Parafronurus youi Zhou & Braasch, 2003: 148

Zhang, Wei, Han, Na, Zhang, Min & Zhou, Chang-Fa, 2019, Redescription of Parafronurus youi and generic affinities (Ephemeroptera, Heptageniidae, Ecdyonurinae), Zootaxa 4623 (1), pp. 132-140 : 133-138

publication ID	https://doi.org/ 10.11646/zootaxa.4623.1.8
publication LSID	lsid:zoobank.org:pub:4577DBD8-82EB-4CCC-BD8E-B76E2A62C01F
DOI	https://doi.org/10.5281/zenodo.5940951
persistent identifier	https://treatment.plazi.org/id/03D087F4-622C-FFED-FF36-4B5370ECFF5E
treatment provided by	Plazi
scientific name	Parafronurus youi Zhou & Braasch, 2003: 148
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Parafronurus youi Zhou & Braasch, 2003: 148 View in CoL , figs. 1–20, adults and nymphs. Holotype: male, from Nanjing , China.

Parafronurus youi: Webb and McCafferty, 2008: 14 View in CoL ; Zhou et al., 2015: 120.

Description. Nymph (in alcohol, Figs 1 View FIGURE 1 –5): body length 12.0–14.0 mm, caudal filaments 14.0–15.0 mm, head width 3.5 mm, antennae 2.0 mm, smooth; head capsule oblong, anterior and posterolateral margins slightly convex, posterior margins straight; anterior margin slightly thickened ( Fig. 1 View FIGURE 1 A–B).

Mouthparts: labrum width 1.5 mm, with shallow median emargination and ventral groove, dense setae on free margins, dorsal and ventral surfaces, those on dorsal surface longer and denser; an additional row of short bristles on ventral anterior margin, those near ventral groove stronger ( Figs 2 View FIGURE 2 A–B, 3A); both left and right mandibles with long dense setae on outer margin, tuft of spine-like setae on inner apex, prostheca with 7–10 fimbriate bristles ( Figs 2 View FIGURE 2 C–D, 2L, 3D–E); outer incisor of left mandible with serrated margins and one larger terminal denticle, row of spines on dorsal margin ( Fig. 2I View FIGURE 2 ); inner incisor with row of setae on dorsal margin, apex divided into 3 terminal denticles ( Fig. 2J View FIGURE 2 ); outer incisor of right mandible with 3 apical terminal denticles, margins serrated and dorsal margin with row of setae ( Fig. 2K View FIGURE 2 ); inner incisor divided into 2 denticles and each denticle with 2 sharp spines ( Fig. 2L View FIGURE 2 ); maxillae with scattered fimbriate setae on ventral surface (Fig. 5B), distal dentiseta and proximal dentiseta simple (Fig. 5A); row of 14–20 comb-shaped setae on crown of galea-lacinia, dense bristles and setae on mesal margin ( Figs 2 View FIGURE 2 G–H, 3F); outer margin and basal half of inner margin of first segment of maxillary palpi with setae; second segment obviously longer than basal one, outer margin with longer setae, apex with setaceous brush ( Figs 2G View FIGURE 2 , 3F View FIGURE 3 ); labium: glossae slightly expanded with narrow base, inner margin with tuft of long setae, free margin with golden spine-like setae ( Figs 2E View FIGURE 2 , 3C View FIGURE 3 ); paraglossae expanded greatly into palpable lobes, with dense short setae on surface; labial palpi broad, 2-segmented; ventral surface and free margin with setae brushes; dorsal surface with scattered short setae ( Figs 2E View FIGURE 2 , 3C View FIGURE 3 ); hypopharynx: apex of superlinguae extended into round lobe-like structure, with strong curved outer margin; lingua with setae on surface ( Figs 2F View FIGURE 2 , 3B View FIGURE 3 ).

Thorax: pronotum extended laterally ( Fig. 1 View FIGURE 1 A–B); supracoxal spurs small and round; legs yellowish brown with irregular pale margins and dots on femora; femora of all legs dorsally with 4 yellowish-brown markings, middle two dots V shaped and apical one dark brown (Fig. 4A–C). Femora of forelegs with a row of long setae on outer margin, dorsal surface with scattered spatulate setae, inner margin with short bristles; foretibiae subequal in length to femora, with row of fine setae on dorsal margins and row of tiny bristles on inner margins; foretarsi onehalf length of tibiae, with row of setae on outer and inner margins, those on apex denser and more numerous; femora of midlegs similar to fore femora, tibiae 0.9x of femora, tarsi approximate 1/3 of tibiae; tibiae with rows of tiny setae on dorsal and outer margins and one row of bristles on inner margins; tarsi of midlegs similar to foretarsi (Fig. 4B); hindlegs similar to midlegs in structure except tibiae 0.72x of femora and tibiae with additional bristles on dorsal ridge (Fig. 4C–D), tarsi of hindlegs similar to foretarsi and midtarsi; mid- and hindlegs with patellar-tibial sutures; femora of all legs with a blunt apical projection (Fig. 4A–C, 4F); claws of all legs similar, with a large basal denticle and 3 subapical denticles (Fig. 4E).

