Clypeocaenis gayathri Balasubramanian & Muthukatturaja, 2020

Muthukatturaja, Marimuthu, Balasubramanian, Chelliah & Murugan, Alagumalai, 2020, Two new species of Clypeocaenis (Ephemeroptera: Caenidae) from Western Ghats, Southern India, Zootaxa 4722 (4), pp. 361-370 : 362-365

Clypeocaenis gayathri Balasubramanian & Muthukatturaja , sp. nov.

( Figures 1 , 3–16 )

Material examined. Holotype (in ethanol): mature nymph (Reg.No. ZSI–SRC/ I/E 401), India, Gayathripuzha River, Palakkad district , Kerala state, 29-XI-2018, 65 m (10º38’48” N, 76º33′47” E), collected by Balasubramanian & Muthukatturaja. Paratypes: 5 mature nymphs same data as holotype (Reg. No. ZSI–SRC/ I/E 402) .

Diagnosis. Nymph: (i) clypeus slightly protruded with two long setae, 2–3 small setae on pedicel; (ii) mandible with two rows of 5–8 long, spines; (iii) fore tibiae with two rows of ventral and two rows of lateral filtering setae; femur with bifid spines, middle tibiae with trifurcated spines apically, midtarsi with row of stout spines medially, hindtibiae with bipectinate setae distally; (iv) tracheated gill covers with spines and bifurcated ridges, gills III–VI with fringe bifid, gill III with 13 bifurcated fimbriae and 17 lanceolate setae with ridges at basal region of fimbriae; (v) gill VI with 3 bifurcated fimbriae, nine lanceolate setae on ventral margin and lack of trifurcated fimbriae; (vi) tergum II with upright, backwardly curved medial projection.

Description. Mature nymph (in 95% ethanol). Body length (without cerci): 3.0–4.0 mm in male and female nymphs; cerci lengths 1.87 mm; median caudal filament 2.5 mm; antennae lengths 1.35 mm. General body coloration washed yellow dorsally and pale yellow ventrally, young specimens generally paler; legs light to medium brown.

Head ( Fig. 1 ) length 0.81 mm, width 1.62 mm; pale yellow, eyes black, ocelli paler. Two long setae on anterior margin of clypeus and slightly protruded ( Fig. 1 ). Antennae yellowish transparent distally, inner margin of pedicel with 2–3 short setae distally. Epicranial suture paler. Two long setae with feathered margins on posterior margin of clypeal protrusion. Labrum ( Fig. 3 ) length 0.46 mm, width 0.27 mm, 1.7 times broad as long, emargination without setae and hair-like setae, anterior margin with row of long setae, 1/3 of labrum with row of long, thin setae posteriorly. Mandibles ( Fig. 4a, b ) with two rows of 5 and 8 long setae below the incisors, 1/2 of basal part of mandible chagrinated. Maxillary palp ( Figs 6a, b ) two-segmented; segment II two times longer than segment I, 1/2 of segment II covered with hairlike and other setae. Hypopharynx ( Fig. 5 ): apical margin of superlingua covered with stout spines and lingua with very short spines at apical margin. Labium ( Fig. 7 ): glossae rounded with apical spines, paraglossae covered with thin setae, labial palp three-segmented, segment III much longer than segments I and II, 2 transverse rows of stout setae at tip of distal margin, segment I with three stout setae at outer margin.

Thorax: pronotum pale yellow, margins pale brown. Anterolateral areas of pronotum produced. Mesonotum pale yellow, with black smudges between wing pads. Legs: evenly covered with scales, pale yellow with washed brown; absence of scales on macula on fore femur, middle and hind femora with scales on macula. Foreleg ( Fig. 8 ): lengths of femur/ tibia/ tarsus/ claw viz., 1.08/ 0.81/ 0.54/ 0.27 mm. Coxa with few spines on surface and long, thin spine at inner margin. Trochanter with two rows of stout spines on outer margin and 1/3 with transverse row of short spines. Femur with 4 long, stout setae at middle of inner margin and long, stout setae at 1/3 of outer margin, row of bifid stout setae at outer and distal margins. Tibia with two rows of filtering setae on lateral and ventral margins, 6 long stout spines at ventral margin. Tarsus with few monopectinate setae on ventral margin. Claw hooked with 10 denticles. Midleg ( Fig. 9 ): lengths of femur/ tibia/ tarsus/ claw viz., 1.22/ 0.81/ 0.68/ 0.32 mm. Coxa same as foreleg. Trochanter with row of 5 long setae at outer margin, femur with stout spines on outer margin and few bifid spines on dorsal surface. Tibia with trifurcated spines on apical half. Tarsus with row of stout spines medially. Claw long, slender and hooked with 10 denticles. Hindleg ( Fig. 10 ): lengths of femur/ tibia/ tarsus/ claw viz., 1.22/ 0.81/ 0.54/ 0.27 mm. Coxa, trochanter and femur otherwise same as midleg. Tibia with two prominent spines on outer margin and row of spines on inner margin, distal margin with bipectinate spines. Tarsus: inner margin with stout spines, outer margin with thin, long, bipectinations at tips of spines. Claw hooked with 9 denticles.

A bdomen: terga VI and VII pale brown, remainders pale yellow, laterally translucent. Tergum II ( Fig. 15 ) with upright, backwardly curved medial projection, posterior margin of tergum with pointed spines and surface with scales, medial projection pale brown with scales and without spines. Posterior margin of terga VII ( Fig. 16 ) with short, spatulate, bifid and pinnate bristles and terga IX with teeth on posterior margin. Sternum whitish yellow. Gills ( Figs. 11–13 ): gill I bluntly pointed, two-segmented, segment II four times longer than segment I. Gill covers ( Fig. 14 ) pale yellow, evenly covered with scales, inner margin with row of spines, outer margin with bifurcated ridges. Gills III–VI approximately triangular shaped, fringed bifid fimbriae, gill III with 13 bifurcated fimbriae and 17 lanceolate setae at basal margin; gill VI with 3 bifurcated fimbriae and nine lanceolate setae on ventral margin and lack of trifurcated fimbriae. Cerci translucent.

Etymology. The species name gayathri refers to the Gayathripuzha river, Palakad district, Kerala where the new species was collected.

Habitat. This species was found on the underside of cobbles and pebbles in medium to fast current streams and associated with Caenis sp. ( Caenidae ), Choroterpes sp. ( Leptophlebiidae ), Tricorythus sp. ( Tricorythidae ) and Baetis sp. ( Baetidae ); it possibly feeds on fine particulate organic matter available in the water current and also in the substratum.

Distribution. Southern Western Ghats, Kerala ( India).

Figures

FIGURES 1–2. Mature nymph, dorsal view. 1–Head of Clypeocaenis gayathri sp. nov., 2–Head of Clypeocaenis sharadhae sp. nov.

FIGURES 3–7. Mature nymph, Clypeocaenis gayathri sp. nov. 3–Labrum (dorsal view), 4a, b–Mandibles (dorsal view), 5–Hypopharynx (dorsal view), 6a, b–Maxillae (dorsal view), 7–Labium (dorsal and ventral views).

FIGURES 8–16. Mature nymph, Clypeocaenis gayathri sp. nov., dorsal views. 8–Foreleg, 9–Midleg, 10–Hindleg, 11–Gill I, 12–Gill III, 13–Gill VI, 14–Gill cover, 15– Tergum II, 16–Tergum VII.