Caenis venkataramani Srinivasan & Sivaruban & Barathy & Isack 2023, sp. n.
Creators: name: Srinivasan, Pandiarajan
name: Sivaruban, T.
name: Barathy, S.
name: Isack, Rajasekaran
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Ephemeroptera
Caenidae
Caenis
Caenis venkataramani

description: Caenis venkataramani sp. n.
(Figs. 58–99)
Materials examined. Holotype. L-S-IJ, South India, Tamil Nadu, Madurai District, Vaigai river, 10°08′86′′N, 77°85′28′′E, 204 m, 24.IX.2020, colls. P. Srinivasan & R. Isack (Reg. No. ZSI – SRC /I/E/743). Paratypes. 1 L-S-I ♀ (Reg. No. ZSI – SRC /I/E/744), 2 L-S-IJ, 1 L-S-I ♀, 5 larvae (AMC / ZN /201), South India, Tamil Nadu, Madurai District, Vaigai river, 9°95′52′′N, 78°06′59′′E, 144 m, 13.VI.2021, colls. P. Srinivasan & R. Isack. 2 L-S-IJ, Tamil Nadu, Madurai District, Karuppaurani lake, 9°94′07′′N, 78°18′84′′E, 132 m, 24.V.2020, colls. P. Srinivasan & R. Isack. 1 L-S-I ♀, South India, Tamil Nadu, Madurai District, Vaigai river, 9°95′52 ′′N, 78°06′59′′E, 192 m, 16.VI.2021, colls. P. Srinivasan & R. Isack (AMC /ZN/202).
Diagnosis. Caenis venkataramani sp. n. can be distinguished from all other Caenis species by the following combination of characters: Imago: 1) terga I–VI whitish with transverse black tinges (Fig. 60); 2) scutellum pale (Fig. 59); 3) base of antennal flagellum not dilated; 4) prosternal sclerite bell-shaped (Fig. 62); 5) foretarsus segments 2–4 each with a small tongue-shaped apico-median projection (Fig. 64); 6) penis narrow, more or less heart shaped, medio-laterally with short rounded lobes, hind margin with a well-developed medial incision; (Fig. 66) 7) basal half of forceps broad, abruptly narrowed in the apical part, apically with a long spine (Fig. 67). Larva: 1) genae distinctly bulged; 2) mesonotum with margins denticulate with slight bulging (Fig. 79); 3) forefemur with a transverse row of 6–7 strongly developed spatulate setae (Fig. 82); 4) hindclaw strongly bent with 3 very small basal denticles and a row of microdenticles (Fig. 91); 5) tergalius II with Y-shaped ridges poorly developed, inner one posteriorly reduced (Fig. 92); 6) hind margin of sternum IX broadly or triangularly rounded (Fig. 96); 7) shagreen on dorsal side of sternum IX with 8–9 irregular rows of very small denticles parallel to the hind margin. Egg: 1) two cap-like epithemata at the poles (Fig. 97); 2) chorionic surface smooth with transverse slender micropylar canal between polar caps (Fig. 98); 3) micropyle small with mouth not broadened (Fig. 99).
Description.
Male imago (Fig. 58). Measurements. Body length: 3.3 mm; forewing length: 2.1 mm; foreleg length: 2.1 mm; midleg length: 1.1 mm; hindleg length: 1.3 mm; cercus length: 7.8 mm. Ratios. Head (see Malzacher 2015; Fig. 4k): c: a = 2.3, a: b = 1; Leg: fore femur: fore tibia = 0.61; fore tibia: fore tarsus = 1.66; fore leg: hind leg = 1.6; segments of fore tarsus 1st: 2nd: 3rd: 4th: 5th = 1: 4.5: 3.1: 2.7: 1.4
Coloration. Head: Vertex with a dark brownish transverse band between lateral ocelli. Antenna: scape and pedicel pale. Thorax (Fig. 59): Pronotum with two black spots submedially and dark stripes laterally. Mesonotum dark brownish with stripes in the lateral areas; scutellum pale; mesonotal suture darkly pigmented; prosternum light brownish with dark stripes laterally, mesosternum, and metasternum light brownish, laterally with dark stripes. Wings hyaline, costa and subcostal veins reddish-brown. Legs whitish, except apical part of femora with a dark brownish patch; tibia dark brownish. Abdomen (Fig. 60): General coloration of terga whitish; terga I–VI whitish with transverse black tinges; terga VII–IX whitish with darkened lateral areas. Cerci translucent.
