Cincticostella gosei Allen 1975

Cincticostella gosei Allen, 1975

urn:lsid:zoobank.org:act: 9190CC31-1200-4BDD-A463-6FE7D8E7411D

Ephemerella TEB Gose, 1969: 135, figs. 38–55 (nymph). Types: nymph, from Thailand. Renamed as Ephemerella (Cincticostella) gosei by Allen, 1975: 20.

Cincticostella gosei: Allen 1980: 82; Zhou et al., 1997: 222 (first record from China). Kluge, 2004: 307; Jacobus & McCafferty, 2008: 239; Xie et al., 2009: 53; Martynov et al., 2019: 148; Zheng & Zhou, 2021: 3; Martynov et al., 2021: 145 (nymph photographed, India).

Serratella thailandensis Allen, 1980: 76. Types: nymph, from Thailand. Synonymized by Edmunds & Murvosh, 1995: 157.

Ephemerella (Serratella) nigromaculata Xu et al., 1980: 5, figs. 1–7 (male). Type: male, from China (Zhejiang province); Gui, 1985: 89; You & Gui, 1995: 131, fig. 140 (male). Synonymized by Zhou, 2013: 177.

Notacanthella nigromaculata: Jacobus & McCafferty, 2008: 236.

Ephemerella (Serratella) tianmushanensis Xu et al., 1980: 5, figs. 8–14 (male). Type: male, from China (Zhejiang province); Gui, 1985: 89; You & Gui, 1995: 132, fig. 141 (male). Synonymized by Zhou, 2013: 177.

Notacanthella tianmushanensis: Jacobus & McCafferty, 2008: 236.

Nymph (in alcohol): body length 5.5–7.0 mm, caudal filaments 3.0– 4.5 mm, antennae 1.0– 1.5 mm. Body reddish brown to dark brown (Fig. 1A), whole body covered with very tiny pale hair-like setae. Head: dark brown dorsally but area around ocelli pale, forming three obvious dots; antennal length ca. 1.2X of head width, yellowish to brown, with tiny hair-like setae between segments except base; genae slightly expanded to form clear elbow; free margins of clypeus with pale cilia (Fig. 1B). Mouthparts: labrum subquadrate, leading margin with shallow emargination; submedian margin with two rows of long hair-like setae; dorsal surface of labrum with numerous hair-like setae while ventral surface with same kind of setae beside median groove only (Fig. 1C). Left mandible: basal half of outer margin with long hair-like setae; outer incisor divided into 4 denticles but inner one with 3 denticles only; prostheca strong (Fig. 1F). Right mandible: both outer and inner incisor with 3 apical denticles, with hair-like setae on outer margin and mesoapical margin as in Fig. 1E. Maxillae: hair-like setae on basal half outer margin and apical mesal half inner margin; crown with dense hair-like and spine-like setae, two dentisetae stronger than others and more conspicuous; cardo with sparse hair-like setae on outer margin; maxillary palp absent (Fig. 1G). Hypopharynx: lingua round, with tiny cilia on apex; superlinguae with almost straight outer margins, with hair-like setae on apical and inner margins (Fig. 1D). Labium: all parts with hair-like setae or cilia, those on glossae, paraglossae and labial palpi longer; glossae sub-round in shape, surrounded by sub-oval paraglossae; basal segment of labial palpi subequal to second one in length but slightly broader, with hair-like setae on outer margin; both inner and outer margins of second segment with same setae; apical segment length ca. 1/3 length of segment two, with very tiny setae on surface; apex slightly narrower than base; its length ca. 3X width (Fig. 1H). Thorax:Anterolateral angle of pronotum expanded forwards into acute projections, pronotum extended laterally into same level of anterolateral projections of mesothorax, lateral lines of pronotum almost straight and parallel. Foreleg brown except base and apex of femora; length ratio of femora: tibiae: tarsi=2.0: 1.6: 1.0; femora with row of transverse spine-like setae subapically, outer margin with spine-like and tiny hair-like setae (Fig. 2D); tibiae darker than other segments, with spines and setae on outer, inner and dorsal margins; tarsi also with setae and spines on surface, those on apical area denser (Fig. 2A). Midleg: slightly longer than foreleg, femora: tibiae: tarsi=2.4: 1.8: 1.0, femora expanded progressively from base to apex (Fig. 2E); other structures similar to foreleg (Fig. 2B). Hindleg: longer and flatter than midleg, femora: tibiae: tarsi=2.9: 2.5: 1.0, others similar to midleg (Fig. 2C). Femora of midleg and hindleg with clear longitudinal ridge in middle, posterior margins slightly serrated (Fig. 2 E-F). Claws of all legs similar in shape and structure, with several apical setae and seven denticles along inner margins but basal one much smaller (Fig. 2L). Abdomen: terga II–IX with pair of median ridges which expand into distinct tubercles on posterior margins; posterolateral angles of terga extended into small but sharp spines (Fig. 1A). Gills on terga III–V similar, subquadrate to oval, ventral lamellae with numerous leaf-like lobes further divided into two clusters (Fig. 2G–I); gill on terga VI slightly more slender than anterior gills, ventral lamellae consisting of several lobes but without bifurcation (Fig. 2J); gill on terga VII much smaller than others, completely covered by gills of previous segment, both dorsal and ventral lobe membranous with irregular shape (Fig. 2K). Caudal filaments with brown base, but progressively paler from base to apex, each articulation with rings of short spines and setae (Fig. 1A).