Abdomen: terga I–II pale; terga III–IX each with two pairs of pale dots, the median pair larger, especially those on terga VIII–IX, making them paler than others terga, tergum X greenish brown ( Fig. 1A View FIGURE 1 ); sterna pale but sternum VII with dark central ganglion, posterolateral angles of terga I–X extended slightly into small acute projections, larger progressively from anterior to posterior ( Fig. 1C View FIGURE 1 ); each tergum with row of pointed spines on posterior margins (Fig. 4G). Gills I banana-shaped, outer margin expanded, lamellae longer than fibrilliform portion (Fig. 4H); gills II–VI similar to each other, lamellae broad, shorter than fibrillae (Fig. 4I); gills VII with lamellae only, leaf-like and slightly asymmetrical (Fig. 4J). Terminal filament subequal to cerci, with spines and setae on articulations; cerci with whorls of spines and mesal setae on articulations ( Fig. 1 View FIGURE 1 D–F).

Male imago (in alcohol, Figs 6–8): body length 10.0–13.0 mm, cerci 25.0–28.0 mm. Compound eyes contiguous, upper portion slightly gray and lower portion black. Body brown, with dark dots and stripes.

Thorax: forecoxae relatively widely separated, making prosternum between them large and flat; mesothoracic furcasternum parallel but widely separated (Fig. 6C); mesonotum with apparent transverse suture, lateral parapsidal sutures relatively straight, jointing posterior transverse suture (Fig. 6D). Femora: tibiae: tarsi of foreleg=3.0: 3.2: 5.1, tarsal segments from basal to apical=0.8: 1.5: 1.2: 1.1: 0.5; femora with median dark dots, articulations dark; femora: tibiae: tarsi of midleg=2.5: 2.0: 1.5, tarsal segments arranging in decreasing order as 5, 1, 2, 3, 4; femora: tibiae: tarsi of hindleg=3.0: 2.2: 1.0, tarsal segments arranging in decreasing order as 5, 1, 2, 3, 4. Forewings transparent, veins and crossveins pigmented reddish brown while crossveins at wingbase, costal, subcostal and stigmatic area darker; several crossveins in stigmatic area of costal section divided; Rs and MP forked equidistant from base of wing to margin; MA forked over 1/2 of distance from base of wing to margin; Rs, MA and MP forked symmetrically (Figs 7A, 8A); hindwings with clear basal costal projections, MA forked distally but MP forked basal (Figs 7B, 8B); length of hindwings 0.32x forewings (Figs 7A–B, 8A–B).

Abdomen: each tergum of abdomen I–VII with a pair of oblique dark brown stripes and a pair of dorsal markings; posterior margin of abdominal terga I–VII with thin brown markings, terga VII–IX paler (Fig. 7F). Cerci pale (basal segments slightly reddish), every two articulations dark brown while several basal ones deep colored too.

Genitalia: styliger plate with median convex posterior margin and 2 lateral lobes; combined length of forceps segments 3–4 less than half segment 2, segment 4 2/ 3x segment 3; penes fused in basal half, apical half separated but contiguous; stem of penis base sclerotized laterally (Fig. 7C–D); with median spine-like titillators, subapically and mesally (Fig. 7D).

Male subimago (in alcohol): body 10.0–12.0 mm, forewing 10.0–12.0 mm, hindwing 3.0–4.0 mm, cerci 16.0– 17.0 mm; color pattern similar to male. Femora: tibiae: tarsi of foreleg=3.0: 2.0: 2.2, tarsal segments arranging in decreasing order as 1, 2, 3, 4, 5; those of midleg=2.5: 2.0: 1.2, length order of tarsal segments in decreasing as 1, 5, 2, 3, 4; those of hindleg=3.0: 2.5: 1.0, tarsal segments similar to midlegs. Wings semi-transparent, yellowish brown but crossveins clear; articulations of cerci brown to dark.

Female imago (in alcohol, Figs 6B, 7E): body length 10.0–12.0 mm, forewing 10.0–12.0 mm, hindwing 3.0– 4.0 mm, cerci 25.0–29.0 mm. Body brown with dark dots and stripes. Femora: tibiae: tarsi of foreleg=2.5: 2.5: 2.0, tarsal segments arranging in decreasing order as 2, 1, 3, 5, 4; those of midleg=2.8: 2.2: 1.0, length order of tarsal segments in decreasing as 5, 1, 2, 3, 4; those of hindleg=3.0: 2.5: 1.0, tarsal segments similar to midlegs (Fig. 6B). Wings transparent, more pigmented than in male imago. Subgenital plate almost reaching posterior margin of sternum VIII; subanal plate with convex posterior margin (Fig. 7E). Articulations of cerci brown to dark.

