Caenis maduraiensis Balasubramanian and Muthukatturaja, 2021

Muthukatturaja, Marimuthu & Balasubramanian, Chellaiah, 2021, A new species of Caenis Stephens, 1835 (Ephemeroptera: Caenidae) from Tamil Nadu, Southern India, Zootaxa 4980 (2), pp. 366-372 : 367-371

Caenis maduraiensis Balasubramanian and Muthukatturaja , new species

( Figs. 1–3 , 5–30 )

Type material. Holotype (in ethanol): male imago (reared from nymph) (Reg.No. SRC/ ZSI-I/E 469) from India, Vandiyur pond, Madurai district , Tamil Nadu state, 9.viii. 2019, 124 m, 09°54’51” N, 78°10’52” E, Balasubramanian & Muthukatturaja Cols . Paratypes (in ethanol): one female imago (reared from nymph) (Reg.No. SRC/ ZSI-I/E 470) and 5 mature nymphs (Reg.No. SRC/ ZSI-I/E 471), same data as holotype. Balasubramanian & Muthukatturaja Cols .

Additional material ( ZMTC). 156 male imago (reared from nymph), 254 female imago (reared from nymph) and 245 mature nymphs, India, Vandiyur pond, Madurai district , Tamil Nadu state, 19.viii. 2019, 124 m, 09°54’51” N, 78°10’52” E, Balasubramanian & Muthukatturaja Cols .

Diagnosis. Caenis maduraiensis sp. nov.: Nymph: (i) anterior margin of labrum with row of long bipectinate setae laterally and a group of highly fringed setae behind emargination; (ii) fore femora with transverse row of bifid spines; middle and hind femora with sparse bifid spines; (iii) hind claw long, slender and hooked with row of denticles; (iv) abdominal tergum II with pointed medial projection and pointed teeth on the posterior margin. Imago: (i) prosternal triangle with slightly concave sides, tip acutely pointed; (ii) tarsomere I extremely short; (iii) tarsomere II apically with tongue-shaped projections on single side; (iv) apical part of forceps narrowed to the tip, with a long apical spine, and few trichomes on surface; (v) cross veins of forewing arranged singly except in R 1 and R 4; (vi) MP forked at near 1/3 of distance from base to margin; (vii) fore tibia two times longer than femur and (viii) female subanal plate apically truncated.

Mature nymph (in 95% ethanol) ( Figs. 1 , 5–19 ): Body length (excluding cerci) 3.1–3.4 mm; cerci length 3.5–4.0 mm; median caudal filament 4.2–4.5 mm; length of head 0.4 mm; width of head 0.7 mm; antennae length 1.3 mm; length of fore femora/ tibia/ tarsi/ claw (mm) 0.7/0.5/0.3/0.2; length of middle femora/ tibia/ tarsi/ claw (mm) 0.6/0.37/0.25/0.18 and length of femora/ tibia/ tarsi/ claw (mm) viz., 0.65/0.6/0.4/0.15. General body coloration yellowish brown dorsally and pale ventrally, mature specimens generally paler; legs pale brown. Head brownish yellow; scape and pedicel of antennae pale brown without hairs, flagellum translucent; labrum ( Fig. 5 ) broadly emarginated, dorsum with long setae, anterior margin with row of bipectinate setae longer laterally and a group of highly fringed setae behind emargination; mandibles ( Figs. 6, 7 ) with broad incisors, outer margin of mandibles with long thin setae, left mandible with 7 thin setae below the molar, with elevated hump between prostheca and molar; maxillae ( Figs. 8, 9 ) with 3 prominent teeth on galea–lacinia, ventral base of inner margin of galea with tuft of thin setae, distal portion of cardo with cluster of bipectinate stout setae, maxillary palp 3 segmented, segment I broad, segment I and II subequal in length, segment III longer, inner margin of segment III with row of 13 bipectinate setae; hypopharynx ( Fig. 10 ): anterior margin of lingua with long setae, superlingua with small hair-like setae at anterior margin; labium with glossae ( Fig. 11 ) ovate with stout spines at outer margin, mesal margin of glossae with thin setae, inner and outer margin of paraglossae with thin spines directed anteriorly, labial palp 3 segmented, segment II slightly longer than segment I, segment III short; outer margin of segment II with stout spines, outer margin of segment I with row of bipectinate setae, segment III triangular with 2 rows of stout setae ventrally, inner margin of segment III with row of stout spines. Thorax brownish yellow; lateral margins of pronotum convex, anterolateral margins with pair of spine-like setae and wider than posterolateral margins. Legs pale brown covered with scales, tibiae and tarsi light pale. Foreleg ( Fig. 12 ): trochanter with transversal row of stout spines; outer margin of femur with few setae and spines, near ½ of dorsal surface with transversal row of bifid spines, inner margin with few stout spines, ¼ of dorsal surface with few long hairs; tibia with 3 bifid spines at mesal margin, inner distal margin with long bipectinate setae; few long hairs on tibia; tarsi with row of stout spines on inner margin, mesal margin with bipectinate spine; few long hairs on tarsi; claw long, slender and slightly hooked. Middle leg ( Fig. 13 ): trochanter with two bifid spines; outer margin of femora with long spines, ½ of inner margin with stout spines and remainder with bifid spines, dorsal surface with sparse bifid spines; inner margin of tibia with row of stout spines; ½ of tarsi with short bipectinate setae at mesal margin, claw long, slender and slightly hooked. Hindleg ( Fig. 14 ): trochanter with bifid spine; inner and outer margin of femur with long spines, ½ of dorsal surface with few bifid spines; inner margin of tibia with row of stout spines, outer margin with thin setae; tarsi similar to midleg; claw ( Fig. 15 ) long, slender and hooked with row of denticles. Abdomen. Terga VII–X yellowish brown; tergum II with pointed medial projection and pointed teeth on the posterior margin; posterior margin of terga VII–IX with row of long setae; abdominal sterna III–IX pale brown. Gills ( Figs. 16–19 ): pale brown; gill I ( Fig. 16 ) 2-segmented, distal segment 4 times longer than proximal segment; gill II ( Fig. 17 ) brown, covered with scales; margins evenly covered with long setae, inner margin with row of fringed setae; gills 3–6 ( Figs. 18 , 19 ) roughly triangular and with more than 15 multifid fimbriae with more than 2 branches; pigmented areas of the gill surface alternating with non-pigmented transparent tracheae. Cerci pale brown with whorls of setae in each segment.

