Macropelopia multifasciata, Dantas & Siri & Hamada, 2023

Dantas, Galileu P. S., Siri, Augusto & Hamada, Neusa, 2023, A new species of Macropelopia Thienemann, 1916 (Diptera: Chironomidae) from Southern Brazil, Zootaxa 5306 (5), pp. 551-562 : 552-561

Macropelopia multifasciata sp. nov.

Type material. Holotype male with pupal and larval exuviae, BRAZIL: Rio Grande do Sul, S„o Francisco de Paula, FLONA S„o Francisco de Paula , Arroio dos Pinheiros Centenários, 29°25’13.4’’ S, 50°23’40.4’’ W, 878 m a.s.l., 02.ix.2015, leg. G.P.S. Dantas ( INPA) . Paratypes, 1 male with pupal and larval exuviae ( INPA) ; 1 female with pupal and larval exuviae ( INPA); all with the same data as holotype .

Etymology. Derived from the Latin multi, meaning “many,” and fasciata, meaning “spot,” an allusion to the dark spots on the tibiae of the new species.

Diagnostic characters. Male — Wing membrane pale brown, with dark-brown spots; tibiae banded; R 3 reaching costa; dorsal tubercle well-developed, inner verticals uniserial; fore tibia with a long and strong pre-apical comb-like bristles, similar to the comb of the hind tibia; gonostylus with an internal lobe, with tubercles bearing setae; tergite IX with 16–20 posterior setae. Female —Wing membrane pale brown, with dark-brown spots; AR 0.17; tibiae with several dark-brown bands. Pupa— Dorsocentrals (Dc 1 and Dc 2) sclerotized and granular in apical ½; supraalar (Sa) filamentous, slightly longer than Dc 2. Thoracic horn large, flattish, narrow basally and expanded apically, arising from a small tubercle, outer margin strongly convex, inner margin more-or-less straight, external membrane with few spines, horn sac with narrow internal supporting rods, filling the entire lumen, connected directly to the plastron plate; plastron plate flattened, expanded laterally, occupying the width of the horn apex. Larva — SSm, S5, S7 and S10 multi-branched; S8 and S9 slender and simple. Maxillary palp with ring organ distalmost. Mandible with ventrolateral seta 1 simple, 2 and 3 bifurcated. Dorsomentum with 4 teeth on each side. Pseudoradula weakly granulose apically; labial vesicles well developed and rounded. Ligula with five teeth, anterior row of teeth slightly concave, tips of the inner teeth distinctly curved outwardly. Paraligula bifid. Posterior parapod apex with about 12 simple claws, arising from a sclerotized concave plate.

Description. Adult male (n= 2). Total length 4.00– 4.08 mm. Wing length 2.06 mm. Total length/wing length 1.98. Wing length/length of profemur 1.96.

Coloration: Head, maxillary palp, and antenna brown. Thorax with general coloration brown, darker in vittae, postnotum and preepisternum. Wing membrane pale brown, with dark-brown spots and covered with microtrichia ( Fig. 1C ). Legs: all femurs brown, with a pre-apical dark-brown band; fore tibia pale, with two complete and six incomplete bands; mid tibia pale, with two complete and five incomplete bands; hind tibia pale, with two complete and four incomplete bands; ta 1 –ta 5 pale ( Fig. 3 ). Abdomen brownish, tergites VI–VIII darker.

Head ( Fig. 2A ). AR 1.51. Antenna with 14 flagellomeres; penultimate flagellomere 610 μm long. Apical flagellomere not offset, 76 μm long, 27 μm wide at base; with a subapical seta 60 μm long. Eyes with small fine setae, restricted to internal margins; dorsomedial extension well developed, 125–130 µm long, 85–93 µm wide, medially separated by 92–100 µm. Temporal setae 19–29, uniserial anteriorly and multiserial posteriorly. Clypeus 103–108 μm long, 90–100 μm wide, with 8–16 setae. Cibarial pump with anterior margin concave, 210–225 μm long and with orifice 126 from apex. Tentorium 214–226 μm long. Palpomere lengths (1–5 in μm): 43–49; 51–60; 106–110; 175–178; 203–257.

