Oropuella, Inc. & Road & Missoula & E-mail, 2020

Fasbender, Andrew, 2020, OROPUELLA, A NEW GENUS OF ORTHOCLADIINAE FROM THE WESTERN NEARCTIC Abstract, CHIRONOMUS Journal of Chironomidae Research 33, pp. 17-30 : 18-23

Oropuella new genus

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Type species: Oropuella eidolon sp. n.

Etymology: Oro- Greek for “mountain,” as the known species is recorded from mountain streams; - puella the Latin for “maiden,” in reference to the delicate appearance of the larva. The gender of the name is feminine.

Diagnostic characters: Adult male. Eye bare, with wedge shaped dorsomedial extension. Antenna with 13 flagellomeres, apical flagellomere weakly clavate with emarginate apex. Wing membrane with extensive macrotrichia at apex and along posterior margin. Anal point strongly developed, apex extending beyond inferior volsella.

Pupa. Habitus pale (alcohol preserved specimens). Thoracic horn present, broadly flattened, with numerous triangular spinules. Wing sheath with single pearl row. Abdominal tergites II–VIII with rows of prominent triangular spinules along posterior margin. Pedes spurii B present on II, large and triangular without fingerlike apex, extending over ¼ length of segment. Posterior margin of sternite VIII with sexual dimorphism: row of spinules in male, simple in female. Anal lobes with broad rounded apex, three apical macrosetae with length subequal to anal lobe.

Larva. Habitus pale, cranium very light (alcohol preserved specimens).Antennae with six segments, apical segment minute and hair-like, desclerotized break at base of second segment. SI setae plumose. Mentum pale tan, with single broad median tooth and five lateral teeth; ventromental plates double, extending well beyond setae submenti. Posterior abdominal segment not directed ventrally.

Generic description: Adult male (from pharate material): Habitus pale to brown.

Antenna. Figs 1a, b . 13 flagellomeres, groove beginning at flagellomeres 3–4. Antennal ratio (AR 0.19–0.32. Apical segment of antenna weakly clavate, apex emarginate without apical seta. Plume fully developed.

Head. Eye bare, with wedge shaped posteromedial extension. ~9 temporal setae, uniserial. With 5 palpomeres; 3 & 4 subequal, 5 slightly longer than 4.

Thorax. Antepronotum not narrowed medially, lateral setae present. Acrostichals strong, decumbent, extending from anterior of prescutum beyond midpoint of scutum; 19–24 dorsocentrals, irregularly staggered in two rows; 8 prealars, uniserial; supraalars absent; 4 scutellars, uniserial. Postnotum bare.

Wing. Setae present on all veins; membrane with macrotrichia in apical third and along posterior margin. Squama with several setae.

Legs. Sensilla chaetica absent. Tibial spurs absent, hind tibial comb present. Pseudospurs absent; tarsomere IV cylindrical, 1.3x length of V. Pulvilli weakly developed.

Abdomen. Tergites I–VII with setae in anterior and posterior rows medially, irregularly placed laterally; tergite VIII with 3 irregular rows of setae. Sternites with setae medially.

Genitalia. Fig. 2 . Anal point strongly developed, extending beyond inferior volsella, base of anal point pentagonal, rapidly tapering to straight sided stylus, 6 scattered setae at free base of stylus, apex rounded, glabrous and hyaline. Sternapodeme without oral projections. Coxapodeme curved, apex acute. Virga absent. Gonocoxite without superior volsella, inferior volsella well developed, apex rounded. Gonostylus with crista dorsalis weak or well developed; gonocoxite/gonostylus ratio approximately 2.0.

Adult female (from pharate material). Description covers characters differing from the male.

Antenna. Figs 1c–e . Five flagellomeres; AR 0.24– 0.35.

Head. Dorsomedial eye extension weak. Five temporal setae.

Thorax. Acrostichals ending just before midpoint of scutum.

Abdomen. Tergite I with a single row of setae, tergites II–VII with anterior, posterior, and uniserial lateral rows of setae.

