Thraulus thiagarajani Balasubramanian and Muthukatturaja, 2019

Balasubramanian, Chellaiah & Muthukatturaja, Marimuthu, 2019, A new mayfly Thraulus species (Ephemeroptera: Leptophlebiidae) from Peninsular India, Zootaxa 4638 (1), pp. 136-142 : 137-141

Thraulus thiagarajani Balasubramanian and Muthukatturaja , n. sp.

Type series. Holotype (in ethanol): 1 male imago, INDIA, Payaswini river, Sampaje, Kodagu district , Karnataka state, 30-III- 2018, 152 m (12º29′.47″ N, 75º33′.32″E), collected by C. Balasubramanian & M. Muthukatturaja (Reg. No. SRC/ ZSI Reg. No. I /E 397 to 399)

Paratypes (in ethanol): 17 mature nymphs, 9 male imagoes and 6 female imagoes, same data as holotype deposited in Zoological Survey of India (Reg.No. SRC/ ZSI. I/E 397 to 399)

Mature Nymph ( Fig. 1 ). Dimensions (mm): Body length (excluding cerci): 7.0–9.0 in male and female nymphs; cerci length 1.25 times longer than body length. General body coloration blackish brown to brownish yellow, yellowish brown to blackish brown to brown dorsally and pale to yellowish brown ventrally, young specimens generally light brown to paler; legs brown to yellowish brown, with ½ basal brownish femora. Size range of specimens examined: head width 0.38–0.48.

HEAD length 2.0, brownish yellow; evenly with brown between eyes and ocelli, around antennal sockets, anterior margin of clypeus and distal end of the head; posterior margin concavely rounded, lateral margins blackish brown. Eyes: black, oval; 0.07 length of the eye 2 times greater than the width. Antennae 3.0–4.0 with scape, pedicel, and base of flagellum light yellow, middle of pedicel washed lightly with yellowish brown. Mouthparts ( Figs. 1-5 ) brownish yellow, washed evenly with brown especially on lateral margins: Labrum ( Fig. 1 ) with a rectangular mesal emargination anteriorly; width 0.7 length 0.19; a row of dorsal thick setae on the mesal emargination; a row of thin long setae just anterior to1/2 of labrum; lateral margins with few setae, a row of stout spines below 1/3 of the anterior margin of labrum just inward, width slightly greater than clypeus. Mandibles ( Fig. 2a & 2b ) with lateral margin smoothly rounded; lateral setae sparse, thin, 9 near middle of lateral margin of left mandible; Right mandible with 7 thin setae in middle of the lateral margin, prostheca of left mandible with five thin spines, in right mandible two thick spines of prostheca with two thin spines. Below the molar, 8 hairy setae present, incisor with trident tip and the inner incisor slightly serrated. Maxillae, tip of the galea with a simple comb like structure and cluster of numerous feathered setae, below the galea a row of 12–18 peculiar comb like setae present ( Fig. 3a & 3b ) and it gives a comb like structure at the tip of the galea, below the lacinia numerous feathered setae ends with a single thin setae, length of the apical: middle: basal segment 0.016: 0.13: 0.12. middle segment is larger than other segments, lateral margin and distal end of the apical segment with thin long hairy setae, middle segment has few setae, no setae in basal segment. Labial palpi ( Fig. 5 ) with inner and outer margins of segment 1 with few thin spines, washed evenly with brown, length of the segments I: II: III, 0.24: 0.16: 0.19, 1 st segment larger and broader than other segments, segment II with few setae evenly and III with tuft of setae at the distal end. Glossa with thick plate like setae on the ventral margin few on dorsal surface, paraglossa with numerous setae ventrally few dorsally. Hypopharynx yellowish brown, sub-lingua with numerous thin spines ventrally, lingua with tiny hairy setae on the ventral and dorsal surface ( Fig. 4 ).