Thorax ( Fig. 2B ). Scutal tubercle well developed, 55–60 µm wide at base, 85–90 µm long.Acrostichals about 60; dorsocentrals 29–30, bi- to multiserial anteriorly, uniserial posteriorly; prealars 21–25; supraalars 1. Antepronotum with 10–13 lateral setae, placed near the base of antepronotum. Scutellum with about 20 setae. Postnotum with 8–10 setae. Preepisternals 1–2; anepisternals 1–2.

Wing ( Fig. 2C ). Width 0.63 mm. Membrane covered with macrotrichia; Costa 2.16 mm long, produced beyond apex of R 4+5 by 185 μm. R 2+3 distinct, R 2 present, R 3 reaching costa. MCu slightly proximal to the RM. Brachiolum with 8 setae. Squama with 32 setae. Anal lobe well developed. VR 0.95. WW 0.31.

Legs ( Figs. 3A–D ). Foretibia 65 μm wide at apex, with one apical, pectinate spur, 61 μm long, bearing 17 lateral teeth; 6 strong preapical bristles similar to a comb ( Fig. 3D ), about 150 μm long. Mid tibia 63 μm wide at apex, with two apical pectinate spurs, 60 and 70 μm long, bearing 14 and 18 lateral teeth, respectively. Hind tibia 66 μm wide at apex, with two apical pectinate spurs, 65 and 85 μm long, bearing 14 lateral teeth in short spur; tibial comb with 7 bristles. Claws slender, distally pointed and spinulate on the basal 1/3. Pulvilli well developed. Lengths (in μm) and proportions of leg segments as in Table 1 .

Hypopygium ( Fig. 2D ). Tergite IX with 16–20 posterior setae. Anal point rounded. Phallapodeme slender, 38– 44 μm long. Sternapodeme slender, without anterior process. Gonocoxite subcylindrical, 155–160 μm long, 75–87 μm wide, with a dorsal lobe-like setigerous swelling. Inferior volsella absent. Gonostylus broad basally, tapered and curved at apex, 102–105 μm long, with 6 setae on the inner margin, 4 of which are placed in a small median lobe; megaseta 8–9 μm long. HR 1.52; HV 3.92.

Adult female (n= 1). Total length 2.61 mm. Wing length 1.94 mm. Total length/ wing length 1.34. Wing length/ length of profemur 2.14.

Coloration. Head, maxillary palp, and antenna brown. Thorax with general coloration brown, darker in vitae and postnotum. Wing membrane pale brown, with dark-brown spots and covered with macrotrichia. Legs: femurs brown, with a pre-apical dark-brown band; fore tibia pale, with 7 dark-brown bands; mid and hind tibiae pale, with 6 dark-brown bands; ta 1 –ta 5 pale. Abdomen brownish.

Head. AR 0.17. Antenna with 14 flagellomeres; apical flagellomere 88 µm long; 34 µm wide, with an apical seta 54 µm long; pedicel with 15 setae; scape with 5 setae. Eyes bare; dorsomedial extension 95 µm long, 103 µm wide, medially separated by 117 µm. Temporal setae about 30, multiserial. Clypeus 113 µm long, 101 µm wide, with 15 setae. Cibarial pump with anterior margin concave, 225 μm long, and with orifice 57 μm from apex. Tentorium 204 μm long. Palpomere lengths (1–5 in µm): 45; 64; 107; 166; 243.

Thorax. Scutal tubercle well developed, 56 µm wide at base, 78 µm long; medial scar absent. Acrostichals uncountable; dorsocentrals 43, multiserial anteriorly, uniserial posteriorly; prealars 22; supraalars 1. Antepronotum with 6–8 lateral setae, tubercle absent. Scutellum covered with setae of varying sizes. Postnotum with 8 dorsal setae. Preepisternals 1; anepisternals 1.

Wing. Width 0.68 mm. Membrane with covering of macrotrichia; Costa 1.96 mm long, produced beyond apex of R 4+5 by 141 μm. R 2+3 distinct, R 2 present, R 3 reaching costa. MCu slightly proximal to the RM. Brachiolum with 10 setae. Squama with 35 setae. Anal lobe weakly developed. VR 0.91. WW 0.35.

