Epeorus (Proepeorus) gibbus, Ma & Lei & Li & Zhou, 2021

Ma, Zhen-Xing, Lei, Zhi-Ming, Li, Wen-Juan & Zhou, Chang-Fa, 2021, A revision of Epeorus (Proepeorus) in China, with descriptions of two new species (Ephemeroptera, Heptageniidae), Journal of Natural History 55 (17 - 18), pp. 1131-1159 : 1138-1141

publication ID	https://doi.org/ 10.1080/00222933.2021.1936679
persistent identifier	https://treatment.plazi.org/id/650487C7-FF9E-FF81-FE6F-FC32FE91FDF3
treatment provided by	Plazi
scientific name	Epeorus (Proepeorus) gibbus
status	sp. nov.

Treatment

Epeorus (Proepeorus) gibbus sp. nov. Zhou

Figs 2–4 View Figure 2 View Figure 3 View Figure 4 , 10A–B, E–F View Figure 10 , 11A–D View Figure 11 , 12A View Figure 12 , 13A–B View Figure 13 , 14A–B View Figure 14 , 15G View Figure 15 , 16F View Figure 16

Materials examined

Holotype. male imago, Chanyuan Temple (30°19′16.7″N, 119°26′55.7″E), west Tianmu Mountain , Zhejiang Province, collected by He-Ying WANG, Xiao-Li YING, 5-IV-2019 GoogleMaps . Paratypes: 2 female imagoes, 10 nymphs, same as the holotype; 2 male imago, unnamed creek in front of Tian-Mu Hotel, West Tianmu Mountain, Zhejiang Province, collected by Juan-Yan LUO, Wei ZHANG, Zhen-Xing MA, Ming ZHANG, 15-IV-2017; 1 male, 10 nymphs, Three Mile Pavilion, West Tianmu Mountain, Zhejiang Province, collected by He-Ying WANG, Xiao-Li YING, 8-IV-2019; 20 nymphs, One Mile Pavilion, West Tianmu Mountain, Zhejiang Province, collected by Yin-Fang WANG, Zhen-Xing MA, 6-IV-2019.

Nymph (in ethanol). Body length 10.5–14.0 mm (female), 9.5–10.0 mm (male), caudal filaments 11.5 mm. The body is generally yellowish brown ( Figure 2 View Figure 2 (a)).

Head. ellipsoid, head width/length ratio 1.32–1.35, anterior margin evenly convex with a row of dense setae directed anteriorly, posterolateral margin slightly narrowed (indistinct in male), posterior margin slightly convex to nearly straight. Colouration of head yellowish brown, with a pair of indistinct pale spots near anterior margin, area near anterolateral margin obviously paler ( Figures 2 View Figure 2 (c) and 4(a)); posterior margin with two tufts of setae. Labrum: anterior and lateral margins evenly convex and with a median emargination, ventral surface with long lateral bristles and brush of median fine setae; dorsal surface with four bristles antero-medially; each side with one long bristle medially, two bristles near anterolateral margin and scattered setae in different size ( Figures 3 View Figure 3 (a) and 4(b)). Mandibles: outer incisor with 2 (left mandible) or 3 (right mandible) apical teeth and serrated margins, inner incisor of right mandible with 2 apical teeth; left inner incisor slender and nearly straight, with 3 apical rounded teeth; both inner incisors with serrated outer margins. Prostheca represented by a tuft of plumose setae ( Figure 3 View Figure 3 (b,c) and 4(c,d)). Maxillae: with 4 fimbriated setae at base of apex ( Figure 15 View Figure 15 (g)); basal segment of maxillary palp with a row of bristles along distal half of outer margin, apical segment 1.3× length of basal segment ( Figure 3 View Figure 3 (e)). Hypopharynx: lingua with 2 anterolateral lobes, both lingua and superlinguae with fine dense setae anteriorly ( Figure 3 View Figure 3 (d)). Labium: with narrow separation between glossae; dorsum of glossa with a row of longitudinal dense setae, base of outer margin with a tuft of bristles, inner margin with a row of spine-like bristles ( Figures 3 View Figure 3 (f) and 4(e)); apical segment of labial palpi slightly shorter than basal segment, apical/basal segment length ratio 0.80 ( Figure 3 View Figure 3 (f)).