Genitalia. Fig. 3 . Tergite IX plate-like, undivided. Gonapophysis VIII with dorsomedial lobes divided, broadly separated or nearly touching; ventrolateral lobes nearly touching or fused medially. Labia simple, membranous. Two spermathecae subequal, necks symmetrical. Tergite X weakly developed; cerci large, pendulant.

Pupa. Fig. 4 . Habitus pale.

Cephalothorax. Cephalic tubercles and frontal warts absent. Frontal setae absent. Antennal sheath smooth. Postorbitals absent. Antepronotum with one pair simple median setae. Thoracic horn long, flattened with broad apex, densely covered in strong, acute spinules. Two precorneal setae, three prealars present. Thorax smooth, wing sheath with a single pearl row, nose absent.

Abdomen. Tergite I without shagreen, tergites II– VIII with triangular shagreen, sparse anteriorly becoming denser toward posterior margin. Tergite I without spinules, tergites II–VIII with a strong band of 2–4 rows of dark spinules on posterior margin. Sternites VI–VII with similar posterior band of spinules. Conjunctives without polygonal sclerotization. Pedes spurii A absent; pedes spurii B conspicuous, triangular, length subequal to basal width. Posterior margin of sternite VIII sexually dimorphic, male with band of spinules similar to preceding sternite, female smooth. Abdominal setation (tentative, some setae obscured): tergite I with 0 D, 0 L; tergites II–VI 5 D, 1 L; tergite VII– VIII 5 D, 2 L; D 2–5 and L setae with adjacent sensillum chaetica. No taeniae. Anal lobe with rounded apex, apical spinules ventrally, without fringe, 3 subequal macrosetae apical, subequal to anal lobe length. Male genital sac subequal to anal lobes.

Larva (4 th instar). Fig. 5 . Measurements (n=5): total length 3.8–4.4 (4.1) mm; body/head length ratio 18–21 (19.5); head capsule length 191–230 (196) μm; head capsule width 144–178 (165) μm; antennal ratio 1.13–1.31(1.15). Habitus pale, head capsule light colored.

Head. Antenna with 6 flagellomeres; 6th segment hair like; 2nd segment divided near its base by a weakly sclerotized break; blade shorter than flagellum, reaching apex of 4th segment. SI plumose; SII and SIII with a few apical serrations. Pecten epipharyngis 3 short simple spines. Premandible with 4 teeth, brush absent. Mandible with 1 apical tooth and 4 inner teeth, apical tooth shorter than combined width of inner teeth, all teeth and apical portion of mandible pale tan. Mentum with simple median tooth and 5 pairs of lateral teeth, very pale tan. Ventromental plates well developed, extending beyond outer margin of mentum, and second set of smaller plates lying inside the main plate, directed perpendicular to postoccipital margin, posterior apex rounded. Ventromental plates extend well beyond setae submenti. Beard absent.

Thorax and abdomen. Body segments much longer than wide resulting in an elongate habitus. Body setae absent. Anterior parapods with serrated claws. Posterior parapods with simple claws. Procercus small, slightly wider than long, weakly sclerotized, with 4 anal setae. Anal tubules shorter than posterior parapods.

Remarks

A suite of morphological features from all life stages distinguish Oropuella . Males can be separated from similar genera (without ommatrichia, with acrostichals reaching the antepronotum, macrotrichia on the wing membrane, and simple gonostylus) by the following features: dorsomedial eye extension wedge shaped (parallel sided in Parametriocnemus ), tibial spurs absent (present in Paraphaenocladius ), tarsi without pseudospurs (present on tarsomeres 1 & 2 in Metriocnemus Wulp ), pulvilli weak (well developed in Pseudorthocladius Goetghebuer ), anal point elongate (absent in Apometriocnemus Saether , short in Pseudorthocladius ), virga absent (present in Heterotrissocladius Spärck, Parametriocnemus , and Thienemannia Kieffer ). It is challenging to separate the males of Oropuella from Paraphaenocladius , with the most reliable features being the combination of a long, parallel sided anal point and lack of a virga (not found in any of the described Paraphaenocladius ), and the absence of tibial spurs ( Saether & Wang 1995). Another potential feature to separate this genus from Paraphaenocladius is that C and R 4+5 appear to terminate distal to M 3+4 based on the pattern of vein macrotrichia in the developing wings, but it will require examination of eclosed specimens to confirm this character. Pupae are similar to Parametriocnemus , but have a less elongate pedes spurii B (length subequal to basal width). The configuration of the larval mentum (weakly convex, with double ventromental plates) is close to Parametriocnemus and Paraphaenocladius , but the pale tan mentum and desclerotized break in the second antennal flagellomere distinguish it from these taxa.