Legs. Foretibia 60 μm wide at apex, with one apical, pectinate spur, 52 μm long, bearing 14 lateral teeth; comb not observed. Mid tibia 62 μm wide at apex, with two apical, pectinate spurs, 58 and 60 μm long, bearing 10 and 14 lateral teeth, respectively. Hind tibia 67 μm wide at apex, with two apical, pectinate spurs, 55 and 75 μm long, bearing several lateral teeth; tibial comb with 7 bristles. Claws slender, distally pointed and spinulate on the basal 1/3. Pulvilli well developed. Lengths (in μm) and proportions of leg segments as in Table 2 .

Genitalia ( Fig. 2E ). Tergite IX without setae. Three balloon-shaped seminal capsules, with 70 µm long; spermathecal ducts annulate, separated for their entire lengths. Gonapophysis VIII covered with setae, not touching medially. Coxosternapodeme strongly curved, 95 μm long. Tergite X 150 μm wide, covered by microtrichia, with about 3 setae on each side; posterior margin biconcave. Notum 152 μm long, Ra (ramus) elongates, 75 µm long. Cercus 52 µm long.

Pupa (n= 3). Total length 5.03 mm (abdomen and thorax).

Coloration. Cephalothorax brownish, thorax and wing sheath uniform pale brown ( Fig. 4C ); thoracic horn and plastron plate brown ( Fig. 4A ). Abdomen brownish; anal lobe mostly pale, light brown at the base and outer margin, with a large central light-brown spot on each side ( Fig. 4E ).

Cephalothorax. Thorax with anterior field of fine shagreen, dorsal surface striated. Precorneal setae (Pc) filamentous and distally pointed, 48 μm long, with a small accessory basal seta apically blunt, 20 μm long. Dorsocentrals (Dc 1 and Dc 2) sclerotized and granular in apical ½ ( Fig. 4B ), Dc 1 90–97 μm long, Dc 2 77–85 μm long. Supraalar (Sa) filamentous, slightly longer than Dc 2. Frontal apotome somewhat triangular. Wing sheath smooth, strongly expanded in the distal half, 1.35–1.41 mm long and maximum width 0.54–0.57 mm. Thoracic horn large, flattish, narrow basally and expanded apically, arising from a small tubercle, outer margin strongly convex, inner margin more-or-less straight ( Fig. 4A ), 471–487 μm long and maximum width 230–272 μm; external membrane with reticulate pattern and few spines, horn sac with narrow internal supporting rods, filling the entire lumen, connected directly to the plastron plate; plastron plate flattened, expanded laterally, occupying the horn apex, 56–60 μm long, 210–233 μm wide. Basal lobe and thoracic comb absent.

Abdomen ( Fig. 4E ). Tergite I with a distinct and elongate scar, 130 μm long ( Fig. 4D ). Spines of abdominal shagreen solitary or in groups of 2–4, serially arranged. Tergites I–VIII with large field of shagreen composed of short spinules arranged in transverse rows (in the medial-posterior region of TVII–VIII the spinules are scattered); anal lobe with fine shagreen. Sternites VII–VIII with large field of shagreen composed of short spinules arranged in transverse rows. Tergite I with 2 L setae on each side; T II–VI with 1 L setae on each side; TVII with 5 relatively shorts LS setae, about 200 μm long, placed on the posterior 1/3 of the segment ( Fig. 4E ). T VIII with 5 lateral filaments, placed on the distal 2/3 of the segment.Abdominal setation: D 1 enlarged, arising from a chitinised tubercle on segments II–VII; D 2 and D 3 on segments III–V filamentous and elongate, arising from rounded, protruding tubercles; D 4 and D 5 smaller and filamentous. Anal lobe as in Figure 4E , 870 μm long, 608 μm wide at base, with 2 lateral macrosetae; outer border with a fringe of about 35 filaments along most of the edge but spinose distally (with about 18 spines); inner border spinose in the distal ½ (with about 20 spines). Genital sac small, wedge-shaped, 267 μm long, 233 μm wide at base. GS/AL 0.31.

Larva (n= 3).

Coloration. Head yellow; postoccipital margin dark brown; apex of mandible and of ligula dark. Abdomen strongly red (in live larvae); procercus half pale and half light brown; anal setae brown. All posterior parapod claws light brown.

