Polyplocia orientalis Nguyen & Bae, 2003

Kwanboon, Sedtawut, Boonsoong, Boonsatien & Suttinun, Chanaporn, 2023, Taxonomic review of the Oriental genus Polyplocia Lestage, 1921 (Ephemeroptera, Euthyplociidae), with two new records for Thailand, ZooKeys 1179, pp. 197-217 : 197

Polyplocia orientalis Nguyen & Bae, 2003

Figs 4 , 5 , 6

Polyplocia orientalis Nguyen & Bae, 2003a: 280, figs 1-2, original description (nymph).

Polyplocia orientalis ( Gonçalves and Peters 2016: 558, nymph).

Polyplocia spp. ( Gonçalves and Peters 2016: 558, possible nymph (Thailand)).

Polyplocia orientalis ( Zheng et al. 2023: 2, figs 1-9, male and female imago, egg, nymph).

Material examined.

Thailand: Eleven nymphs in alcohol, deposited in ZMKU, Chiang Rai province, Phan district, Pu Kaeng waterfall, 19°26'53.7"N, 99°41'83.6"E, 540 m, 5.III.2021, S. Kwanboon leg. Three nymphs in alcohol, deposited in VMCMU, Chiang Rai province, Phan district, Pu Kaeng waterfall, 19°26'53.7"N, 99°41'83.6"E, 540 m, 29.I.2023, S. Chanaporn leg. Two nymphs in alcohol, deposited in ZMKU, Thailand, Chiang Mai province, Chiang Dao district, Huay Mae Mae , 19°19'31.1"N, 99°58'84.6"E, 809 m, 20.XI.2018, C. Damrong leg.

Diagnosis.

Imago: i) membrane of wings transparent and colourless, and ii) T-shaped male penis with apical depression on both lobes ( Zheng et al. 2023). Nymph: i) large body size (25.0-46.4 mm), ii) yellowish abdominal sterna without anterolateral black mark, iii) spines on 1/3 of tusk length distally, and iv) apically expanded dorsal lobe of gill I ( Nguyen and Bae 2003a; Zheng et al. 2023).

Description.

Male imago. See Zheng et al. (2023).

Female imago. See Zheng et al. (2023).

Nymph. See also Nguyen and Bae (2003a) and Zheng et al. (2023).

Variability and additional description

(Thai specimens). Nymph. Male body length 17.22 mm; cerci length 11.78 mm; median filament length 10.5 mm. Female body length 27.9 mm; cerci length 18.5 mm; median filament length 16.2 mm.

Head. Length 2 × of maximum width; narrower than pronotum. Compound eye black on dorsolateral margin. Antenna 8.8 mm in length; scape with at least three short setae.

Mouthpart. Labrum (Fig. 5A ) shallow, concave at anteromedian margin, with a tuft of dense long, simple setae; anterior margin with a row of 14-16 long, simple setae; dorsal surface with long, fine setae and short, simple setae scattered over area. Mandibular tusks (Fig. 5E ) strongly arched inward (18.6° in curvature); a row of simple setae on base of tusks; ventrally almost bare. Right mandible without prostheca. Left mandible with prostheca as long as incisors, truncate, broader apically. Maxillary palp (Fig. 5D ) 1st segment with a few of long, fine setae on outer margin; 2nd segment with lateral long, hair-like setae in both inner and outer margin; 3rd segment long, at least 6 × longer than wide, apically pointed, with numerous of long, hair-like setae on lateral inner margin and scattered over half of segment apically. Hypopharynx (Fig. 5B ) lingua cordiform; superlingua extended laterally. Labium (Fig. 5C ) paraglossae articulate above glossae; labial palpi 1st segment with long, hair-like setae on outer margin and fine, simple setae on inner margin; 2nd segment with long, hair-like setae on outer margin; 3rd segment much broader than 2nd segment, apically truncated almost straight with a tuft of stout, simple setae, with long, hair-like setae on outer margin and fine, simple setae on inner margin.

Legs. Ratio of forelegs: midlegs: hindlegs 1:0.7:0.7; ratio of foreleg segments 1:1.2:0.7:0.4; ratio of midlegs segments 1:1:0.4:0.2 with moderately developed setae; ratio of hindleg segments 1:0.6:0.2:0.1, lack setae on femora.

Female subimago. Egg. (Fig. 6 ) Dissected from female subimago; length 272 μm, width 214 μm; oval-shaped; no polar caps or other attachment structures; rough chorionic surface, mesh-like with irregular raised ridges (Fig. 6B ); two visible linear micropyles formed with micropyle canal on the surface (Fig. 6C ).

In this study, Thai Polyplocia orientalis showed some variation in these characters combined: i) Labrum slightly concave on anterior margin, nearly straight, ii) tusks cylindrical pointed apically, strongly arched inward (18.6° curvature) and outer margin with 7-9 larger spines on 1/3 of tusk length distally, and iii) eggs oval-shaped with two visible micropores.

Distribution.

China (Yunnan), Vietnam (Dak Lak, Lam Dong, Thua Thien Hue), Thailand (Chiang Rai, Chiang Mai, Phrae, Phayao, Nan) ( Nguyen and Bae 2003a, Gonçalves and Peters 2016, Zheng et al. 2023, this study).

Figures

Figure 4. Habitus of nymph of Polyplocia orientalis: A female mature nymph (dorsal view) B female mature nymph (ventral view) C male mature nymph (dorsal view) D male mature nymph (ventral view).

Figure 5. Polyplocia orientalis, nymphal morphology: A labrum (dorsal view) B hypopharynx (ventral view) C labium (ventral view) D left maxilla (ventral view) E mandibular tusk. Scale bar: 0.5 mm.

Figure 6. Polyplocia orientalis, SEMs of egg structures: A general outline of egg B chorion surface C micropyle.