Rhoenanthus (Rhoenanthus) tungaiensis Balasubramanian and Muthukatturaja, 2019

Balasubramanian, Chelliah, Muthukatturaja, Marimuthu & Anbalagan, Sankarappan, 2019, A new mayfly species of Rhoenanthus (Ephemeroptera: Potamanthidae) from Peninsular India, Zootaxa 4664 (2), pp. 293-300 : 294-299

Rhoenanthus (Rhoenanthus) tungaiensis Balasubramanian and Muthukatturaja , new species

( Figs.1– 12 )

Material examined Holotype: male imago (Reg.No. SRC/ ZSI-I/E 391), INDIA, Tunga River, Sringeri, Chikkamagalore district , Karnataka state, 01-IV- 2018, 669 m. (13º36′.27″ N, 75º19′.89″ E). Collected by Balasubramanian & Muthukatturaja . Paratypes: 8 male imagoes, 2 female imagoes and 35 mature nymphs (Reg.No. SRC/ ZSI-I/E 392 & 393), same data Holotype is deposited in Zoological Survey of India (Southern Regional Centre), Chennai .

MATURE NYMPH ( Fig.12 ): Body length (excluding cerci): 19–21 in male and female nymphs; cerci length half times longer than body length. General body coloration yellow to dark brown, yellowish brown to dark brown dorsally and pale to yellowish brown ventrally, young specimens generally paler; legs light to medium brown.

Head: Brown with cranial and epicranial sutures pale. Three crescent shaped ocelli present; dorsal diameter of male compound eyes 1.05 mm, female compound eyes 0.59 mm– 0.61 mm, distance between compound eye 1.86 mm; Antenna 1.3 times longer than head width, flagellum medium to light brown. Labrum ( Fig. 1 ) 2.5 times wider than long, with smooth anterior emargination; dorsal face covered medially by 2 rows of long feathered setae; dorsal setae with feather structure; anterior margin with a row of small thin setae along with a row of mono pectinate (feathered on one side) setae and bipectinate (feathered on both side) setae at emargination. Mandibles slender with few thin setae in outer margin, mandibular tusks 0.8 times longer than head length ( Fig. 12 ), outer incisor of right mandible ( Fig. 5b ) with 3 large and 3 small teeth; inner incisor with 2 teeth and line of setae laterally; prostheca bifid with sharp subapical spines, comprising a tufts of hairs ( Fig. 5b ); a tuft of hairy setae between mola and prostheca; ten long setae below the molar; mandibular body with row of stout yellowish brown setae at mesal margin; outer margin with 20–22 scattered blunt setae, 13–15 spine-like setae and 10–12 hair-like long setae; apex of left mandibular tusk ( Fig. 5a ) with two thin setae; incisors with three teeth; no thin setae, between mola and prostheca, no tuft of hairy setae. Hypopharynx ( Fig.2 ) with lingua apically truncate and covered with thin setae; super-linguae with two basal rows of sharp setae and covered apically with long simple setae. Maxillae ( Figs. 4a & 4b ) slender, 2 indented dentisetae with 7–10 serrations, and 3 long setae on inner apical part and a small row of long thin setae at crown; inner margin from apex to base of lacinia with ca 22 long monopectinate setae ventrally and 3 long simple setae dorsally; segment I of maxillary palp 1.7 times longer than segment II; maxillary palp with 5–8 simple setae; cardo and stipes of the maxilla with numerous thin setae dorsally. Labium ( Fig. 3 ): labial palp of segment III convex, inner margin covered with simple stout setae, 1.53 times longer than segment II, lengths of segments I–III (mm) = 0.54 /0.35 /0.57; paraglossae densely covered with spine like setae on ventral surface; glossa with similar setae ventrally.

Thorax: medium brown to dark brown; prothorax with two anterolateral dorsal tubercles, meso and metathorax each with two anteromedial tubercles. Legs: yellow to brown, with a row of 6–9 thin setae on distal end of coxa; a row of simple setae over the trochanter; three medium to dark brown stripes at femora; length ratio range of foreleg femur: tibia: tarsus: claw (mm) = 3.0–3.2 / 3.0–3.2 / 1.3–1.5 / 0.02–0.03; midleg femur: tibia: tarsus: claw (mm) = 2.2–2.3 / 1.8– 2.0 / 0.7–0.8 / 0.02; hindleg femur: tibia: tarsus: claw (mm) = 3.0–3.2 / 2.3–2.5 / 0.9–1.0 / 0.02–0.03; fore femur ( Fig. 6 ) 2.9 times longer than its greatest width; outer margin covered by stout and long setae, inner margin with a short row of stout and long setae; mid femora similar to that of fore femur with few stout yellowish brown setae dorsally; apex of hind femur with clump of prominent bipectinate setae ventrally; mid and hind femora 1.6–1.8 times longer than the greatest width ( Figs. 7 & 8 ); dorsal and inner margins of femur with a row of long and stout setae; tibia with a row of long and stout setae on dorsal and lateral margin. Tarsal claw simple, hooked with tufts of setae at the base, 2.5 times longer than its greatest width.