Head ( Fig. 5A ). Head capsule oval; cephalic index 1.03. Chaetotaxy as in Figure 5 B-C. Dorsally S7 aligned lateral to slightly antero-lateral to S8; S5 far anterodorsal, DP posterior, unaligned with S7, S8. Ventrally SSm lies medially to the rather closely approximated S9 and S10; VP distantly posterolateral. SSm, S5, S7 and S10 multi-branched; S8 and S9 slender and simple.

Antenna ( Fig. 6A ). Length 182–187 μm, A 1 154–160 μm long, 28–30 μm wide, with ring organ placed 120 μm from base, A 2 19–20 μm long. AR 5.50. Blade 27–29 μm long, reaching the flagellum apex; accessory blade not reaching the apex of A 2.

Maxilla ( Fig. 6B ). Basal palp segment 31 μm long and 14 μm wide, with ring organ distalmost, placed 15 μm from base. Length of A 1 /P 1 5.87, of A 2 /P 1 0.65.

Mandible ( Fig. 6C ). Slender, moderately curved. Length 120–122 μm, with 3 lateral setae and 1 sensilla; ventrolateral seta 1 simple, 2 and 3 bifurcated. Molar projection apically pointed; inner margin of molar without tooth-like points; seta subdentalis 32 μm long. A 1 /Md 1.28–1.31.

Mentum and M appendage ( Figs. 6D–E ). Dorsomentum with 4 large teeth and 1 minute tooth on each side, labial vesicles well developed, rounded. M appendage broadly sagittate, bluntly rounded apically; pseudoradula 67–80 μm long, weakly granulose apically.

Hypopharyngeal complex ( Fig. 6F ). Ligula with five teeth, anterior row of teeth slightly concave; 70–86 μm long, 43–48, 36–39 and 46–55 μm wide at apex, middle and base respectively; tips of the inner teeth curved outwardly. Paraligula bifid, 42–48 μm long, inner tooth about 4× shorter than outer tooth. Pecten hypopharyngis with about 20 teeth.

Body. With lateral fringe of swim-setae. Anterior parapods small, with simple claws. Posterior parapod apex with about 12 simple claws, some serrated on inner margins, most arising from a sclerotized concave plate ( Fig. 5E ). Subbasal seta of posterior parapod simple, 225–250 μm long. Procercus 200–210 μm long, 44–50 μm wide; with 14 anal setae, 595–632 μm long; with a smaller preapical seta, 67–70 μm long and a small basal multi-branched seta, 35–40 μm long ( Fig. 5D ). L/W 4.20–4.55. Supraanal setae 460 μm long. Anal tubules not observed.

Distribution and bionomics. The species is known only from the type locality in southern Brazil. Larvae were collected associated with fine sediments of a first-order stream ( Fig. 1 ).

Taxonomic remarks. Since its erection and subsequent revisions, the Macropelopiini tribe has been defined by a combination of characters from all semaphoronts. The combination of characters of the species described here does not fit into any of the known genera of Macropelopiini . However, we consider that due to presence of a well-developed scutal tubercle in the male adult and the absence of an inner fringe on the anal lobe of the pupa, the new species belong to Macropelopia . Although the adult male of the genus Bilyjomyia has a scutal tubercle, it is greatly reduced.

The male adults of the two known species of Macropelopia from the Neotropics, M. chilensis and M. patagonica , lack the typical comb formed by short, clear spines on the front tibia, which are present in most species of the genus (see Fig. 34, p. 109 in Fittkau 1962) as well as in Alotanypus (see Fig. 3 , p. 57 in Siri et al. 2011) and Paggipelopia . However, Silva & Pinho (2018) have identified a series of thick setae located subapically on the front tibia of M. patagonica , which they consider homologous to the tibial comb on the forelegs formed by small spines in other Macropelopia species. A similar structure occurs on the front tibia of M. multifasciata sp. nov. ( Fig. 3D ), but we avoid considering it a true tibial comb or even homologous to the typical front tibial comb found in other members of Macropelopia , due to the great difference in shape, size, quantity, and position/distribution of these structures. The male adult of the new species can be distinguished from M. patagonica by having wing membrane with darkbrown spots, R 3 reaching costa and gonostylus with an internal lobe, with tubercles bearing setae. In addition, the color pattern of the legs of the new species appears to be unique among members of Macropelopia .

