Caenis kaegies, Srinivasan & Sivaruban & Barathy & Isack, 2023

Srinivasan, Pandiarajan, Sivaruban, T., Barathy, S. & Isack, Rajasekaran, 2023, Contribution to the knowledge of family Caenidae (Insecta: Ephemeroptera) from Madurai District, Tamil Nadu, Zootaxa 5258 (1), pp. 39-75 : 44-52

publication ID	https://doi.org/ 10.11646/zootaxa.5258.1.2
publication LSID	lsid:zoobank.org:pub:D5B78BB6-E7AB-4CB8-B202-AA617E06F915
DOI	https://doi.org/10.5281/zenodo.7775624
persistent identifier	https://treatment.plazi.org/id/03C41A4F-5D19-602E-2A80-4110CBBE29D6
treatment provided by	Plazi
scientific name	Caenis kaegies
status	sp. nov.

Treatment

Caenis kaegies sp. n.

( Figs. 20–57 View FIGURES 20–23 View FIGURES 24–27 View FIGURES 28–30 View FIGURES 31–34 View FIGURES 35–37 View FIGURES 38–41 View FIGURES 42–44 View FIGURES 45–47 View FIGURES 48–53 View FIGURES 54–57 )

Materials examined. Holotype. L-S-IJ, 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/253) GoogleMaps . Paratypes. 1 L-SJ, 2 L-S-I ♀, 2 larvae ( AMC /ZN/254), 1 larva (Reg. No. ZSI –SRC/I/E/742) with same label data as holotype .

Diagnosis. Caenis kaegies sp. n. can be distinguished from all other Caenis species by the following combination of characters: Imago: 1) terga I–VI with more or less intense blackish transverse bands ( Fig. 22 View FIGURES 20–23 ); 2) scutellum darkly pigmented with anvil-shaped marking ( Fig. 28 View FIGURES 28–30 ); 3) base of antennal flagellum not dilated ( Fig. 23 View FIGURES 20–23 ); 4) prosternal sclerites bell-shaped ( Fig. 24 View FIGURES 24–27 ); 5) foretarsus segments 2–4 each with a small tongue-shaped apico-median projection ( Fig. 25 View FIGURES 24–27 ); 6) penis broad, with short rounded lobes ( Fig. 26 View FIGURES 24–27 ); 7) forceps short, basally broadened, consisting of a strong spine with blunt apex equipped with apical tuft of long spines ( Fig. 27 View FIGURES 24–27 ). Larva: 1) genae distinctly bulged; 2) pronotum and mesonotum denticulate without any bulging margins; 3) forefemur with a transverse row of 7–8 strongly developed spatulate setae ( Fig. 39 View FIGURES 38–41 ); 4) hindclaw with 3–4 basal denticles increasing in size distally, and a row of microdenticles, decreasing in size towards the distal end ( Fig. 47 View FIGURES 45–47 ); 6) dorsal surface of tergalius II with numerous scales and 4–5 spatulate setae on the 2/3 rd half of Y-shaped ridge ( Fig. 49 View FIGURES 48–53 ); 7) hind margin of sternum IX rounded with numerous minute indentations medially ( Fig. 52 View FIGURES 48–53 ). Egg: 1) chorion finely pored with a cap-like epithema ( Fig. 55 View FIGURES 54–57 ); 2) micropyle with mouth not broadened ( Fig. 56 View FIGURES 54–57 ).

Description.

Male imago ( Fig. 20 View FIGURES 20–23 ). Measurements. Body length: 1.8 mm; forewing length: 1.3 mm; foreleg length: 1.7 mm; midleg length: 0.7 mm; hindleg length: 0.8 mm; cercus length: 4.8 mm. Ratios. Head (see Malzacher 2015; Fig. 4k View FIGURES 4–7 ): c: a = 2.3, a: b = 1.1; Leg: fore femur: fore tibia = 0.51; fore tibia: fore tarsus = 1.42; fore leg: hind leg = 2.10; segments of fore tarsus 1st: 2nd: 3rd: 4th: 5th = 1: 4.6: 2.4: 1.9: 1.

