks somewhat separated from each other, and few unbranched short setae on each side. Grapnel-shaped hooklets absent on each side of segment 9. Cocoon. Wall-pocket-shaped, moderately woven, thin, ochreous, and not extended ventrolaterally; individual threads visible; 2.7–3.1 mm long by 1.0– 1.2 mm wide.

Mature larva. Body length 4.6–5.0 mm. Thoracic segment 1 and abdominal segments 1–4 each encircled by broad dark-gray transverse band and abdominal segments 5–9 dark gray on dorsal and dorsolateral surfaces; thoracic segments 2 and 3 often light gray on dorsal surface and dark gray on ventral surface, and abdominal segments 4–6 each with dark mediolongitudial band on ventral surface; abdominal segments 6 and 7 each with thin grayish transverse band ventrally. Head. Cephalic apotome yellow (though rarely dark yellow) with small medial area near posterior margin sometimes darkened; head spots almost indistinct or faintly positive. Lateral surface of head capsule yellow except eye-spot region whitish and areas anterior and posterior to eye-spot region somewhat darkened. Ventral surface of head capsule ( Fig. 68 D) yellow, though often widely darkened medially; long spot on each side of postgenal cleft clearly negative. Antenna composed of three articles and apical sensillum, slightly longer than stem of labral fan; length ratio of three articles (from base to tip) 1.0:0.9–1.0:0.7–0.8. Labral fan with 37–41 main rays. Mandible ( Fig. 68 B) with mandibular serrations composed of two teeth (one medium-sized, one small); main tooth at right angle against mandible on apical side; supernumerary serrations absent; comb-teeth decreasing in length from first to third. Hypostoma ( Fig. 68 C) with nine anterior teeth, of which corner teeth most prominent, slightly longer than median tooth, and intermediate teeth shortest; lateral margins serrate apically; four or five hypostomal bristles nearly parallel to lateral border on each side. Postgenal cleft ( Fig. 68 D) arrow-head shaped, long, 4.2–5.3 times length of postgenal bridge; subesophageal ganglion not pigmented. Cervical sclerite on each side composed of one medium-brown elongate piece and one light-brown elliptical piece, not fused to occiput. Thorax and Abdomen. Histoblast of pharate pupal gill with six short filaments. Thoracic and abdominal cuticle almost bare except few posterior segments moderately covered with colorless minute setae dorsally, and last segment of abdomen moderately covered with colorless short setae on each side of anal sclerite. Rectal scales present. Rectal organ compound, each lobe with 10–12 finger-like secondary lobules. Anal sclerite X-shaped, with short broad anterior arms 0.6–0.8 times as long as posterior ones; one or two sensilla on juncture area; five sensilla posterior to posterior arms. Last abdominal segment somewhat swollen laterally but lacking ventral papillae. Posterior circlet with 75–80 rows of hooklets with up to 15 or 16 hooklets per row.

Type material. HOLOTYPE: Female (with its associated pupal exuviae and cocoon) in 80% ethanol, labeled in a vial as [ UMSRP: Vietnam 0 45, Holotype, Simulium (S.) suoivangense , Female, coll. Vietnam, 24-IV-2014, Takaoka et al.], reared from a pupa collected from a river (width 4–6 m, water temperature 18.0˚C, exposed to the sun, elevation 1,452 m, 12˚10’56.408”N/108˚40’48.152”E), moderately flowing in open land, Suoi Vang , Lac Duong District , Lam Dong Province, southern Vietnam , 24-IV-2014, by H. Takaoka, M. Sofian-Azirun, Z. Ya’cob, C.D. Chen & K.W. Lau. PARATYPES: 11 females and five males and two mature larvae, same data as those of the holotype, labeled in each vial as [ UMSRP: Vietnam 0 45, Paratype, Simulium (S.) suoivangense , coll. Vietnam, 24- IV-2014, Takaoka et al.] ; 10 females and seven males (all reared from pupae) in 80% ethanol, labeled in each vial as [ UMSRP: Vietnam 0 45, Paratype, Simulium (S.) suoivangense , Male, coll. Vietnam, 9-XII-2015, Takaoka et al.], collected from a river (width 4–5 m, depth 20–30 cm, bottom of pebbles, water temperature 15.0˚C, partially shaded, elevation 223 m, 18˚58’03.270”N/104˚48’07.811”E), rapidly flowing in a natural forest, Pu Mat National Park , Nghe An Province, northern Vietnam , 9-XII-2015, by H. Takaoka, M. Sofian-Azirun, C.D. Chen & K.W. Lau.

Biological notes. The pupae and larvae of this new species were collected from leaves of trailing grasses and fallen tree leaves in the current. Associated species were S. (G.) asakoae and S. (S.) laui .

Distribution. Vietnam (Lam Dong and Nghe An).

Etymology. The species name suoivangense refers to the locality name, Suoi Vang, where this new species was collected.

Remarks. This new species is characterized by lacking pupal terminal hooks, differing from all 11 cytoforms and morphoform ‘a’ among S. (S.) tani (complex), all of which have pupal terminal hooks ( Takaoka et al. 2015a). It is also distinguished from cytoform ‘K’ (typical S. tani from Peninsular Malaysia) in the female by the relatively smaller size of the sensory vesicle to the third maxillary palpal segment (0.5 versus 0.6). The recognition of morphoform ‘b’ as a distinct species is supported by DNA sequence-based and chromosomal analyses (Adler et al. 2016; Low et al. 2016).

Figures

FIGURE 66. Female of Simulium (Simulium) suoivangense sp. nov. A, Third segment of maxillary palp with sensory vesicle (right side; front view); B, Cibarium (front view); C, Hind basitarsus and second tarsomere (left side; outer view). D, Sternite 8 and ovipositor valve (right side only; ventral view); E, Genital fork (ventral view); F & G, Paraprocts and cerci (F, ventral view; G, lateral view). H, Spermatheca. Scale bars. 0.1 mm for C; 0.02 mm for A, B and D – H.

FIGURE 67. Male of Simulium (Simulium) suoivangense sp. nov. A, Third segment of maxillary palp with sensory vesicle (right side; front view); B, Hind basitarsus and second tarsomere (left side; outer view); C, Coxites, styles and ventral plate (ventral view); D & E, Styles (right side; D, ventrolateral view; E, medial view); F, Ventral plate and median sclerite (lateral view); G, Ventral plate (caudal view); H, Median sclerite (caudal view); I, Paramere (left side; caudal view); J, Aedeagal membrane (caudal view); K, Dorsal plate (caudal view); L & M, Abdominal segment 10 and cerci (right side; L, lateral view; M, caudal view). Scale bars. 0.1 mm for B; 0.02 mm for A and C – M.

FIGURE 68. Pupa and larva of Simulium (Simulium) suoivangense sp. nov. A, Pupa; B – D, Larva. A, Anterior portion of thorax and gill filaments (left side; outer view); B, Mandible; C, Hypostoma; D, Head capsule (ventral view). Scale bars. 0.1 mm for A and D; 0.02 mm for B and C.