Thorax: Brownish yellow. Hindwing pads covered by forewing pad in dorsal view, margins dark brown, 2 yellowish brown submedian maculae in center. Forelegs ( Fig. 6a ) size of femora: tibia: tarsi: claw 0.61: 0.63: 0.22: 0.097, Coxa brownish yellow, washed evenly with dark brown; lateral margin with 3 setae. Trochanters with anteri- or and posterior surfaces dark brown, lateral and mesal surfaces brownish yellow; with basal row of feathered setae and a shorter sub-apical row of stout spines. ½ of the basal femora with dark brown, apical 1/2 washed evenly with yellowish brown. Tibiae brownish yellow, apex washed evenly with dark brown; ventro-lateral margin flattened, densely covered with a row of feathered setae and with a row of stout spines, hind tibia has few thin setae dorsally. Tarsi light brownish yellow, 3 tiny hairy setae present dorsally. 14 denticles in the claws ( Fig. 6b ). Middle leg ( Fig. 7a ): size of femora: tibia: tarsi: claw 0.68: 0.68: 0.19: 0.087, colouration as in foreleg: Coxa and Trochanters without setae. Tibiae of inner margin covered sparsely with very short, tiny setae distal end of the tarsi has a stout spine, 11- 14 denticles in the claw ( Fig. 7b ). Hind leg ( Fig. 8a ): size of femora: tibia: tarsi: claw 0.73: 0.75: 0.19: 0.097, Coxa with a row of spines ventrally and trochanter with few feathered setae and a single spine dorsally, ventero-lateral margin of femora covered with stout spines and prominent feathered setae, Tibiae densely covered with short fine setae, base and lateral margin with few spines, median tibia with peculiar trifurcate setae and dorsolateral margin of tibia with few feathered setae and few stout spines, 12 denticles in the claw ( Fig. 8b ).

ABDOMEN ( Fig. 9 ): Terga brownish yellow, washed evenly with yellowish brown, abdominal segments 2-9 with a brownish yellow stripe longitudinally; terga 2-8 with brownish yellow anterior margins; spiracular areas white. Sterna light yellow; sterna 1-8 with paired sublateral maculae; posterior margin of sternum 8 and all of sternum 9 washed evenly with dark brown, tergum 8 and 9 ochraceous and accuminate; mesal margin of posterolateral spines on segments 8 and 9 dark brown; lateral portions of posterior margins narrowly dark brown, terga 8 and 9 brown, posterolateral spines of terga 8 and 9 larger. Gills ( Fig. 10-12 ) washed evenly with dark brown: gills on abdominal segment 1 with a long lanceolate dorsal lamella and an oval ventral lamella with well developed tracheation ( Fig. 10 ); margin of apical 2/3 of lamella lined with fimbriae; lamellar length ca. 3 and 1/2 times width; lengths of fimbriae increase apically. Gills on abdominal segments 2-7 with oval dorsal and ventral lamellae; lamellae as in gills on abdominal segment 1 except fimbriae cover all margins except extreme basal portion. Caudal filaments brown basally, fading to light brown towards apex gill 7 ( Fig. 12 ) lamllate and very small gill when compare to other gills, poorly developed tracheation. No hairy setae on caudal filaments.

Male Imago ( Fig. 2 ). Dimensions (mm): Length: Body, 7.0; forewings, 8.0; hindwings, 1.73. Width: forewings ( Fig. 13 ), 2.3; hindwings ( Fig. 14 & 15 ), 1.19; Cerci 2.0, Median Terminal filament 3.0; Upper portion of eyes red to yellowish-brown, lower portion of eyes black.

Head ( Fig. 18 ) length 1.13, brown, anterior margin darker. Antennae light brown. Basal half of ocelli black to brown, apical half paler; dorsal diameter of eye, 0.77; distance between compound eyes 0.

Thorax yellowish-brown, carinae light brown, sutures pale yellow; lateral and near posterior margin of pronotum; large yellowish brown maculae on pronotum surroundings inner parapsidal sutures, and near posterolateral margin of scutum; mesoscutellum and metascutellum washed lightly with pale yellow. Wings: longitudinal and cross veins of fore and hindwings light to brotranslucent; membrane of fore and hindwings pale yellowish-brown; base and membrane of cells C and Sc of forewings and base of hindwings darker. Rs forked 1.37 distance from the base of MA forked at 0.6 distance from base of vein to wing margin; vein MP forked at 0.25 distance from base of vein to margin, fork symmetrical 2 inter-calleries present between CuA and CuP ( Fig. 13 ). The hind wing much smaller than forewings; the costal projections bluntly rounded, apex of projection situated at 0.6- 0.7 distance from the base to apex of wings; apex of the wings blut with apical and posterior area expanded slightly ( Fig. 14 & 15 ). Legs: ratios of segments in forelegs ( Figs. 21-23 ) 0.24; 0.12; 0.78; 1.19; 0.65. Coxae base with dark brown band; Trochanter with single dark brown at base. fore femora with dark brown; length of femora 1.5 folds smaller than fore tibia, mid and hindlegs with equal length of femora and tibia. Mid and hindlegs with 2 transverse dark band at middle and subapical part of femora; wide, transverse, dark brown median and apical bands; base of tibiae pale yellow.

