Potamanthodes nanchangi Hsu, 1936

Li, Wen-Juan, Mu, Peng-Xu & Zhou, Chang-Fa, 2022, Systematics of Potamanthodes nanchangi Hsu, 1936 (Ephemeroptera: Potamanthidae), Zootaxa 5213 (2), pp. 149-158 : 151-157

publication ID	https://doi.org/ 10.11646/zootaxa.5213.2.3
publication LSID	lsid:zoobank.org:pub:6ADDF394-E8DE-43E0-83DA-E656D5DAA6BB
DOI	https://doi.org/10.5281/zenodo.7362084
persistent identifier	https://treatment.plazi.org/id/1F5B0B21-FFA2-784B-FF71-9881FF0B6A06
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scientific name	Potamanthodes nanchangi Hsu, 1936
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Potamanthodes nanchangi Hsu, 1936: 322 . Types: male, Fig. 5 View FIGURE 5 , from Jiangxi province, China.

Neopotamanthodes nanchangi: Hsu 1937: 223 , Fig. 46; Gui 1985: 91; You & Gui 1995: 127, Fig. 136.

Potamanthus nanchangi: Bae & McCafferty 1991: 70 View in CoL (subgenus incertae sedis); Zhou 2013: 203; Zhou et al. 2015: 253.

Potamanthodes nanchangi: Kluge 2004: 223 .

Mature nymph (in alcohol): body length 9.8–11.5mm, caudal filaments 6.0– 7.5mm. body pale to yellowish but with reddish brown to dark brown stripes and dots ( Fig. 1A View FIGURE 1 ).

Head: Pale, a rough pair of brown stripes on clypeus to occiput, 3–5 transverse stripes linking them together; four additional brown dots on occiput, shortest distance between two eyes: diameter of one eye = 3.0–4.0 ( Figs 1A View FIGURE 1 , 2A View FIGURE 2 , five nymphs measured). Mouthparts: labrum nearly oval but with a shallow median groove on anterior margin; both dorsal and ventral surfaces with hair-like setae, those on dorsal surface and free margins relatively longer but sparser, ventral setae denser but shorter than dorsal ones; an additional setae row along anterior groove ( Fig. 3A View FIGURE 3 ). Superlinguae of hypopharynx with hair-like setae on free margins; lingua with a V-shaped median groove which further with very fine hair-like setae along margins ( Fig. 3B View FIGURE 3 ). Both mandibles with distinct tusks which visible in dorsal view ( Figs 1A View FIGURE 1 , 2A View FIGURE 2 ); spines and hair-like setae on outer margin; apexes of outer and inner incisors of left mandible divided into three teeth, prostheca with a denticle and a tuft of tine spines ( Fig. 3C View FIGURE 3 ). Apexes of outer incisor of right mandible with three teeth but inner one with two only; prostheca represents as a serrated denticle; first denticle of molar near prostheca expanded and clear, a tuft of hair-like setae on inner corner under molar ( Fig. 3D View FIGURE 3 ). Inner and outer margins of maxillae with hair-like setae, distal dentisetae and proximal dentisetae longer and broader than others ( Fig. 3E View FIGURE 3 ); a tuft of spines on apex; outer margin of basal segment of maxillary palpi with hair-like setae too, surfaces of second and third segments of maxillary palpi with relatively longer hair-like setae. Length ratio of three segment = 1.0: 0.7: 1.2; cardo also with hair-like setae ( Fig. 3F View FIGURE 3 ). Labium: glossae and paraglossae with dense hairlike setae on both ventral and dorsal surface; glossae near oval, paraglossae rough heart-shaped; the latter width ca. 4 times of glossae; basal segment of labial palpi broader than second one, the latter slightly broader than apical one; length ratio of them from base to apex = 1.0: 0.7: 0.7. Hair-like setae on outer margins of basal and second segments of labial palpi but whole surface of apical segment with hair-like setae and spines, especially on apex and inner margins; mentum and submentum with sparse hair-like setae on ventral surface ( Fig. 3G View FIGURE 3 ).