Head (Fig. 61). Fore margin between lateral and frontal ocelli straight. Pedicel two times the length of scape. Base of the antennal flagellum not dilated.
Thorax. Prosternal sclerites strong, forming an apically blunt or protruded isosceles triangle, without transverse strip (Figs. 62, 63). Foretarsus segments 2–4 each with a small tongue-shaped apico-median projection (Fig. 64) equipped with strong small spines (Fig. 65).
Abdomen. Tergum II without a finger-like process. Lateral filaments short. Genitalia and sternum IX as in Fig. 66. Penis narrow, more or less heart shaped, medio-laterally with short rounded lobes, hind margin with a well-developed medial incision (Fig. 67); styliger sclerite with very short apophyses. Basal half of forceps broad, abruptly narrowed in the apical part, apically with a long spine (Fig. 67).
Female imago (Fig. 68). Measurements. Body length: 5.3 mm; forewing length: 2.8 mm.
Coloration is similar to that of males. Terga I–VI transverse band strongly pronounced compared to that of males.
Mature larva (Fig. 69). Measurements. Body length (Fig. 13): 4.9–5.1 mm in female; 3.3–3.5 mm in male. Cerci length: 3.2–3.3 mm in female; 1.5–1.6 mm in male. Antennae length: 1.5–1.7 mm.
Head. Length 0.54 mm, width 0.82 mm. General coloration brown, vertex with a dark brownish transverse band between lateral ocelli. Hind margin without setae, antenna with fine, thin setae on each articulation. Pedicel two times the length of scape and with 3–4 simple setae on lateral margins (Fig. 71), genae distinctly bulged in lateral view. Mouthparts: Labrum (Fig. 72) twice as broad as long, medial emargination with thick setae, lateral margin with long simple setae, dorsal and ventral surface with scattered long, fine simple setae. Hypopharynx (Fig. 73) with minute hair-like setae on the apical margin and superlingua with long simple setae on the lateral margins. Right mandible. Outer incisor with three denticles and inner incisor with two denticles; medial margin with a small process between mola and incisors (Fig. 74). Left mandible. Outer incisor with five denticles; inner incisor with three denticles; medial margin without any process between mola and incisors (Fig. 75). The dorsal surface and outer margin of both mandibles scattered with a row of long, simple setae. Maxilla (Fig. 76). Three-segmented maxillary palp and with a ratio of 1: 0.6: 1; segment I with a row of five curved, spine-like setae on the outer margin; segment III with a longitudinal row of long simple setae near the inner marginal surface. Labium (Fig. 77). Glossa and paraglossa scattered with long, spine-like setae; three-segmented labial palp with length ratio of 1: 0.8: 0.6 (Fig. 77); segment I with a row of ten bipinnate bristles in the outer margin, segment II with long hair-like setae with 7–8 pectinate setae in the outer margin; surface with a bipinnate seta (Fig. 79), segment III with 6–8 spine-like setae in the inner margin and two transverse rows of long, spine-like setae on the apex along with scattered long hair-like setae on the surface and outer margin.
Thorax. Pronotum and mesonotum dark brownish and epidermal pigmentation similar to that of imago. Mesonotum with margins denticulate with slight bulging (Fig. 78). Legs: Cuticular coloration: Femora, tibiae and tarsi light brownish. Coxal processes nearly semi-circular with denticulate margins. Foreleg (Fig. 81): lengths of femur: tibia: tarsus: claw 0.55: 0.44: 0.32: 0.15 mm; femur with a transverse row of 6–7 strongly developed spatulate setae (Fig. 83) on ¾ of the distal region (Fig. 82); near the outer marginal surface a longitudinal row of spatulate setae present; distal outer margin consists of few spatulate setae; inner margin with row of long hair-like setae on the proximal half; tibia with longitudinal row of 4–5 spatulate setae on dorsal surface; outer margin with few hair-like setae; tarsi with longitudinal row of seven bipinnate bristles; outer and inner margins with few hair-like setae; claw slender without any denticulation (Fig. 80). Midleg (Fig. 84): lengths of femur: tibia: tarsus: claw 0.57: 0.36: 0.29: 0.15 mm. Femur with scattered spatulate bristles all over the surface; outer margin consists of a row of long spatulate setae; tibia with longitudinal row of 6–7 spatulate setae on dorsal surface; outer margin with row of short spine-like setae; tarsi with a longitudinal row of seven stout, bipinnate bristles, increasing in size distally; claw (Fig. 85) long, and curved without any denticles. Hindleg: lengths of femur: tibia: tarsus: claw 0.59: 0.47: 0.32: 0.15 mm. Femur (Fig. 86) similar to that of midleg; tibia (Fig. 87) with longitudinal row of 6–7 spatulate setae on dorsal surface (Fig. 88); outer margin with row of long spine-like setae; tarsi with a longitudinal row of seven stout, bipinnate bristles, increasing in size distally near the inner margin and a longitudinal row of spine-like setae on the inner margin (Fig. 89); claw strongly bent with three very small basal denticles (Fig. 91), and a row of microdenticles (Fig. 90).
