Simulium (Inaequalium) margaritatum Pepinelli, Hamada & Luz, 2006

Pepinelli, Mateus, Hamada, Neusa & Luz, Sérgio Luiz Bessa, 2006, Simulium (Inaequalium) margaritatum, a new species of black fly (Diptera: Simuliidae) from the central region of Bahia State, Brazil, Zootaxa 1167 (1), pp. 47-60 : 48-59

Simulium (Inaequalium) margaritatum Pepinelli, Hamada & Luz

( Figs. 1–42)

Description

FEMALE ( Figs. 1–13). General body color dark brown to black ( Figs. 1, 2). Body length 1.8–2.2 mm (n = 2); thorax lateral length 0.8 mm (n = 2); thorax dorsal length 0.8–0.9 mm (n = 2). Wing length 2.0 mm (n = 2); wing width 0.6–0.7 mm (n = 2).

Fronto­ocular triangle well developed ( Fig. 7). Frons, clypeus, and occiput black, with silver pruinosity. Antenna with silver pubescence, 0.37–0.39 mm (n = 4) in length; scape and pedicel light brown, remaining segments dark brown ( Fig. 5). Maxillary palpus dark brown; sensory vesicle elongated occupying more than 1/3 of length of palpomere III; palpomere V twice length of palpomeres III and IV ( Fig. 9). Mandible with 10 external serrations and 29–31 internal teeth. Lacinia with 26 or 27 retorse teeth. Cibarium with well developed, sclerotized cornuae, with teeth arranged over median elevation ( Fig. 3) [in 5 specimens we examined, 1 did not have central elevation ( Fig. 4)]. Thorax with scutum black covered by evenly arranged, recumbent, golden greenish hairs (and some reddish hairs), without pattern ( Fig. 1). Anepisternum and katepisternum dark brown with silver pruinosity. Scutellum dark brown with long dark setae and few golden setae. Postnotum with silver pruinosity. Costa of wing with spines and setae ( Fig. 6). Subcosta with sparse distribution of setae ( Fig. 6). Basal section of radius bare; R1 with spines and setae; Rs with setae. Leg coloration as in male, except hind leg with basitarsus proximal 2/3 whitish and distal 1/3 dark brown. Claws curved, with basal tooth ( Fig. 8). Abdominal tergite II with silver pruinosity on anterolateral margins ( Fig. 2). Tergite plates II–IX with varnishlike appearance. Basal fringe with long, golden hairs. Sternites grayish brown; genitalia dark brown. Eighth sternite weakly sclerotized with evenly distributed setae; hypogynial valves (= gonapophyses) subtriangular, without microtrichia and membranous, except weakly sclerotized on internal margins ( Fig. 13). Cercus rounded, covered with small hairs and long brown setae; anal lobe (= paraproct) short, with small protuberance near cercus ( Fig. 12). Genital fork stout, sclerotized with distal end of stem weakly expanded; lateral arms well developed, with large anterior process; lateral arms forming suboval space ( Fig. 10). Spermatheca globular, with internal spicules arranged in groups ( Fig. 11); spermathecal duct unpigmented.

MALE ( Figs. 14–26). General body color dark brown ( Figs. 14–16). Body length 2.2 mm (n = 1); thorax lateral length 0.83 mm (n = 1); thorax dorsal length 0.78 mm (n = 1). Wing length 1.8 mm (n = 1); wing width 1.3 mm (n = 1).