Female subimago (in alcohol): body 10.0–13.0 mm, forewing 10.0–12.0 mm, hindwing 3.0–4.0 mm, cerci 17.0–18.0 mm. Body dull, wings yellowish brown, cerci with dark articulations and tiny setae. Color pattern similar to female imago. Femora: tibiae: tarsi of foreleg=3.0: 2.8: 1.5, tarsal segments arranging in decreasing order as 2, 1, 3, 5, 4; those of midleg=3.2: 2.8: 1.5, length order of tarsal segments in decreasing as 5, 1, 2, 3, 4; those of hindleg=3.5: 3.0: 1.0, tarsal segments similar to midlegs.

EGG ( Fig. 9 View FIGURE 9 ): Egg oval ( Fig. 9A View FIGURE 9 ), decorated with tubercle-like projections ( Fig. 9B View FIGURE 9 ). Egg surface with irregular small knob-terminated coiled threads (KCTs).

Diagnosis. In the original paper of Zhou & Braasch (2003), the following characters are not described accurately: (1) Shape of nymphal gill VII (more slender); (2) Prostheca (with only 8–9 simple bristles); (3) Scattered setae on ventral surface of maxillae (tiny setae); (4) Prosternum and mesosternum (characters not mentioned); (5) Shape and venations of wings. In this paper, with the help of digital and SEM photos, those characters are presented clearly.

According to system provided by Webb & McCafferty (2008), the genus Parafronurus should be placed into subfamily Ecdyonurinae because of following characters: nymphal banana-shaped gills I, scattered setae on ventral surface of maxillae, serrated margins of mandibular incisors, imaginal medial depression of mesothoracic furcasternum with parallel margins.

Based on the structures described in this paper and information provided by Zhou & Braasch (2003) and Webb & McCafferty (2008), the following combined characters can differentiate the genus Parafronurus from other Ecdyonurinae . In nymph: (1) anterior margin of head capsule slightly thickened, without any emargination, notch, spine or setae; (2) labrum about 0.43x head width, with shallow median notch and dense setae; (3) outer margins of mandibles with dense long setae, incisors divided apically; (4) distal and proximal dentisetae simple; (5) glossae of labium slightly expanded, with short bristles on free margins; (6) paraglossae of labium expanded greatly; (7) superlinguae of hypopharynx with greatly waved outer margin and round apex; (8) pronotum expanded laterally into small lobes; (9) supracoxal spurs round; (10) abdominal terga without spine, ridge or large elongated posterolateral projections; (11) lamellae of first gills banana-shaped; (12) articulations of terminal filament with rings of spines and setae, cerci with spines on articulations too, but only interfacing side with setae. In male imago: (13) compound eyes contiguous; (14) relatively large flat portion between forecoxae of prosternum; (15) crossveins of forewings distinctly pigmented; (16) some crossveins at stigmatic area divided further; (17) legs (foretarsi longer than tibiae, hindtarsi about half tibiae); (18) shape of genitalia and forceps; (19) penes without spines; (20) convex posterior margin of sternum IX of female imago.

Among those characters, the shape of head capsule, relatively wider labrum and its setae pattern, labium (glossae with strong bristles on margins), gills (shape of gills I and VII), imaginal wings (some crossveins divided in stigmatic area), genitalia (forceps and penes), patterns of maxillae and swimming setae on caudal filaments are unique to the genus, especially simple proximal and distal dentisetae, and ring of swimming setae on terminal filament and mesal setae on cerci articulations.

Affinity. Clearly, the genus Parafronurus belongs to the subfamily Ecdyonurinae ( Webb & McCafferty 2008) or Ecdyonurus /fg1 ( Kluge 2004). Because of the presence of fimbriate setae on the ventral surface of maxillae, it is close to such genera as Compsoneuria Eaton, 1881 , Compsoneuriella Ulmer, 1939 , Ecdyogymnurus Kluge, 2004 , Ecdyonurus Eaton, 1868 , Leucrocuta Flowers, 1980 , Nixe Flowers, 1980 ( Webb & McCafferty 2008; Sartori 2014a). On the other hand, the presence of simple distal dentisetae on maxillae and primarily swimming setae on cerci and terminal filament seems to indicate this genus is related to Paracinygmula Bajkova, 1975 , Nixe Flowers, 1980 and Rhithrogeniella Ulmer, 1939 ( Kluge 2004, Sartori 2014b). Considering the Oriental distribution of the latter, it is believed that Parafronurus may be closer to Rhithrogeniella . Certainly, its exact relationship within the different genera in Ecdyonurinae needs more research.