Male imago: body length 7.0–8.0 mm, caudal filaments 7.0–9.0 mm, forewing 7.0–8.0 mm, hindwing 1.5–2.0 mm. Body generally brown to black (Fig. 3A). Antennae brown except apex, with setae ring between segments. Upper portion of compound eyes reddish to pink while basal portion dark; distance between two eyes shorter than half width of median ocellus. Ocelli with dark base but pale apex. Prosternum dark brown, with slightly converging anteriorly longitudinal carinae, maximum width between carinae ca. 1.5X minimum width. Basisternum of mesosternum dark brown, with parallel furcasternum (Fig. 4C). Forewing: transparent except around stigma area; a long vein between C and Sc of stigma divided crossveins into two portions. Rs leaves MA at very base, MA forked at 2/3 point from base to outer margin; MP forked more basal than fork of Rs; marginal intercalaries almost meet nearby crossveins (Figs. 4A, 5A). Hindwing: costal projection small, rounded, located at 1/3 point from base to apex; MP forked between forks of R 1 +MA and MA (Figs. 4B, 5B). Legs: femora: tibiae: tarsi of foreleg=1.4: 2.2: 1.7, tarsal segments 1–5 arranged in decreasing order= 2, 3, 4, 5, 1; femora brown, tibiae dark, tarsi pale, first segment of tarsi much shorter than others (Fig. 3A). Femora: tibiae: tarsi of midleg=1.0: 0.7: 0.4, tarsal segments arranged in decreasing order=5, 1, 2, 3, 4; color pattern similar to foreleg except basal tarsi brown. Femora: tibiae: tarsi of hindleg=1.3: 1.0: 0.5, tarsal segments arranged in decreasing order=5, 1, 2, 3, 4, color pattern similar to midleg (Fig. 3A). Claws of all legs similar: one blunt and one hooked. Genitalia: styliger plate with median projected lobe. Basal segment of forceps broader than others but much shorter than second one; second segment slightly constricted at point in apical 1/3, bending inwards smoothly. Length of segment III ca. 2X width, slightly tapered from base to apex. Penes length 2/3 length of forceps, with irregular dark stripes or streaks, slightly narrowed from base to apex, with shallow median emargination (Fig. 4E–G). Caudal filaments dark in basal 1/3, other portion pale (Fig. 3A).

Female imago: body length 6.5–8.0 mm, caudal filaments 7.0–9.0 mm, forewing 7.5–9.0 mm, hindwing 1.5– 2.0 mm. Color pattern similar to male (Fig. 3B). Lengths of femur: tibia: tarsus of foreleg=1.0: 1.3: 0.7, tarsal segments arranged in decreasing order of length=5, 2, 3, 4, 1; femur: tibia: tarsus of midleg=1.1: 0.9: 0.5, tarsal segments arranged in decreasing order=5, 3, 2, 4, 1; femur: tibia: tarsus of hindleg=1.4: 1.1: 0.5, tarsal segments arranged in decreasing order=5, 3, 2, 4, 1. Sterna of segment VII extended into narrow lobe, subanal plate with depressed posterior margin (Fig. 4D).

Male subimago (Fig. 3C): body length 6.0– 7.5 mm, caudal filaments 6.0–8.0 mm, forewing 7.0– 8.5 mm, hindwing 1.4–1.8 mm. Body general brown to gray. Scutellum with long and pointed posterior prolongation. Forewings and hindwings semi-hyaline, with tiny setae on hind margins. Lengths of femur: tibia: tarsus of foreleg=0.8: 1.0: 0.9, tarsal segments arranged in decreasing order of length=3, 2, 4, 5, 1; femur: tibia: tarsus of midleg=0.9: 0.7: 0.4, tarsal segments arranged in decreasing order=5, 1, 2, 3, 4; femur: tibia: tarsus of hindleg=1.0: 0.8: 0.4, tarsal segments arranged in decreasing order=5, 1, 2, 3, 4.

Female subimago (Fig. 3D): body length 5.5–7.0 mm, caudal filaments 6.0– 7.5 mm, forewing 7.0–8.0 mm, hindwing 1.4–1.8 mm. Body general yellowish to brown. Lengths of femur: tibia: tarsus of foreleg=0.8: 0.8: 0.5, tarsal segments arranged in decreasing order of length=5, 2, 3, 1, 4; femur: tibia: tarsus of midleg=0.9: 0.7: 0.4, tarsal segments arranged in decreasing order=5, 1, 2, 3, 4; femur: tibia: tarsus of hindleg=1.2: 1.0: 0.5, tarsal segments arranged in decreasing order=5, 1, 2, 3, 4.

Egg. Scanned egg is 0.13 mm length and 0.08 mm width. Oval, with one polar cap, surface sculptured with hexagonal structures and decorated with sparse tubercle-like projections (Fig. 6).

Distribution. China (Yunnan, Guizhou, Sichuan, Anhui, Gansu, Jiangxi, Zhejiang, Jiangsu, Shaanxi, Henan provinces), Thailand, India (Fig. 7).

Ecology. The stream where the C. gosei nymphs were collected is 4.0–8.0 m wide, with water depth 0.2–0.5 m, and contains stones of various sizes (Fig. 8). The nymphs were collected under stones. The nymphs emerged at about 4:00 PM to 8:00 PM local time in April, most around 5:00 PM; before molting to subimago, the nymph were seen climbing on the substrates underwater or floating on water surface for about 30 minutes. Subimagos persisted for 24–36 hours, most of them molted around 1:00 AM to 6:00 AM. The observed lifespan of imagos was about 3 days.

Molecular similarity: The COI gene sequence of our C. gosei is most similar to Thai materials under the same species name. The distance between them is 0.170 while the average distance of known species in the genus Cincticostella is 0.217 –0.270 (Table 2).