Antennae with silver pubescence, 0.42–0.47 mm (n = 4) in length; scape and pedicel brown, remaining segments dark brown. Palpus dark brown, sensory vesicle small, occupying less than 1/5 of palpomere III; palpomere V about 2.3 times as long as palpomeres III and IV ( Fig. 19). Scutum black covered with golden hairs. Scutal pattern varies with light incidence: with anterior light source, scutum black with 1 + 1 anterolateral rounded, well­defined silver spot ( Fig. 14); with posterior light source, scutum black ( Fig. 15). Lateral and posterior margins of scutum pruinose ( Fig. 16). Scutellum dark brown with long, black hairs and short, sparse, golden hairs. Postnotum with silver pruinosity. Anepisternum and katepisternum dark brown with silver pruinosity. Costa of wing with spines and setae ( Fig. 18). Subcosta bare ( Fig. 18). Basal section of radius bare ( Fig. 18); R1 with spines; Rs with setae. Leg coloration and proportions as in Figs. 20, 21. Fore leg with coxa, trochanter, and femur dark brown, tibiae with anterior region whitish and posterior brown, basitarsus and tarsomeres I–IV dark brown ( Fig. 20). Middle leg with coxa, trochanter, and femur dark brown, proximal 1/3 of tibia whitish and distal 2/3 dark brown, more than half of proximal region of basitarsus whitish, remaining dark brown and tarsomeres I–IV dark brown ( Fig. 21). Hind leg with coxa, trochanter, and femur dark brown, proximal 2/3 of tibia dark brown and distal 1/3 whitish, proximal 3/4 of basitarsus whitish and distal 1/4 dark brown, tarsomeres I–IV dark brown ( Fig. 22). Claws without basal tooth, but with well­developed thumblike lobe ( Fig. 17). Calcipala reaching pedisulcus. Femur and tibia of middle and hind leg with scalelike setae distributed among filiform ones. Abdominal tergites ( Fig. 16) black; basal fringe with long, thin, blackgolden hairs; tergite II black with silver pruinosity; tergite III without silver pruinosity; tergites IV–VII with silver pruinosity on laterodorsal edge. Abdominal sternites membranous. Sternites III–VIII with silver pruinosity on median region. Genitalia dark brown; gonocoxite and gonostylus covered with small hairs and long setae; gonocoxite subquadrangular ( Fig. 23); gonostylus subtrapezoidal ( Fig. 23), nearly as long as gonocoxite at mid point, with 1 subterminal spine. Ventral plate elongated, covered by long hairs, as in Fig. 26. Median sclerite Y shaped ( Fig. 25). Paramere with developed and sclerotized basal process and numerous stout teeth ( Fig. 24).

PUPA ( Figs. 27–34). Cocoon length dorsally 2.4–2.7 mm (mean = 2.5 mm, SD = 0.13, n = 5), ventrally 3.0– 3.3 mm (mean = 3.1 mm, SD = 0.15, n = 5); pupa lateral length 2.1–2.6 mm (mean = 2.3 mm; SD = 0.22, n = 5).

Cocoon slipper shaped, light brown, composed of thick coalesced fibers with short dorsal projection ( Figs. 27, 30). Cephalic plate with 2 + 2 long, bifid or trifid frontal and 1 + 1 bifid dorsal trichomes; tubercles rounded, densely distributed over entire cephalic plate ( Figs. 29, 32). Thorax with 5 pairs of long trichomes, each with 3–8 ramifications ( Fig. 28), near edge of dorsal cleft; tubercles rounded, sometimes acuminated, densely distributed over entire surface; on anterior region, tubercles bigger than on posterior region. Gill length 3.2–3.7 mm (mean = 3.4 mm, SD = 0.22, n = 5) pale brownish. Gill with 4 forwardly directed filaments, with main trunk short, giving rise to 2 short sets of primary branches that bifurcate near gill base into 2 secondary branches each consisting of 2 filaments ( Fig. 31). All gill filaments approximately same length ( Fig. 27), with rounded ends ( Fig. 31). Abdominal tergites as in Figs. 33a–d. Tergite I with 1 + 1 filiform setae and 2 + 2 submedian short, strong setae. Tergite II with 3 + 3 submedian simple or bifid trichomes and 3 + 3 short setae on lateral region near external trichome ( Fig. 33a). Tergites III–IV with 4 + 4 submedian simple or bifid hooks ( Fig. 33b). Tergites V–IX with spine combs on anterior edge ( Figs. 33c–d). Tergites II–IX with 1–5 submedian simple trichomes and 1–3 simple trichomes on lateral margin; tergite IX weakly sclerotized. Abdominal sternites as in Figs. 34a–c. Sternites III–IV with spine combs on anterior edge. Sternite V with 2 + 2 close, bifid hooks in row and 2 + 2 simple trichomes on lateral margin ( Fig. 34a). Sternite VI–VII with 2 + 2 simple or bifid hooks and 2 + 2 simple, small trichomes near hooks ( Fig. 34b). Sternite VIII without hooks. Abdominal sternites III–VIII with spine combs on anterior edge ( Fig. 34c).

