Platybaetis selvai Kubendran, Vasanth & Subramanian, 2021

Kubendran, T., Vasanth, M., Subramanian, K. A., Jabeen, Fatima, Sivaramakrishnan, K. G. & Mitra, Pallabi, 2021, A new species and new record of the genus Platybaetis Müller-Liebenau, 1980 (Ephemeroptera: Baetidae) from Eastern Himalaya, India, Zootaxa 5047 (5), pp. 575-582 : 576-581

Platybaetis selvai Kubendran, Vasanth & Subramanian sp. nov.

( Figs 1–30 )

Material examined. Holotype: 1 mature larva, INDIA, Arunachal Pradesh, Dibang Valley district, Tangon stream, 27.44119°N, 94.23509°E, 275 m, 15.vii.2018, Coll. Pallabi Mitra (Reg. No. HARC /I-7197) . Paratypes: 2 larvae (1 larva on slide: mouthparts, legs & gills) same data as holotype (Reg. No. HARC /I-7198) .

Description. Larva. ( Figs 1–2 ) Length: Body 9.5–9.8 mm. Cerci 6.0– 6.2 mm, length of the median caudal filament 10–11 segments ( Fig. 3 ); antennae 1.5–1.6 mm ( Fig. 4 ).

Head. Flattened; slightly wider than long; brownish yellow with irregular pale markings, well visible, vertex and frons with dark markings with three black ocelli. Antennae brownish, scape thick and short setae on anterior margin, broader than wide, pedicel cylindrical and flagellum with small hair-like setae on each segment ( Figs 4 & 28 ). Hind margin of head without incision ( Fig. 2 ). Labrum ( Figs 5–6 ) rounded, 1.5 times wider than long; distal margin with row of apically hair-like setae, dorsal surface with hair-like setae and arc of setae with 1+3 stout medium spine-like setae. Hypopharynx ( Fig. 7 ) with long thin setae. Right mandible incisors with 6 denticles, prostheca robust, tuft of setae reduced to the apex of the mola ( Fig. 8 ). Left mandible incisors with 6 denticles; prostheca with small denticles apically; mola with thumb-like long apical prolongation ( Figs 9–10 ). Basal half with short simple setae scattered over dorsal surface. Maxillae with two distal dentisetae and 3 canines; setae of inner dorsal row 1.5 times longer than setae of inner ventral row. Palps 2-segmented; second segment slightly longer than first segment, second segment of inner margin slightly curved, outer margin straight; segment 2 with small rounded projection at apex ( Fig. 11 ). Labium with glossae longer than paraglossae; glossa with 2 blunt setae at apex ( Fig. 13 ), stout setae apically; a few small setae on dorsal margin; 8–9 long, stout setae on inner margin; paraglossa with apically 3 rows of long, stout setae; palps 3-segmented, segment III rounded with numerous short stout acute setae ( Fig. 12 ).

Thorax. Yellowish brown ( Fig. 1 ). Pronotum nearly as broad as head capsule ( Figs 1–2 ); pronotum posterolateral margin rounded. Hindwing pads reduced, small ( Fig. 30 ). All legs generally whitish with brownish yellow ( Figs 14–16 ). Foreleg ( Fig. 14 ): tibia 1.6x femur length; tarsus 2.4x shorter than tibia; dorsal margin of tibia with a row of long, feathered setae, some short scattered setae along with margin ( Fig. 18 ); apex of femora rounded, inner margin with row of small stout setae. Tibia dorsal margin with a row of long, feathered and simple setae scattered over the surface. Tarsi with a dorsal row of long setae; two ventral short setae ending with one long fine bristle near apex. Claw with a single row of 7–8 robust denticles, size increasing in size towards apex; with 4–5 apical stripes, subapical setae absent ( Fig. 17 ). Middle and hind leg generally same as foreleg ( Figs 15–16 ).

Abdomen. Coloration of terga ( Figs 1–2 ); terga I–IV light brown, V pale yellow, VI–VII dark brown, VIII–X pale yellow; terga I–X posterior margin with rounded ‘U’ shaped spines ( Figs 19–20 ). Sterna I–X pale yellowish. Gills present on segments I–VII, simple, leaf-like and rather broad; with dark tracheation; margins with minute setae ( Figs 21–27 ). Paraproct distally not expanded without marginal spines. Surface scattered with small ‘U’ shaped scale bases, fine simple setae and micropores ( Fig. 28 ). Posterolateral extension (cercotractor) with 8–9 small spines ( Fig. 28 ). Cerci shorter than the body length; paracercus composed of 10–11 segments ( Fig. 3 ).

Imago: Unknown.

Etymology: The species name “ selvai ” is abridged patronym of Dr. C. Selvakumar who has significantly contributed to Indian Ephemeroptera taxonomy.

Distribution: India (Arunachal Pradesh).

Diagnosis: Platybaetis selvai sp. nov. can be differentiated from other species of this genus by the following combination of characters: (i) posterior margin of abdominal segments I–X with rounded ‘U’ shaped spines ( Figs 19–20 ); (ii) margins with minute setae on gills I–VII; ( Figs 21–27 ); (iii) claw with 7–8 denticles ( Fig. 17 ); (iv) paracercus composed of 10–11 segments ( Fig. 3 ); and (v) hindwing pads reduced, small ( Fig. 30 ).

Ecology. Larvae of P. selvai sp. nov. occurred in a small stream (Tangon, 1.5–2 m wide) on surface of flat rocks. This stream is characterized by medium water temperature (21°С at the time of sampling) and mainly pebbles and silt particles at the bottom of the stream. The locality is densely covered with the canopy of riparian vegetation at low altitude in the Dibang Valley, district of Arunachal Pradesh. Larvae were associated with Baetis sp. , Heptageniidae ( Afronurus sp. , Notacanthurus sp. ) and Hydropsychidae (Trichoptera) .

Figures

FIGURES 1–4. Platybaetis selvai sp. nov., Larva. 1. Dorsal view (mature larva); 2. Dorsal view (immature larva); 3. Posterior part of the abdomen ventral view; 4. Head ventral view.

FIGURES 5–13. Platybaetis selvai sp. nov., Larva. 5. Labrum; 6. Labrum closer view; 7. Hypopharynx; 8. Right mandible; 9. Left mandible; 10. Left mandible closer view; 11. Maxilla; 12. Labium; 13. Glossae with setae.

FIGURES 14–20. Platybaetis selvai sp. nov., Larva. 14. Fore leg; 15. Middle leg; 16. Hind leg; 17. claw; 18. Femur feathered setae on anterior margin; 19–20. Abdomen posterior margin tergum V.

FIGURES 21–30. Platybaetis selvai sp. nov., Larva. 21. Gill I; 22. Gill II; 23. Gill III; 24. Gill IV; 25. Gill V; 26. Gill VI; 27. Gill VII; 28. Paraproct; 29. Antenna; 30. Hindwing pad.