Thorax. Yellowish brown with irregular markings. Femora pale, with a median dark spot and irregular brown markings, outer margin of femora with a row of long setae and sparse short setae ( Figure 2 View Figure 2 (f)), dorsal surface of femora with scattered spatulate and arrow-like setae ( Figure 4 View Figure 4 (f)). Tibiae with an indistinct median brown band, tarsi brown, with darker base and apex, dorsal margins of tibiae and tarsi with a row of dense setae ( Figure 2 View Figure 2 (f)). Forefemora/foretibiae length ratio 1.0, midfemora/midtibiae length ratio 1.1, hind femora/hind tibiae length ratio 1.2. Claw with 4 subapical denticles ( Figure 4 View Figure 4 (g)).

Abdomen. Brown with dark brown markings. Each tergum of segments II–IX with a pair of submedian brown spots (among them, spots on terga V – VI more distinct) and a longitudinal median ridge (look like a median pale stripe) ( Figures 2 View Figure 2 (a,d) and 4(h)). Posterior margins of terga with dense round pointed denticles in different size ( Figure 4 View Figure 4 (i)). Sterna colourless (mature nymph with same colouration as imago). Gill I slightly expanded beneath abdomen, with a row of setae along anterior margin, distal half of anterior margin with ventral setose pads ( Figure 4 View Figure 4 (j)). Gills II– VI similar in shape, with sclerotised costal and anal margin and well developed ventral setose pads ( Figure 4 View Figure 4 (k)). Gill VII narrowed both basally and distally, slightly curved ( Figures 2 View Figure 2 (e) and 4(l)). Cerci yellowish brown, basal segments with row of dorsal setae.

Male imago (in ethanol). Body length 10.0–11.0 mm, forewing 10.0– 11.5 mm, hindwing 4.0– 4.5 mm, cerci 25.0–31.0 mm. Body pale brown with brownish black markings ( Figure 10 View Figure 10 (a)).

Head. Face fold colourless. Median area light brown, antennae brown. Ocelli basally dark, apically whitish. Compound eyes pale to grey (dark brown when alive), with darker basal half; distance between compound eyes less than width of median ocellus ( Figure 10 View Figure 10 (e)). Thorax. Dark brown. Prosternum dark brown in anterior half, brown in posterior half ( Figure 10 View Figure 10 (e)). Median depression of mesothoracic furcasternum convergent anteriorly ( Figure 10 View Figure 10 (f)). Wings transparent but with semi-hyaline stigma region. Forewings with brown veins, basally paler, costal brace dark brown; stigma region with 13–14 cross veins between C and Sc; MA forked 2/3 of distance from base to margin, MP forked 1/4 of distance from base to margin; hindwings transparent, MP forked 1/3 of distance from base to margin ( Figure 10 View Figure 10 (b)).

Legs. Forelegs dark brown, basal half of femora paler than other parts, ratios of femora: tibiae: tarsi = 2.8: 3.6: 5.7, order of tarsal segments arranged in descending order: 1, 2, 3, 4, 5. Middle and hind legs pale brown, femora of all legs with a median brown macula. Ratio of femora: tibiae: tarsi in middle legs = 2.5: 2.3: 1.1, order of tarsal segments arranged in descending length 1, 5, 2, 3, 4. Ratio of femora: tibiae: tarsi in hind legs = 2.6: 2.2: 1.0, order of tarsal segments arranged in descending length 5, 1, 2, 3, 4. Claws on each leg dissimilar, one blunt and one hooked.