Abdomen ( Figs. 19 & 20 ): segments 1-7 hyaline; washed with light brown; segments 8-10 light yellowishbrown; posterior margin of terga ( Fig. 19 ) 1-10 brown terga 1-9 with sublateral, wide, longitudinal, brown bars; sterna ( Fig. 20 ) pale yellow; spiracles and trachea washed with brown; ganglia of sterna 1-4 light yellowish-brown. Genitalia: forceps yellowish-brown ( Fig. 16 ) 1.46; penes pale yellow to translucent ( Fig. 17 ) 0.78 divided, slender and tubular, length of penes was 0.5 length of forceps, apex of each penes lobe rounded genitalia pale yellow washed with brown, segments 2 and 3 of forceps and penes paler, lateral margin of penes with spines, lateral margins of styliger plate dark brown. Caudal filaments pale yellow, annulations at articulations pale yellow.

Female Imago (Fig: 2). Dimensions (mm): Length: body 4.7; forewings, 6.5; hindwing, 1.52. Width: forewings, 1.6; hindwing, 0.99; Cerci 1.83, Median Terminal filament 2.78; eyes black.

Head length 1.33, light brown, carinae washed with yellow. Antennae light brown. Basal half of ocelli dark brown, apical half white; dorsal diameter of eye, 0.37; distance between compound eyes 0.92.

Thorax color and markings as in male imago, except pronotum and mesonotum washed with yellow, mesoscutellum washed with yellow. Wings: longitudinal veins of fore and hindwings pale yellow, cross veins and membrane hyaline; apical cells C and Sc of forewings translucent white. Legs: foreleg 0.26; 0.14; 1.46; 1.19; 0.59 markings as in male imago; femora pale yellow and dark brown bands obscured; remainder of legs washed with yellow.

Abdomen yellowish brown; terga 1-10 with brown markings; spiracles and trachea washed with yellowishbrown; sterna 1-7 with light brown color markings as in figure; sternum 9 pale yellowish-brown. Caudal filaments pale, annulations at articulations pale yellow.

Egg. ( Fig. 24 , dissected from female body) Dimensions (µm): Length 113.61, breadth 69.56. Egg ovoid; exochorion with flower shaped rid ges; no visible micropyle on chorionic surface.

Etymology. The species named thiagarajani in honor of Karumuttu Thiagarajan Chettiyar, founder of Thiagarajar group of institutions, Madurai.

Ecology. This species was found in the silt soil, cobbles and pebbles covered places of the stream in middle to fast current, associated with Ephemera sp, Choroterpes sp, Isonychia sp. Indialis sp. and Baetis sp., possibly to feed on fine particulate organic matter available in the water current and also in the substratum.

Figures

FIGURE 24. Thraulus thiagarajani. nov. 24—SEM image of Egg.

FIGURES 1–12. Thraulus thiagarajani. nov. 1—Labrum, 2a—Left Mandible, 2b—Right Mandible, 3a—Left maxilla, 3b— Right Maxilla, 4—Hypopharynx, 5—Labium, 6a—Foreleg, 6b—fore claw, 7a—Midleg, 7b—Mid claw, 8a—Hindleg, 8b— Hind claw, 9—abdomen, 10—Gill I, 11—Gill IV, 12—Gill VII.

FIGURES 13–23. Thraulus thiagarajani. nov. 13—Forewing, 14—Hindwing, 15—Hindwing enlarged, 16–Male genitalia, 17—Penes, 18—Head, 19—Tergum, 20—Sternum, 21—foreleg, 22—Midleg,, 23—Hindleg.