Coloration. Head:Vertex with two more or less intense dark brownish transverse bands ( Fig. 23 View FIGURES 20–23 ).Antenna: scape and pedicel pale. Thorax: Prothorax dark brownish stripes medially and laterally, posterior margin of pronotum with dark brownish transverse band. Mesonotum generally pale with two black longitudinal bands in the sub medial area; scutellum darkly pigmented with anvil-shaped marking ( Fig. 21 View FIGURES 20–23 ); mesonotal suture darkly pigmented; prosternum, mesosternum, and metasternum pale yellowish. Wings hyaline, costa, and subcostal veins reddish-brown. Legs whitish, except apical part of femora and tibiae with a dark brownish patch. Abdomen: Terga I–VI with more or less intense blackish transverse bands, terga VII–IX ( Fig. 22 View FIGURES 20–23 ) mostly colourless medially and laterally with intense blackish stripes, tergum X mostly colourless. Cerci translucent.

Head ( Fig. 23 View FIGURES 20–23 ). Fore margin between lateral and frontal ocelli slightly bowed. Pedicel 2.5 times the length of scape. Base of the antennal flagellum not dilated.

Thorax. Prosternal sclerites forming a bell-shape; base of the triangle washed with dark brownish pigmentation ( Fig. 24 View FIGURES 24–27 ). Foretarsus segments 2–4 with a small tongue-shaped apico-median projection ( Fig. 25 View FIGURES 24–27 ) equipped with strong small spines.

Abdomen. Tergum II without a finger-like process. Lateral filaments short. Genitalia and sternum IX as in Fig. 26 View FIGURES 24–27 . Penis broad, with short rounded lobes, hind margin with a well-developed medial incision. Styliger sclerite broad with very short apophyses. Forceps longer than penis lobe, basally broadened, consisting of a strong spine with blunt apex equipped with apical tuft of long spines ( Fig. 27 View FIGURES 24–27 ).

Female imago ( Fig. 28 View FIGURES 28–30 ). Measurements. Body length: 3.8 mm; forewing length: 2.6 mm. Coloration similar to that of males. Terga I–VI with blackish transverse band strongly pronounced compared to that of males.

Mature larva ( Fig. 29 View FIGURES 28–30 ). Measurements. Body length: 3.4–3.5 mm in female; 2.5–2.7 mm in male. Cerci length: 1.7–2 mm in female; 1.2–1.4 mm in male. Antennae length: 0.8–1 mm.

Head. Length 0.40 mm, width 0.67 mm. General coloration brown, with a dark brownish transverse band between lateral ocelli; vertex dark brown with branch-like markings ( Fig. 29 View FIGURES 28–30 ). Hind margin without setae, antenna with thin setae on each articulation. Pedicel 1.5 times longer than scape and with 3–4 simple setae on lateral margins, genae distinctly bulged in lateral view. Mouthparts: Labrum ( Fig. 31 View FIGURES 31–34 ) 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 with minute hair-like setae on the apical margin and superlingua with long simple setae on the lateral margins. Left mandible. Outer incisor with four denticles; inner incisor with two denticles; medial margin without any process between mola and incisors ( Fig. 32 View FIGURES 31–34 ). Right mandible. Both outer and inner incisors with two denticles; medial margin with a small process between mola and incisors ( Fig. 33 View FIGURES 31–34 ). Dorsal surface and outer margin of both mandibles scattered with a row of long, strongly spatulate setae ( Fig. 34 View FIGURES 31–34 ). Maxilla ( Fig. 35 View FIGURES 35–37 ). Threesegmented maxillary palp; length ratio of palp segments 1: 0.6: 0.9; segment I with a row of five bipinnate bristles on the outer margin ( Fig. 36 View FIGURES 35–37 ); segment III with a longitudinal row of long simple setae the inner margin. Labium. Glossa with few small spines laterally; paraglossa with scattered long, spine-like setae ( Fig. 37 View FIGURES 35–37 ); three-segmented labial palp with length ratio of 1: 0.9: 0.5 ( Fig. 37 View FIGURES 35–37 ); segment I with a row of seven bipinnate bristles in the outer margin, segment II with long hair-like setae all over the surface and in the outer margin; outer marginal surface with a row of 5–7 pectinate setae, segment III with 6–8 spine-like setae on 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; epidermal pigmentation similar to that of imago ( Fig. 30 View FIGURES 28–30 ). Mesonotum with denticulate margins without any bulging. Legs. Cuticular coloration: Femora light brownish with diffuse light and dark areas; tibiae and tarsi light brownish. Coxal processes nearly semi-circular with denticulate margins. Foreleg ( Fig. 38 View FIGURES 38–41 ): lengths of femur: tibia: tarsus: claw 0.38: 0.28: 0.23: 0.14 mm; femur with a transverse row of 7–8 strongly developed spatulate setae on ¾ of the distal region ( Fig. 39 View FIGURES 38–41 ); proximal 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 5–6 spatulate setae on dorsal surface; outer margin with few hair-like setae ( Fig. 40 View FIGURES 38–41 ); tarsi with longitudinal row of two bipinnate bristles on the distal end; outer and inner margins with few hair-like setae; claw slender with four minute basal denticles ( Fig. 41 View FIGURES 38–41 ). Midleg ( Fig. 42 View FIGURES 42–44 ): lengths of femur: tibia: tarsus: claw 0.36: 0.22: 0.21: 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 5–6 spatulate setae on dorsal surface ( Fig. 43 View FIGURES 42–44 ); outer margin with row of short spine-like setae; tarsi with a longitudinal row of six stout, bipinnate bristles of variable in size; claw ( Fig. 44 View FIGURES 42–44 ) long, broad, and curved with six basal denticles. Hindleg ( Fig. 45 View FIGURES 45–47 ): lengths of femur: tibia: tarsus: claw 0. 40: 0.31: 0.19: 0.15 mm. Femur similar to that of midleg; tibia with longitudinal row of 5–6 spatulate setae on dorsal surface; outer margin with row of long spine-like setae; tarsi similar to that of midleg ( Fig. 46 View FIGURES 45–47 ); claw strongly curved with 3–4 basal denticles increasing in size distally, and a row of microdenticles, decreasing in size towards the distal end ( Fig. 47 View FIGURES 45–47 ).