Abdomen: Yellow to brown, markings with dark brown; terga with no scattered bifurcate plumose setae on surfaces, with setae slightly distributed along margins; well-developed apically pale posterolateral projections present on terga III–IX, with largest projection on tergum IX; terga I–X each with inverted bell shaped marking, two pale anteromedial spot; sterna pale yellow, with no distinct pale spots anteromedially on segments II–VIII. Terminal filament is subequal or slightly longer than cerci, with long setae at junction of each segment. Gills ( Figs. 9-11 ) white with medium to dark brown tracheae, gills I–VII attached laterally, Gill 1 single, segmented, basal segment 0.67 mm; apical segment 1.03 mm, with numerous hair like setae. Gills II- VII composed of well developed bipectinate fibrillae with lamella, well marked tracheation and a tuft of dark brown fibrillae, gill III with 46–48 marginal fibrillae on dorsal lamellae, and 35–37 on ventral lamellae.

MALE ADULT: Length of body 14 mm, length of fore wing 12.5 mm, width of forewing 6.0 mm, hind wing length 6.0 mm, width of hind wing 3.0 mm; dorsal diameter of compound eyes 0.78 mm; distance between compound eyes 0.10 mm.

Head ( Fig. 17 ). Color yellowish brown. Compound eyes blackish yellow in alcohol, large, nearly contiguous (ES=0.14). Relative size of compound eyes of mature larvae was measured by the formula ES= B/D. where ES: compound eye size, B: shortest distance between compound eye, D: longest dorsal diameter of a compound eye ( Bae & McCafferty, 1991).

Thorax: Color whitish brown to brown: nota somewhat darker than pleura and sterna. Forewings ( Fig. 13 ) transparent, with pinkish brown to brown stained marks variously developed at base of forks; longitudinal veins yellowish brown to brown; costal cross veins reddish brown and infuscated, other cross veins purplish brown and infuscate, numbering ca 30 between Sc and R 1; 21 between R 1 and R 2; MAs 0.75 x length of MA 1; between MP 2 and CuA a large cell present; Cu regions with 4 intercalaries (3 forked): A 1 forked once. Hind wings ( Fig. 14 ) transparent, with brown stained marks variously at base of forks: longitudinal veins brown; Cross veins light purplish brown and infuscated in central area: intercalaries same as forewing; costal projection acute (>90°): base of R 1 not arched (ca.110°) toward Sc. Forelegs yellowish; middle region of the fore tibiae and fore tarsal segment 4 and 5 brown; middle legs and hind legs pale yellow; claws dark brown.

Abdomen: terga ( Fig. 16 ) I-X each pinkish yellow, with dark brown, broad mid longitudinal inverted bell shaped markings containing a pairs of pale trabeculae (rod-like marking) outwards, with pair dark brown, broad stripes running from anterolateral corner to median posterior margin and with single narrow, elongated, spots ar- ranged on lateral margin. Sterna ( Fig. 15 ) I–X each yellow, with 2 pairs of dark, median tear drop spots, sub median spots (anterior pair larger and more widely separated) and pair of narrow, longitudinal, lateral stripes. Genital forceps ( Fig. 18 ) pale yellow; penes with ventral surface pale yellow, dorsal surface light brown, apex of penes bifurcated dorsoventrally and rounded apically. Cerci pale yellow to brown relatively long (1.92 x length of body); terminal filament rudimentary 0.04 x length of cerci.

FEMALE ADULT: Length of body 15.0 mm, length of fore wing 21.0 mm, width of forewing 5.0 mm, Hind wing length 4.0 mm, width of hind wing 3.0 mm; forelegs 2.1 mm, cerci 17 mm, median terminal filament 1.0 mm; dorsal diameter of compound eyes 0.78 mm; distance between compound eyes 1.2 mm.

Head: Color brownish yellow. Compound eyes black in alcohol, medium, widely separated (ES=0.6)

Thorax: prothorax with brownish yellow to brown, longitudinal, lateral stripes on notum and pleura. Forewings with brownish brown, infuscated, costal cross veins reddish brown and with 4 cubital intercalleries 4 (3foreked); other venation as in male. Hind wings with acute costal projections (<90 degree). Fore legs pinkish brown to yellow, fore tibiae pinkish brown to yellow, tarsal segment 5 reddish brown, claw bifid, dark brown. Fore tarsal segments 1-4 pale yellow, mid and hind legs pale yellow; fore tibiae 0.9 x length of foreleg, 1.05 x length of fore tarsi.

Abdomen: Color pattern as in male. Cerci pale yellow to brown, with dark band at each suture: median terminal filament brown, rudimentary, 0.07 x length of cerci.

Etymology: The species name tungaiensis refers to the locality name, Tunga River, where the new species was collected.

Ecology: This species was found in the loose soil places at boundary of the stream in middle to fast current, associated with Ephemera sp. possibly to feed on fine particulate organic matter available in the water current.

Figures

FIGURE 12. Nymph of Rhoenanthus (Rhoenanthus) tungaiensis sp. nov., dorsal view

FIGURES 1–5. Nymph of Rhoenanthus (Rhoenanthus) tungaiensis sp. nov. 1, Labrum (dorsal view); 2, Hypopharynx (dorsal view); 3, Labium; 4a, Left Maxilla; 4b, Right maxilla; 5a, Right mandible (dorsal view); 5b, Left Mandible.

FIGURES 6–11. Nymph of Rhoenanthus (Rhoenanthus) tungaiensis sp. nov. 6, Foreleg; 7, Midleg; 8, Hindleg; 9, Gill I; 10, Gill III; 11, Gill VII.

FIGURES 13–18. Adult of Rhoenanthus (Rhoenanthus) tungaiensis sp. nov. 13, Forewing; 14, Hindwing; 15, Abdominal sterna IV-IX; 16, Abdominal terga IV-X; 17, Head; 18, Male genitalia.