Abdomen. All terga nearly light brownish. Tergalius II with diffuse light and dark brown areas without any shading medially and with dark brown patches on the other regions (Fig. 92). Tergalius II about twice the length of tergalius I. Tergum I lack posteromedian process; tergum II with a broadly blunt triangular posteromedian process with denticulate hind margin; Tergalius II with Y-shaped ridges poorly developed, inner ridge posteriorly reduced (Fig. 92); dorsal surface with numerous scales and 3–4 spatulate setae on the 1/3 rd half of Y-shaped ridge; left margin of Y-shaped ridge with a row of long simple setae with few small spatulate setae. Right margin of Y-shaped ridge with a row of small simple setae. Ventral row of microtrichia originates at anterior 1/5 th length of the tergalius II and ends in the posteromedial region; microtrichia elongated, more or less parallel-sided, and pinnate (Fig. 93). Tergalius III–VI with numerous filaments (Fig. 94). Posterolateral processes on tergum I absent; terga II–III with slightly marked posterolateral processes; terga IV–IX with well-developed posterolateral processes. Hind margins of tergum VII with long hair-like setae and tergum VIII with few long hair-like setae (Fig. 95) and terga IX and X with small denticles. Hind margin of sternum IX broadly or triangularly rounded (Fig. 96), shagreen on dorsal side of sternum IX with 8–9 irregular rows of very small denticles parallel to the hind margin. Cerci translucent.
Egg. Length: 110–115 μm; width: 70–75 μm; oval (Fig. 97); two cap-like epithema at the poles (Fig. 97); chorionic surface smooth with transverse slender micropylar canal between polar caps (Fig. 98), micropyle small, situated at the subequatorial plane with mouth not broadened (Fig. 99).
Etymology. This new species is named in honour of Dr. K. Venkataraman (mentor for the authors T. Sivaruban and S. Barathy) for his remarkable contribution to the Indian Ephemeroptera.
Distribution. Vaigai river, Madurai, Tamil Nadu, India.
Ecology. Larvae of Caenis venkataramani sp. n. were collected in the water temperature ranges between 24°C– 26°C; pH 7.2–7.3. Substratum is mainly made of cobbles and pebbles. The larvae of the Caenis venkataramani sp. n. shared their habitat with the larvae of Choroterpes (Euthraulus) latus (Leptophlebiidae), Tenuibaetis sp. (Baetidae), Labiobaetis operosus (Baetidae), Nigrobaetis klugei (Baetidae), Cheleocloeon vaigaiensis (Baetidae), Tricorythus meenakshi (Tricorythidae), Caenis maduraiensis (Caenidae) and Clypeocaenis kaveri (Caenidae).
Discussion. The male imago of Caenis venkataramani sp. n. is distinguished from other Oriental species of Caenis, except C. maratha by the shape of forceps, in which the basal part is very broad and the apical part is abruptly narrowed. It is distinguished from C. maratha by a well-developed medial incision in the hind margin of the penis. The larva of Caenis venkataramani sp. n. closely resembles that C. maduraienis and C. nigropunctatula. However, it is distinguished from C. maduraienis and C. nigropunctatula by the denticulation of the hind claw and by the mesonotal bulging in the larva and by the shape of the forceps in the imago.
description: Published as part of Srinivasan, Pandiarajan, Sivaruban, T., Barathy, S. & Isack, Rajasekaran, 2023, Contribution to the knowledge of family Caenidae (Insecta: Ephemeroptera) from Madurai District, Tamil Nadu, pp. 39-75 in Zootaxa 5258 (1) on pages 52-58, DOI: 10.11646/zootaxa.5258.1.2, http://zenodo.org/record/7773275