Key to the adult males of Oropuella

Gonostylus with prominent triangular crista dorsalis ( Fig. 2b ) ..................… Oropuella eidolon sp. n.

Gonostylus with weak, straight crista dorsalis ( Fig. 2e ) ................................… Oropuella pallida sp. n.

Key to the adult females of Oropuella

Tergite IX triangular ( Fig. 3d ) … Oropuella sp. F 1

Tergite IX semicircular ( Figs 3e, f ) ………..…… 2

Dorsomedial lobe of gonapophysis VIII broadly separated medially ( Fig. 3b ) ...… Oropuella sp. F 2

Dorsomedial lobe of gonapophysis VIII nearly touching medially ( Fig. 3c ) …… Oropuella sp. F 3

Key to the pupae of Oropuella

Sternite VIII with posterior spinule band ( Figs 4c, d ) (male) ………..............................................… 2

Sternite VIII without posterior spinule band ( Figs 4 e–g ) (female) …… Oropuella spp. F 1, F2 and F3

Sternite V with posterior spinule band ( Fig. 4c ) ……….........................… Oropuella eidolon sp. n.

Sternite V without posterior spinule band ( Fig. 4d ) …………......................… Oropuella pallida sp. n.

Figures

Figure 1. Adult antennae. Male antennae: a) Oropuella eidolon n. sp.; b) Oropuella pallida n. sp. Female antennae: c) Oropuella sp. F1; d) Oropuella sp. F2; e) Oropuella sp. F3. a), b) and d) exhibit some foreshortening due to the position of the antenna on the specimen; setae omitted; scale bar = 100 μm.

Figure 2. Male genitalia. a–c Oropuella eidolon n. sp.: a) anal point and gonopods; b) left gonopod in dorsal view, right gonopod in ventral view; c) sternapodeme and phallapodemes. d–f) Oropuella pallida n. sp.: d) anal point and gonopods; e) left gonopod in dorsal view, right gonopod in ventral view; f) sternapodeme and phallapodemes. Only significant setae illustrated; scale bars = 100 μm.

Figure 3. Female genitalia. a–c overall dorsal view: a) Oropuella sp. F1; b) Oropuella sp. F2; Oropuella sp. F3. d–f overall ventral view: d) Oropuella sp. F1; e) Oropuella sp. F2; f) Oropuella sp. F3. g–i spermathecae: g) Oropuella sp. F1; h) Oropuella sp. F2; i) Oropuella sp. F3. Scale bar = 100 μm.

Figure 4. Pupae. a) Oropuella eidolon n. sp. complete abdomen, dorsal view; b) Oropuella sp. F2 thoracic horn; c) Oropuella eidolon n. sp. apical abdominal segments, ventral view; d) Oropuella pallida n. sp. apical abdominal segments, ventral view; e) Oropuella sp. F1 apical abdominal segments, ventral view; f) Oropuella sp. F2 apical abdominal segments, ventral view; g) Oropuella sp. F3 apical abdominal segments, ventral view. Setae omitted except in 4a, setae D2–5 illustrated only on tergite V; scale bars = 100 μm.

Figure 5. Larval head. A) labral setae; b) premandible; c) antenna; d) mentum and ventromental plates; e) mandible. Scale bar = 25 μm.