Caenis maduraiensis Balasubramanian and Muthukatturaja, 2021

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 : 42-44

Caenis maduraiensis Balasubramanian and Muthukatturaja, 2021

( Figs. 8–19 )

Materials examined. Photos of paratype provided by Zoological Survey of India ( ZSI), Southern Regional Centre, Chennai, India. 2 L-S-IJ ( AMC /ZN/199), 2 L-S-I ♀ ( AMC /ZN/200), South India, Tamil Nadu, Madurai District, Vaigai river, 10°08′32′′N, 77°93′20′′E, 192 m; 3.X.2020, colls. P. Srinivasan & R. Isack .

Diagnosis. Caenis maduraiensis can be distinguished from all other Indian representatives of Caenis by the following combination of characters, in the imago: 1) base of antennal flagellum not dilated; 2) foremargin between lateral and frontal ocelli slightly bowed ( Fig. 9 ); 3) foretarsus segment 2 with an apico-median projection ( Muthukatturaja and Balasubramanian 2021; Fig. 24 ); 3) penis broad, with rounded lobes of moderate length ( Fig. 10 ); 4) forceps marginally narrowed to the tip, with a short spine bent medially and basally with a small rounded bulging in the outer margin ( Fig. 10 ). Larva: 1) cuticle of femora of all legs light brownish-ochre, with diffuse light and darker areas; tibiae and tarsi light brownish-ochre ( Fig. 11 ); 2) forefemur with a transverse row of 6–7 strongly developed spatulate setae on ¾ of distal region ( Fig. 11 ); 3) proximal inner margin of forefemur with a row of long hair-like bristles ( Fig. 11 ); 4) hindclaw with a row of very fine microdenticles ( Fig. 13 ); 5) hind margin of sternum IX posteriorly protruding and triangular rounded on the apex ( Fig. 14 ). Egg: 1) chorion strongly pored with two epithemata of coiled-rope-type with numerous small terminal knobs, located at the poles ( Fig. 18 ); 2) micropyle short and triangular.

Additions to the description. Detailed descriptions of the imago and larva of Caenis maduraiensis are given by Muthukatturaja and Balasubramanian (2021). However, several important diagnostic characters of the imago and larva were not described in the original description.

Male imago ( Fig. 8 ). Foremargin between lateral and frontal ocelli slightly bowed ( Fig. 9 ). Forceps marginally narrowed to the tip, with a short spine bent medially and basally with a small rounded bulging in the outer margin ( Fig. 10 ).

Larva. Legs. Cuticular coloration: Femora of all legs light brownish-ochre, with diffuse light and darker areas; tibiae and tarsi light brownish-ochre. Foreleg. Femur with a transverse row of 6–7 strongly developed spatulate setae on ¾ of distal region ( Fig. 11 ), row of long hair-like bristles present on 1/3 of the proximal inner margin. Hindleg. Dorsal surface of femur with only a few spatulate setae on the proximal half ( Fig. 12 ). Claw with a row of very fine microdenticles, subequal in size ( Fig. 13 ). Abdomen. Hind margin of sternum IX posteriorly protruding, triangular, rounded on the apex ( Fig. 14 ); shagreen on dorsal side of sternum IX with 6–7 irregular rows of very small denticles parallel to the hind margin ( Fig. 15 ).

Egg. Length: 105–110 μm; width: 45–55 μm. Elongated ( Fig. 16 ); chorion strongly pored ( Fig. 18 ) with two epithemata of coiled-rope-type with numerous small terminal knobs, located at the poles ( Fig. 18 ). Epithemata of a modified C. perpusilla subtype ( Fig. 17 ). Micropyle short and triangular.

Discussion. Formerly Srinivasan et al. (2021a), misidentified specimens of C. maduraiensis as Caenis nigropunctatula based on the similar kind of genitalia of the male imago. However, C. maduraiensis can be distinguished from C. nigropunctatula by, in imago, i) bowed foremargin between lateral and frontal ocelli, whereas, in C. nigropunctatula , fore margin between lateral and frontal ocelli straight ( Malzacher 2015; Fig. 4l ); ii) basal part of the forceps with a small rounded bulging in the outer margin, whereas, in C. nigropunctatula , no bulging in the basal part of the forceps ( Malzacher 2015; Fig. 1c–i ). In larva, i) dorsal surface of forefemur with a transverse row of 6–7 strongly developed spatulate setae on ¾ of distal region, whereas, in C. nigropuctatula , no transverse row in the dorsal surface of forefemur ( Malzacher, 2015); ii) foreclaw without any denticulation, whereas, in C. nigropunctatula , foreclaw with a row of strong denticles ( Malzacher 2015; 2d); iii) shagreen on dorsal side of sternum IX with 6–7 irregular rows of very small denticles parallel to the hind margin, whereas, in C. nigropunctatula , no shagreen field present on the sternum IX ( Malzacher, 2015).

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

Ecology. Larvae of Caenis maduraiensis 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 Caenis maduraiensis shared habitat with Choroterpes (Euthraulus) latus (Leptophlebiidae) , Tenuibaetis sp. (Baetidae) , Labiobaetis operosus (Baetidae) , Nigrobaetis klugei (Baetidae) , Tricorythus meenakshi (Tricorythidae) , Caenis venkataramani sp. n. ( Caenidae ) and Clypeocaenis kaveri (Caenidae) .

Figures

FIGURES 8–15. Caenis maduraiensis Balasubramanian and Muthukatturaja, 2021: (8) male imago (holotype); (9) head of male imago; (10) forceps; (11) forefemur of larval exuvia; (12) hindfemur of larval exuvia; (13) hindclaw; (14) sternum IX of male larval exuvia; (15) shagreen field in the dorsal surface of sternum IX.

FIGURES 16–19. SEM view of eggs of Caenis maduraiensis Balasubramanian and Muthukatturaja, 2021: (16, 17) entire view; (18) epithemata; (19) closer view of chorion.

FIGURES 24–27. Male imago of Caenis kaegies sp. n.: (24) prosternal triangle; (25) foretarsus; (26) male genitalia; (27) forceps.

FIGURES 4–7. SEM view of eggs of Caenis americani Srinivasan et al. 2021: (4) entire view; (5) epithemata; (6) closer view of chorion; (7) micropyle.

FIGURES 1–3. Caenis americani Srinivasan et al. 2021: (1) female imago; (2) head and thorax of larval exuvia (arrows indicate bulging in mesonotum); (3) hindleg of larval exuvia.