Based mainly on pupal characteristics, M. ( Macropelopia ) has been divided into two species groups, notata and nebulosa. According to the pupa of the new species, it could be placed in the notata group by having a scar on tergite I, elongate D 2 and D 3 setae on segments II–V, and 5 LS on segment VIII. The pupae of the new species can be keyed out in Macropelopia in the key to identifying pupae of Tanypodinae provided by Fittkau & Murray (1986); however, the new species has some characteristics that conflict with the generic diagnosis. According to the concept of Macropelopia in Fittkau (1962) and Fittkau & Murray (1986), pupae have Dc 2 minute (0.1× as long as Dc 1), an oval, circular or triangular plastron and the scar in TI (when present) is roundish. However, pupae of M. multifasciata sp. nov. have Dc 2 similar to Dc 1 in size and shape, flattened plastron plate and TI with an elongated scar.

In the keys of the Holarctic Chironomidae ( Cranston & Epler 2013) , the larva of M. multifasciata sp. nov. will key partially to Brundiniella by tooth-row of ligula moderately concave, but it is inconsistent with dorsomental plates produced into points, almost reaching to pseudoradula and one claw of posterior parapod basally widened found in Brundiniella . If the tooth-row of ligula is not considered, the larva of the new species keys to couplet 14 ( Apsectrotanypus and Macropelopia ) but does not fit either alternative. In the key to Neotropical Chironomidae larvae (Silva et al. 2018), M. multifasciata sp. nov. will key to the monotypic genus Paggipelopia Siri & Donato. However , ligula wide at base and with anterior row of teeth slightly concave; mandible with molar projection well developed, antennal blade not extending beyond apex of flagellum, accessory blade not reaching the apex of segment 2, and the distal position of the ring organ on the maxillary palp, distinguish the new species from P. spaccesii Siri & Donato.

The incongruity observed in the larva of M. multifasciata sp. nov. with the diagnostic characteristics of the genus raises important questions. One possibility is that this discrepancy may result from a lack of information about the larvae of other species within the genus. Alternatively, the many differences found in the larva of the new species may reflect local adaptations, since the larval stage is particularly susceptible to environmental pressures and may involve complex interactions with the environment.

In general, Macropelopia presents a considerable challenge to taxonomists, mainly due to inadequate descriptions and illustrations of many of its species, as well as limited knowledge of its distribution. These factors make it difficult to accurately identify new species within the genus. Furthermore, the inclusion of Neotropical species in Macropelopia adds more complexity to its classification, as they do not fit well with the current concept of the genus, which is based mainly on Holarctic species. Therefore, to improve the taxonomic classification of Macropelopia , in addition to a taxonomic revision, it is essential to carry out comprehensive studies that cover a wider range of species and geographical locations. Such efforts will ultimately promote a better understanding of the diversity and complexity of this fascinating group of insects.

Figures

FIGURE 1. Environment where the immature stages of M. multifasciata sp. nov. were collected.

FIGURE 2. Macropelopia multifasciata sp. nov. Adult male, (A) Head. (B) Thorax. (C) Wing. (D) Hypopygium.Adult female, (E) Genitalia.

FIGURE 3. Macropelopia multifasciata sp. nov., adult male. (A) Fore femur and tibia. (B) Mid femur and tibia. (C) Hind femur and tibia. (D) Apex of front tibia.

FIGURE 4. Macropelopia multifasciata sp. nov., pupa. (A) Thoracic horn. (B) Dc1 and Dc2. (C) Wing sheath. (D) Tergite I. (E) Abdomen.

FIGURE 5. Macropelopia multifasciata sp. nov., larva. (A) Head capsule. (B) Chaetotaxy of the head, dorsal. (C) Chaetotaxy of the head, ventral. (D) Basal multi-branched seta of procercus. (E) Posterior parapod apex.

FIGURE 6. Macropelopia multifasciata sp. nov., larva. (A) Antenna. (B) Maxillary palp. (C) Mandible. (D) Dorsomentum. (E) M appendage (F) Ligula and paraligula.