Thorax: Color pattern as in figure 2B, a pair of dark dots near wingpad bases; pronotum expanded laterally into clear lobes; anterior portion connecting head thickened into a half-ring like structure ( Figs 1A View FIGURE 1 , 2A–B View FIGURE 2 ). Femora of all legs with three brown bands dorsally, median one larger than others and extend to ventral surface. Tibiae of all legs with wide brown band in middle and a narrow one at base, tarsi with broad median band too ( Figs 1A View FIGURE 1 , 2E–G View FIGURE 2 ). Claws of all legs similar, with smoothly curved dark apex ( Fig. 2I View FIGURE 2 ). Femora of forelegs with clear setae row in middle ( Fig. 2E, 2J View FIGURE 2 ), additional sparse hair-like setae and spatulate setae on dorsal surface, both margins also with hair-like setae( Fig. 2E View FIGURE 2 ). Whole surface of tibiae with hair-like setae but ventral ones sparser and shorter than dorsal ones; some spines and setae tuft near apex ( Fig. 2K View FIGURE 2 ). Tarsi similar to tibiae in setaceous pattern but with more setae tufts near apex ( Fig. 2E View FIGURE 2 ). Length ratio of femora: tibiae: tarsi of foreleg=1.0: 0.9: 0.6 ( Fig. 2E View FIGURE 2 ). Midlegs and hindlegs similar to forelegs except hindlegs with fine setae tuft on ventral surface near apex ( Fig. 2E–H View FIGURE 2 ). Length ratio of femora: tibiae: tarsi of midlegs = 1.0: 0.6: 0.4 ( Fig. 2F View FIGURE 2 ), that ratio of hindlegs=1.0: 0.5: 0.4 ( Fig. 2G–H View FIGURE 2 ).

Abdomen: Lateral margins of terga I–X gray to brown; terga I–IX each with 3 pairs of brown longitudinal stripes, median pair of them sometimes widened and with transverse line attaching two neighbor stripes; terga X with one big brown dot and a transverse line in the middle ( Fig. 1A View FIGURE 1 ). Gill I with sharp apex, hair-like setae on surface; length ratio of basal segment: apical segment = 1.0: 1.2 ( Fig. 2C View FIGURE 2 ). Gills II–VII similar in structure, Gill II and VII slightly shorter than others ( Figs 1A View FIGURE 1 , 2D View FIGURE 2 ). Caudal filaments with fine hair-like setae on articulations, basal half of all filaments with long hair-like setae on both margins (swimming setae) ( Figs 1A View FIGURE 1 , 2L–M View FIGURE 2 ).

Male imago (in alcohol): Body length 9.5–12.5 mm, caudal filaments 20.5–27.0 mm; body pale with reddish brown stripes and dots ( Fig. 1B View FIGURE 1 ). Head: antennae with brown scape and basal flagella, basal half of ocelli dark, a pair of dark dots between ocelli, a median reddish-brown line on occiput ( Fig. 4A View FIGURE 4 ). Compound eyes with dark basal half and gray upper half, shortest distance between them: one eye diameter = 1.6 ( Fig. 4A View FIGURE 4 , five males measured). Thorax: Median longitudinal line of thorax reddish brown. Length ratio of forefemora: tibiae: tarsi = 1.0: 1.2: 0.9, ratio of foretarsal segments I: II: III: IV: V = 0.1: 0.5: 0.3: 0.2: 0.2; length ratio of midfemora: tibiae: tarsi = 1.0: 1.2: 0.5, ratio of midtarsal segments I: II: III: IV = 0.3: 0.2: 0.1: 0.2; length ratio of hindfemora: tibiae: tarsi = 1.0: 0.9: 0.4, ratio of hindtarsal segments I: II: III: IV = 0.2: 0.1: 0.1: 0.3 ( Fig. 1B View FIGURE 1 ). Forewings yellowish but with remarkable reddish paints and dots, especially near anterior martins; crossveins also pigmented; MP 2 fused with CuA at base ( Fig. 4C View FIGURE 4 ). Hindwings pale with acute costal projection and convex curved Sc towards C; base of R 1 greatly curved towards Sc and connecting it with two crossveins; MA single, MP orienting towards CuA at base and forked asymmetrically ( Fig. 4D View FIGURE 4 ). Abdomen pale. Genitalia: length of basal segment of forceps ca. 3X combined length of second and third segment, the latter with concave apex, its length ca. 1.7X second one; inner margins of forceps with tiny projections ( Fig. 4E–G View FIGURE 4 ). Penes half-length of forceps; apical 2/3 divided, basal 1/3 fused together; ca. half penes extend out of subgenital plate ( Fig. 4F–G View FIGURE 4 ); apex of penes tapered into thin and acute tips, like needle or spine; spermatic duct in penis clear (usually darker than other place, Fig. 4E–G View FIGURE 4 ). Terminal filament shorter than cerci, all of them pale but with pigmented articulations, especially apical half ( Fig. 1B View FIGURE 1 ).

Female imago (in alcohol): Body length 10.0– 13.5 mm, caudal filaments 10.5–14.0 mm, color pattern similar to male. Head: shape and color are very similar to the male, size of compound eyes approximately equal to male, shortest distance between two eyes: diameter of one eye = 1.7 ( Fig. 4B View FIGURE 4 , five females measured). Thorax: length ratio of forefemora: tibiae: tarsi = 1.0: 1.1: 0.6, ratio of foretarsal segments I: II: III: IV: V = 0.1: 0.5: 0.3: 0.2: 0.4; length ratio of midfemora: tibiae: tarsi = 1.0: 1.1: 0.4, ratio of midtarsal segments I: II: III: IV = 0.2: 0.1: 0.1: 0.3; length ratio of hindfemora: tibiae: tarsi = 1.0: 0.9: 0.4, ratio of hindtarsal segments I: II: III: IV = 0.2: 0.2: 0.1: 0.3. Posterior margin of sternum VII slightly extended backward and thickened, produced to half-length of sternum VIII ( Fig. 4H–I View FIGURE 4 ). Posterior margin of subanal plate with semi-oval median cleft ( Fig. 4I View FIGURE 4 ).