LARVA (last instar) ( Figs. 35–42). Body length: 4.9–5.3 mm (mean = 5.1 mm, SD = 0.2, n = 5); lateral length of head capsule: 0.64–0.69 mm (mean = 0.66 mm, SD = 0.02, n = 5); dorsal width of head capsule: 0.52–0.56 mm (mean = 0.54 mm, SD = 0.02, n = 5).

General body coloration light to dark gray (in Carnoy’s solution). Head pale to dark brown with positive pattern ( Fig. 35); cuticle of dorsal and ventral region with small, simple setae. Cervical sclerites small, free in membrane. Postgenal cleft narrow, subtriangular ( Figs. 36, 37). Postgenal bridge 0.7 times as long as hypostoma ( Fig. 37). Hypostoma with strongly pigmented anterior edge and 9 apical teeth ( Fig. 39): median tooth simple and more prominent than sublateral teeth, 3 + 3 rows of sublateral teeth, middle tooth smaller than remaining teeth, 2 poorly developed paralateral teeth, and 6 or 7 small lateral serrations; hypostoma with 1 + 1 line of 5 or 6 lateral setae parallel to lateral edge and 1 + 1 long and 1 + 1 or 2 + 2 short setae in posterior region of hypostoma near hypostomal groove. Subesophageal ganglion pigmented ( Fig. 36). Antenna as long as labral fan stalk; antennal articles pale brown, except distal article, which is darker than proximal and medial articles ( Fig. 41); segment proportions (proximal, medial, distal) approximately 0.9–1.0:0.7–0.8:1.3–1.4 (n = 2). Mandible with 3 apical teeth, 10 internal teeth, 1 large mandibular serration, 1 small mandibular sensillum (sensu Craig & Craig 1986) and 1–2 lateral mandibular processes thick and longer than mandible edge ( Fig. 38). Cephalic fan with 44–48 rays. Thorax gray dorsally and ventrally. Gill histoblast dissected, with 4 filaments. Abdomen usually completely grey dorsally, progressively paler ventrally, posterior region whitish ventrally; faint segmental banding visible dorsally ( Fig. 40). Ventral nerve cord dark grey. Ventral tubercles small, subtriangular. Anterodorsal arms of anal sclerite shorter in length than posteroventral arms ( Fig. 42). Posterior proleg bearing approximately 80 rows of up to 12 or 13 hooks (n = 2). Anal papillae with 3 branches, each with approximately 5 or 6 fingerlike lobes of same length (n = 2).

