Vietnamella chebalingensis Tong, 2020

Luo, Yanping, Jiang, Jian, Wang, Lili, Shu, Zufei & Tong, Xiaoli, 2020, Vietnamella chebalingensis, a new species of the family Vietnamellidae (Ephemeroptera) from China based on morphological and molecular data, Zootaxa 4868 (2), pp. 208-220 : 211-213

Vietnamella chebalingensis Tong , sp. nov.

( Figs 2–21 )

Material examined. Holotype: Female mature larva (in ethanol), CHINA, Gaungdong Province , Shixing County, Chebaling National Nature Reserve (24°42'25"N, 114°14'15"E), 29.v.2019, Lin Hong & Jian Jiang . Paratypes (in ethanol): 6 larvae same data as holotype, 3 larvae the same locality but collected on 30-31.v.2019; one larva on slides (No. 2020042923) .

Description. Mature larva (in ethanol). Body length 11.0–12.0 mm (including the outer cephalic frontal horns); cerci 7.0–8.0 mm, medial caudal filament, 9.0–10.0 mm, slightly longer than cerci. Body coloration predominantly purple black with mottled white markings ( Figs 2–3 ), body color can change in intensity depending on the life stage, the immature larvae usually light purple red ( Fig. 4 ).

Head. Vertex without tubercles. Compound eyes dark and large; ocelli covered with protruding tubercles. Two pairs of cephalic projections below the eyes, outer pairs of projections long and stout, triangular, cone-shaped without any serrated spines; inner pairs smaller, cone-like and sharp, the length slightly shorter than the half of outer pairs ( Figs 5–6 ). Antenna located between projections and approximately 1.5 times length of the outer projections. Labrum ( Fig. 8 ) small and nearly rectangle with anterior angles rounded, anterior half of dorsal surface and margins with numerous feathered setae, a densely transverse row of long, stout ciliate bristles at median, posterior half of dorsal surface smooth without setae; ventral surface with shorter setae but those near margins longer and denser. Labium ( Fig. 9 ) sub-triangular, glossae slightly shorter than paraglossae, with dense feathered setae apically; paraglossae with long feathered setae on margin; labial palpi 3-segmented and slender, basal segment approximately 2 times length of the second, apical segment shortest. Hypopharynx ( Fig. 10 ): superlinguae sub-quadrate, densely covered with long, feathered setae on margin, lingua nearly round, with densely short and fine setae on surface. Left and right mandibles slender and similar in structure, outer incisor fused to spoon-like, inner incisor (kinetodontium) forming a bunch of prostheca-like setae; prostheca consisting of a bunch of spine-like setae; left mandible ( Fig. 11 ) molar brick-like with tuft of spine-like short setae apically; right mandible ( Fig. 12 ) compared to the left, with an obvious tongue-like tooth apically and tuft of long setae under the apex of molar. Maxillae ( Fig. 13 ) slender; maxillary palpi 3-segmented, length ratio from basal to apical segments = 1:1.3:1.

Thorax. Pronotum rectangular with a pointed projection antero-laterally ( Fig. 19 ). Fore femur strongly expanded with acute teeth on ventral margin and dorsal surface with a flattened area demarcated by transverse ridge serrated with small rounded and flat setae ( Fig. 14 ); mid femur slightly expanded with a row of long setae along the dorsal and ventral margins, wider and flatter than tibia and tarsus, ratio of longest/widest = 1.8:1 ( Fig. 15 ); hind femur similar to the mid, ratio of longest/widest = 2:1 ( Fig. 16 ). All claws similar, with a small denticle sub-basally and tuft of 3–5 bowed subapical bristles ( Fig. 17 ).

Abdomen. Pairs of pointed projections present on posterior margin of tergites I–VI and VIII–X, tergite VII with only a single sharp projection posteriorly ( Figs 2, 4 , 7 , 18 ; cf. Figs 22, 24 of V. sinensis ); dorsal surface of tergites I–VI, IX–X each with a pair of nearly parallel median ridges except tergites I and X with vestigial ridges, those on tergite VII two dorsal ridges fused together at posterior margin, tergite VIII with a single dorsal ridge which is divided into two ridges near posterior margin. Gills on segments I–VII, gill I finger-like with hair-like setae ( Fig. 18 ); those on segments II–VI similar in structure ( Fig. 20 ), with dorsal and ventral lamellae, dorsal lamella with a trident-like brown markings, ventral lamella with bifurcate clusters, each with several smaller lobes; gill VII much smaller than gills II–VI and divided into three lobes, usually covered by gill VI ( Fig. 21 ). Caudal filaments dark brown except white medially, with dense lateral setae on inner and outer margins except 1/3 length of apical parts ( Figs 2–4 ).

Alate stage: Unknown.

Etymology. This new species is named after the type locality, Chebaling National Nature Reserve, northern Guangdong Province, China.

Distribution. China (Guangdong).

Diagnosis. The larva of Vietnamella chebalingensis Tong sp. nov. can be easily distinguished from that of other members of the genus by the following critical characters: (1) body purple black with mottled white markings ( Figs 2–3 ); (2) inner cephalic projection relatively long ( Figs 5–6 ), length ratio of outer cephalic projection to the inner = 2:1 (whereas the ratio is at least 4: 1 in other Vietnamella species); (3) length ratio from basal to apical segments of maxillary palpi = 1:1.3:1 ( Fig. 13 ); (4) abdominal tergites I–VI and VIII–X each with a pair of pointed projections posteriorly, but tergite VII bearing a single projection ( Fig. 18 ); (5) all claws each with tuft of 3–5 bowed subapical bristles ( Fig. 17 ). This new species is most similar to V. maculosa Auychinda, Sartori & Boonsoong, 2020 and V. nanensis Auychinda & Boonsoong, 2020 in appearance by sharing the mottled color pattern in the body and legs, but it can be separated from the latter by above mentioned characters.

Figures

FIGURES 2–4. Habitus of Vietnamella chebalingensis Tong, sp. nov. (2) Dorsal view; (3) ventral view; (4) dorsal view of immature larva.

FIGURES 5–7. Vietnamella chebalingensis Tong, sp. nov. (5) Dorsal view of head, pronotum and forelegs; (6) ventral view of head, pronotum and forelegs; (7) abdominal tergites I–X.

FIGURES 8–13. Mouthpart of Vietnamella chebalingensis Tong, sp. nov. (8) Labrum (dorsal view); (9) labium (ventral view); (10) hypopharynx; (11) left mandible; (12) right mandible; (13) maxilla.

FIGURES 14–17. Vietnamella chebalingensis Tong, sp. nov. (14) Foreleg femur; (15) midleg; (16) hindleg; (17) foreleg claw.

FIGURES 18–21. Vietnamella chebalingensis Tong, sp. nov. (18) Abdominal tergites I–X; (19) pronotum & mesonotum; (20) gill VI; (21) gill VII.

FIGURES 22–24. Habitus of Vietnamella sinensis (Hsu, 1936) (Voucher specimen for COI sequence). (22) Dorsal view; (23) ventral view; (24) abdominal tergites I–X.