Male Imago (in alcohol) ( Figs. 2 , 20–27 ): body length, 2.2–2.5 mm; cerci length, 8.8–9.1 mm; terminal filament, 9.6–9.9 mm; length of head 0.15 mm, width of head 0.5 mm; length of antenna 0.5 mm; length of forewing 1.85–2.05 mm; width of forewing 1.0– 1.3 mm; dorsal diameter of eye 0.1 mm; distance between compound eyes 0.125 mm; length of segments in foreleg femur/ tibia/ tarsus (mm): 0.45/0.9/0.6; length of tarsal segments 1 to 5 (mm): 0.03/0.28/0.12/0.11/0.06. Head ( Fig. 20 ) pale brown, anterior margin and area around antennal base pale brown; scape and pedicel of antennae pale brown, flagellum translucent. Thorax yellowish brown; prosternal triangle with slightly concave sides, tip acutely pointed ( Fig. 21 ). Legs: foreleg ( Fig. 23–25 ) pale brown, middle and hindleg translucent; fore femur brown, tibia washed brown and two times longer than femur; tarsomere I extremely short; tarsomere II apically with tongue-shaped projections on single side; tarsomeres II–IV provided with short spines ( Figs. 24–25 ); segment V short. Wings: Forewings ( Fig. 22 ) oval, with few cross veins; cross veins arranged singly except in R 1 and R 4; two cross veins at near ½ of R; MP forked at near 1/3 from base; CuA not forked. Veins C and Sc brown basally and washed brown distally, remaining veins translucent.Abdomen: tergum I–VI pale brown remaining terga translucent; sterna whitish. Genitalia ( Fig. 26 ) pale brown, penis lobes completely fused and produced laterally; styliger sclerite broad with short apophyses; forceps slender, apical part narrowed to the tip, with a long apical spine, and many trichomes on surface ( Fig. 27 ); cerci and terminal filament translucent with whorls of setae in each segment.

Female Imago (in alcohol) ( Figs. 3 , 28–30 ): body length, 4.3–4.6 mm; cerci length, 3.2–3.5 mm; terminal filament, 4.0– 4.3 mm; length of head, 0.3 mm, width of head, 0.8 mm; length of antenna, 0.6 mm; length of forewing, 3.2–3.5 mm; width of forewing, 1.4–1.7 mm; distance between compound eyes, 0.58 mm; dorsal diameter of eye, 0.12 mm; length of segments in foreleg femur/tibia/tarsus (mm): 0.52/0.73/0.63; length of tarsal segments (mm): 0.035/0.35/0.12/0.15/0.075. Head ( Fig. 28 ) pale brown; anterior margin and area around antennal base pale brown; scape and pedicel of antennae pale brown, flagellum translucent. Thorax yellowish brown; prosternal triangle with concave sides, tip acutely pointed ( Fig. 29 ). Legs: foreleg pale brown remainders translucent; tarsomere II much longer than others. Wings: veins C and Sc brown basally and washed brown distally, remaining veins translucent. Abdomen: terga I–VI pale brown remaining terga translucent; sterna whitish; cerci and median terminal filament translucent; posterior margin of sternum IX truncated ( Fig. 30 ).

Etymology. The species name maduraiensis refers to the locality, Madurai, Tamil Nadu where the new species was collected.

Figures

FIGURES 1–4. Caenis maduraiensis sp. nov. dorsal habitus: 1, Mature nymph; 2, Male imago; 3, Female imago; 4, Collection site.

FIGURES 5–11. Caenis maduraiensis sp. nov. mature nymph dorsal view: 5, Labrum; 6–7, Mandibles; 8–9, Maxillae; 10, Hypopharynx; 11, Labium.

FIGURES 12–18. Caenis maduraiensis sp. nov. mature nymph all drawings in dorsal view: 12, Foreleg; 13, Midleg; 14, Hindleg; 15, Hind tarsal claw; 16, Gill I; 17, Gill II; 18, Gill III.

FIGURES 19–30. Caenis maduraiensis sp. nov. Mature nymph: 19, Gill VI. Male imago: 20, Head; 21, Prosternal triangle; 22, Forewing; 23, Foreleg; 24, Tarsomeres II–III; 25, Foretarsus detail, 26, Genitalia, 27, Forceps detail. Female imago: 28, Head; 29, Prosternal triangle; 30, subanal plate.