Taxonomic Discussion

Simulium margaritatum n. sp. is placed in the subgenus Inaequalium , based on the combination of characters given by Coscarón & Wygodzinsky (1984). This new species might be included in the inaequale species group because it has males with the gonostylus subtrapezoidal, pupae with filiform gill filaments, larvae with the postgenal cleft narrow and subtriangular, and the postgenal bridge 0.7 times as long as the hypostoma ( Coscarón 1987). However, males of this new species have the ventral plate longer than wide, as in species of the S. botulibranchium group. According to Coscarón (1987), the females of the species in the subgenus Inaequalium are difficult to separate, whereas the pupae are the best stage to distinguish the species. The female of S. margaritatum n. sp. differs from most known females of the inaequale group by the unpatterned scutum ( Fig. 1). The female scutum of the new species is similar to that of S. petropoliense Coscarón , which also has no pattern, but the latter species has the scutum more densely covered with hairs than does S. margaritatum n. sp. The anal lobe of S. margaritatum n. sp. has a small protuberance near the cercus ( Fig. 12); this structure can be used to distinguish this species from some species in the subgenus Inaequalium . Variation was observed in the female cibarium of the new species. One of the five specimens we examined did not have the central region of the cibarium protuberant, which is typical of species of Inaequalium ( Figs. 3, 4). This variant could be the result of some abnormality; more specimens will need to be examined to verify our finding. Based on the original description ( Pessoa et al. 2005), the female of S. maranguapense also lacks the typical central elevation in the cibarium. Males of several species in the subgenus Inaequalium have a pair of rounded silver spots on the anterolateral area of the scutum, but the edges of these spots are not as well defined as the ones of the new species ( Fig. 14). Also, males of the new species can be distinguished from the other species by the structure of the gonostylus and ventral plate ( Figs. 23, 26). They also can be recognized by the configuration and number of gill filaments ( Figs. 27, 31). The pupa of the new species has a gill with four filiform filaments, which distinguishes it from almost all other species in the subgenus Inaequalium . Simulium maranguapense also has a gill with four filaments, but the filaments are distinctly inflated ( Pessoa et al. 2005). The larva of S. margaritatum n. sp. has a pigmented subesophageal ganglion ( Fig. 36), which distinguishes it from the larvae of S. clavibranchium Lutz , S. diversibranchium Lutz , S. inaequale (Paterson & Shannon) , S. leopoldense (Strieder & Py­Daniel) , S. nahimi Py­Daniel , S. maranguapense , S. nogueirai D’Andretta & González , S. rappae Py­Daniel & Coscarón , S. subclavibranchium Lutz , S. subnigrum Lutz , and S. travassosi D’Andretta & D’Andretta. Larvae of S. botulibranchium Lutz and S. petropoliense also have a pigmented subesophageal ganglion, but can be distinguished by the shape of the postgenal cleft, which is shallower than in S. margaritatum n. sp. For the remaining species of the subgenus Inaequalium , we do not have information about the pigmentation of the subesophageal ganglion. The larvae of S. margaritatum n. sp. also can be distinguished from other species in this subgenus with known larvae by the number and configuration of the gill filaments, after dissection of the gill histoblast.

Etymology

The name of this new species is derived from Latin and means “adorned with pearls”, in reference to the two well­defined, silver spots, located on the anterolateral region of the male scutum.

Distribution

Simulium margaritatum n. sp. has been collected only in the central region of Bahia State, Brazil, in the Chapada Diamantina National Park and surrounding area (see Material Examined).

Bionomics

Larvae and pupae were collected in six small, rock­bottomed streams in open areas, exposed to sunlight, usually in areas with a thin layer of water and low water velocity. The width of these streams varied from 0.2 to 1.5 m (mean = 0.7 m, SD = 0.55). The streams were located at altitudes from 770 to 1683 m. For substrate, larvae and pupae used trailing vegetation, deciduous leaves, and rocks. The streams had a mean water temperature of 19 o C (SD = 3.8), electrical conductivity from 20 to less than 40 µS/cm, and a mean pH of 4.2 (SD = 0.2). Females did not bite humans during the field work.

Material examined

Holotype ( INPA). Brazil, Bahia State, Itaitê Municipality. Rumo village, Chapadinha, small tributary of the Urubu River (#25), 13 o 11’S 41 o 10’W, 29.vii.2005 (N Hamada, M Pepinelli) – 1 male (pinned), with pupal exuviae in glycerine.

Paratypes. Brazil, Bahia State, Piatã Municipality. Serra dos Barbados: Córrego Forquilha (#47), 13 o 17’S 41 o 54’W, 06.viii.2005 (N Hamada, M Pepinelli and VL Landeiro) – 5 larvae (L), 5 pupae (P), 1 male (M), with pupal exuviae in glycerine ( INPA) .