Abdomen. Terga I, VII, and VIII dark brown; terga IX and X light brown; others whitish and laterally translucent. Tergalius II with diffuse light and dark brown areas without any shading medially and remaining areas with dark brown patches ( Fig. 49 View FIGURES 48–53 ). Tergalius II about twice the length of tergalius I. Tergum I without posteromedian process; tergum II with a broadly blunt triangular posteromedian process and denticulate hind margin ( Fig. 48 View FIGURES 48–53 ); tergalius II with Y-shaped ridges poorly developed, inner ridge posteriorly reduced ( Fig. 49 View FIGURES 48–53 ); dorsal surface with numerous scales and 4–5 spatulate setae on the anterior 2/3 rd half of Y-shaped ridge ( Fig. 49 View FIGURES 48–53 ); left margin of Y-shaped ridge with a row of long simple setae with few short 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. 50 View FIGURES 48–53 ). Tergalius III–VI with numerous filaments ( Fig. 51 View FIGURES 48–53 ). 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 long hair-like setae along with few spatulate setae and terga IX and X with small denticles. Hind margin of sternum IX rounded with numerous minute indentations medially ( Fig. 52 View FIGURES 48–53 ), shagreen on dorsal side of sternum IX with 8–9 irregular rows of very small denticles parallel to the hind margin ( Fig. 53 View FIGURES 48–53 ). Cerci translucent.

Egg. Length: 115–125 μm; width: 40–50 μm. Elongated ( Fig. 54 View FIGURES 54–57 ); chorion finely pored with a cap-like epithema ( Fig. 55 View FIGURES 54–57 ); micropyle small, situated at the subequatorial plane with mouth not broadened ( Fig. 56 View FIGURES 54–57 ), with visible circular sperm guide ( Fig. 57 View FIGURES 54–57 ).

Etymology. This species is named in honour of Dr. K.G. Sivaramakrishnan who is the mentor of the authors T. Sivaruban and S. Barathy, who has significantly contributed to the Indian Ephemeroptera . The species “ kaegies ” is an abbreviated patronym of Dr. K.G. Sivaramakrishnan, popularly known as “KGS” and hence the species name.

Distribution. Vaigai river, Madurai, Tamil Nadu, India.

Ecology. Larvae of Caenis kaegies sp. n. were collected in the riverine ecosystem with high amount of organic pollution, in which temperature ranges between 25°C–27°C; pH 7.3–7.4. Substratum is mainly made of cobbles and silt. The larvae of the Caenis kaegies sp. n. shared their ecological niche with the larvae of Cloeon sp. (Baetidae) and Caenis venkataramani sp. n. ( Caenidae ).

Discussion. Caenis kaegies sp. n. is distinguished from other Oriental species of Caenis by the darkly pigmented scutellum and bell-shaped prosternal triangle in imago. The larva of Caenis kaegies sp. n. closely resembles that of another Indian species, C. limai . However, it is distinguished from C. limai by the absence of bulging in the mesothorax and reduced number of spatulate setae in the transverse row of the forefemur.