Egg: Olive, with two polar caps, length ca. 190 μm (including polar cap), width at equator ca. 80 μm ( Fig. 5A View FIGURE 5 ); chorionic surface with some knob-terminated coiled threads (KCTs) and a distinct micropyle at equator with a diameter of about 10 μm ( Fig. 5B View FIGURE 5 ).

Habitat: The nymphs of this study were collected from median to large rivers (10–30 m width). The collecting sites usually have stony bottoms with sandy sediments. The size of stone there ranges from 10 cm to 1 m ( Fig. 6 View FIGURE 6 ).

Distribution: China (Jiangxi, Zhejiang and Hubei Province) ( Fig. 7 View FIGURE 7 ).

Diagnosis: Li & Zhou (2022) regarded the taxa Potamanthus , Potamanthodes and Stygifloris Bae et al., 1990 as genera of the family Potamanthidae , along with the two other genera ( Rhoenanthus Eaton, 1881 and Anthopotamus McCafferty & Bae, 1990 ). The males of P. nanchangi have slender and deeply divided penes ( Fig. 4E–G View FIGURE 4 , in contrast to the genera Potamanthus and Stygifloris ), MP fused to CuA at base ( Fig. 4C View FIGURE 4 , in contrast to Stygifloris and Rhoenanthus ), heavily pigmented forewings ( Fig. 4C View FIGURE 4 , in contrast to Potamanthus and Stygifloris ), hindwings with single MA but forked MP and greatly bent R 1 ( Fig. 4D View FIGURE 4 , in contrast to the genera Potamanthus , Stygifloris and Rhoenanthus ), smaller compound eyes ( Fig. 4A View FIGURE 4 , in contrast to all other genera). In nymphs, this species has shorter mandibular tusks ( Figs 1A View FIGURE 1 , 2A View FIGURE 2 , in contrast to Rhoenanthus or Anthopotamus ) and setae row on forefemora ( Figs 1A View FIGURE 1 , 2E, 2J View FIGURE 2 , in contrast to Potamanthus ), labial palpi without expanded apical segments ( Fig. 3G View FIGURE 3 , in contrast to Stygifloris ). Those aggregate characters show this species is a Potamanthodes member.

At the species level, the P. nanchangi has several unique characters. In male, its bent R 1 of hindwing almost attaching Sc ( Fig. 4D View FIGURE 4 ), its penial tips are longest in the genus, its subgenital plate with a median V-shaped cleft ( Fig. 4G View FIGURE 4 ), the male eyes are subequal to female eyes ( Fig. 4A–B View FIGURE 4 ). In nymph, its mandibular tusks can be seen clearly in dorsal view ( Figs 1A View FIGURE 1 , 2A View FIGURE 2 ), foretibiae are longer than forefemora ( Fig. 2E View FIGURE 2 ), and the setae in forefemora row are somewhat uniform in length ( Fig. 2J View FIGURE 2 ).

Its subgenital plate is similar to that of P. yunnanensis You et al., 1982 (imago known only) but their penes are totally different, the latter has no clear penial tips. The penial length of P. nanchangi is shorter than that of P. macrophthalmus You, 1984 and P. formosus Eaton, 1892 but is longer than P. yunnanensis and P. kwangsiensis Hus, 1937 . Additionally, all other known males of Potamanthodes have shallow concave subgenital plate instead of median cleft.

The eggs of P. nanchangi are similar to other species in general shape and structure (with two polar caps and two rows of KCTs). Its micropyle locates nearby a row of KCTs. In contrast, P. yooni Bae & McCafferty, 1991 and P. macrophthalmus has a near equatorial micropyle (see Bae & McCafferty 1991 and Li & Zhou 2022) while the KCTs of P. formosus eggs are somewhat randomly distributed (see Koss & Edmunds 1974). The eggs of this species are drum-shaped, much shorter than that of P. idiocerus Bae & McCafferty, 1991 (see Kang & Yang 1994).

Phylogeny: In our view, generally in the genus Potamanthodes , the evolutionary trends include smaller eyes, less pigmented spots on wings, bent Sc and R 1, shorter penes and longer penial tips in males, larger mandibular tusks, longer forelegs, longer foretibiae and its hair-like setae along inner margins, longer setae row on forefemora in nymphs (see Li & Zhou 2022). According to this standpoint, the P. nanchangi might be more apomorphic than P. yooni , P. macrophthalmus and P. formosus but more plesiomorphic than P. yunnanensis and P. sangangensis You, 1984 .