Palmeiras Municipality. Parque Nacional Chapada Diamantina : small stream that cross the trail to Cachoeira da Fumaça (#34), 12 o 36’S 41 o 27’W, 31.vii.2005 (N Hamada, M Pepinelli & VL Landeiro) – 1M, 1 female (F) with pupal exuviae in glycerine, 5P, 5L ( MZUSP); small stream that cross the trail to Cachoeira da Fumaça (#35) 12 o 36’S 41 o 27’W, 31.vii.2005 (N Hamada, M Pepinelli & VL Landeiro) – 2M, 1F, 5P, 5L ( INPA) .

Itaitê Municipality. Urubu River (#24), Chapadinha, Rumo village , 13 o 11’S 41 o 10’W, 29.vii.2005 (N Hamada, M Pepinelli) – 5P, 5L ( INPA) ; small tributary of Urubu River (#25), Chapadinha, Rumo village , 13 o 11’S 41 o 10’W, 29.vii.2005 (N Hamada, M Pepinelli) – 5P, 5L, 2F ( INPA) . Rio de Contas Municipality. (#57), first stream in the trail to Mocotó waterfall, Mato Grosso village, 13 o 25’S 41 o 50’W, 10.viii.2005 (N Hamada, M Pepinelli & VL Landeiro) – 1F ( INPA) .

Other material examined Simulium inaequale . Brazil, São Paulo state, Botucatu Municipality (#13), 22 o 54’S

48 o 23’W, 11.v.2004 (N Hamada, M Pepinelli) – 2 last­instar larvae in ethanol ( INPA). Simulium clavibranchium . Brazil, São Paulo state, São José do Barreiro Municipality

(#19), 22 o 46’S 44 o 31’W 14.v.2004 (N Hamada, M Pepinelli) – 5 last­instar larvae in ethanol ( INPA) .

Simulium subclavibranchium . Brazil, Minas Gerais state, Camanducaia Municipality, Monte Verde district (#45), 22 o 52’S 46 o 02’W, 23.v.2004 (N Hamada, M Pepinelli) – 2 lastinstar larvae in ethanol ( INPA) .

Simulium subnigrum . Brazil, Rio Grande do Sul state, Sapiranga Municipality (#4), 05 o 02’S 67 o 27’W, 03.xi.2005 (N Hamada) – 2 last­instar larvae in ethanol ( INPA) .

Simulium rappae . Brazil, São Paulo state, Brotas Municipality (#8), 22 o 16’S 48 o 11’W, 10.v.2004 (N Hamada, M Pepinelli) – 2 last­instar larvae in ethanol ( INPA) .

Simulium nogueirai . Brazil, São Paulo state, São José do Barreiro Municipality (#19), 22 o 46’S 44 o 31’W, 14.v.2004 (N Hamada, M Pepinelli) – 5 last­instar larvae in ethanol ( INPA) .

Simulium diversibranchium . Brazil, São Paulo state, Campos do Jordão Municipality, Parque Estadual Campos do Jordão (#34), 22 o 39’S 45 o 27’W, 18.v.2004 (N Hamada, M Pepinelli) – 1 last­instar larva in ethanol ( INPA) .

Simulium travassosi . Brazil, São Paulo state, Botucatu Municipality (#13), 22 o 54’S 48 o 23’W, 11.v.2004 (N Hamada, M Pepinelli) – 1 last­instar larva in ethanol ( INPA) .

Simulium botulibranchium . Brazil, Minas Gerais state, Camanducaia Municipality, Monte Verde district (#45), 22 o 52’S 46 o 02’W, 23.v.2004 (N Hamada, M Pepinelli) – 2 lastinstar larvae in ethanol ( INPA) .

Simulium petropoliense . Brazil, Rio de Janeiro state, Petrópolis Municipality (#14), 22 o 27’S 43 o 06’W, 14.ix.2005 (N Hamada, M Pepinelli) – 5 last­instar larvae in ethanol, 3 pinned females with pupal exuviae in glycerine ( INPA) .

Simulium nahimi . Brazil, Rondônia, Vilhena Municipality, small stream on the road to Usina do Rio Vermelho (#34), 12 o 53’S 60 o 11’W, 25.vii.2004, (N Hamada) – 2 last­instar larvae in ethanol ( INPA) .