Abdomen. Pale to light brown. Terga II–IX with similar markings: anterior margin with a brown transverse band; median brown band with a slender longitudinal pale line inside it; posterior margin with a dark brown transverse band ( Figure 11 View Figure 11 (a)). Tergum X with a median brown band bordering posterior margin. Colouration pattern of sterna II–VIII similar ( Figure 11 View Figure 11 (b)): 1) a reddish-brown median broad band; 2) a pair of oblique stripes located by sides of anterior of median band (medio-anterior myo-sigilla, indistinct in some individuals and segments); 3) a pair of round blanks inside the median band (medioposterior myo-sigilla). Sternum IX with a median brown band; styliger light brown, with straight posterior margin. Forceps segments I–II light brown, segments III–IV pale, combined length of segments III–IV obviously longer than half of segment II. Penis lobes divergent in apical half, expanded laterally forming a lateral hooked apex, each penis lobe with a medio-apical emargination. Median titillators small but distinct ( Figures 12 View Figure 12 (a) and, 13(a,b)). Cerci dark brown basally and paler distally, with dark annulations.

Female imago (in ethanol). Body length 10.0 mm, forewing 10.0 mm, hindwing 4.0 mm, cerci 23.0 mm. Body brownish, colouration pattern similar to male imago but paler ( Figure 11 View Figure 11 (c,d)). Thorax light brown, wings as in male. Legs with similar colouration to male, length ratios of femora: tibiae: tarsi of middle legs = 2.6: 2.4: 1.1; length ratios of femora: tibiae: tarsi of hind legs = 2.6: 2.3: 1.1 (fore legs missing). Colouration pattern of abdomen as in male, median brown band indistinct on abdominal terga VI –IX in some individuals ( Figure 11 View Figure 11 (c)). Posterior margin of subgenital plate rounded, sternum IX deeply emarginated divided into two round pointed apexes ( Figure 14 View Figure 14 (a,b)).

Etymology

The epithet gibbus is from Latin, means bulging or protuberant, referring to its unique medial ridge on abdominal terga of nymph.

Biology

Nymphs inhabits in the small-sized mountain streams (0.5–5.0 m wide, 0.1–0.5 m deep, recorded from ca. 300–700 m a.s.l.), and they are found underneath stones in moderately to fast flowing sections with rocky and stony substrate. The emergence of subimagoes was observed in the morning (9:00 AM–11:00 AM).

Diagnosis and remarks

This species can be recognised among other congeners by the following characters: 1) penis of male imago with laterally expanded pointed apex and small median titillator; 2) distinct abdominal colouration pattern in imago; 3) head capsule of nymph with a pair of indistinct pale spots; 4) abdominal terga of nymphs without any spine but with a longitudinal median ridge, posterior margins of each terga with row of blunt denticles. E. (P.) gibbus sp. nov. most resembles E. (P.) unispinosus Braasch, 1980 by having similar structures of mouthparts (e.g. labrum and mandibles, see Figures 4 View Figure 4 (b), 6(c) and 16(e,f)), gills ( Figures 4 View Figure 4 (j) and 6(d)) and colouration pattern of abdominal ( Figures 1 View Figure 1 (d) and 2(a)). However, E. (P.) gibbus sp. nov. can be distinguished from the latter by the absence of median unpaired spine on posterior margin of abdominal tergum ( Figure 1 View Figure 1 (e)) and the indistinct paired spots on head capsule (which distinct in E. (P.) unispinosus , Figure 1 View Figure 1 (e)).

We collected these two related species E. (P.) gibbus sp. nov. and E. (P.) unispinosus in the same stream from west Tianmu mountain. The nymphs of E. (P.) gibbus sp. nov. were found inhabiting upper sites of the stream (altitude above ca. 300 m) while E. unispinosus inhabit lower water (ca. 150–300 m).

Distribution

China (Zhejiang).