Sparsorythus sivaramakrishnani Sivaruban, Srinivasan, Barathy, Bernath

Srinivasan, Pandiarajan, Rosi, Bernath & Isack, Rajasekaran, 2021, A new species of Sparsorythus Sroka & Soldán, 2008 (Ephemeroptera: Tricorythidae) from Eastern Ghats of Southern India, Zootaxa 4915 (2), pp. 237-245 : 238-241

Sparsorythus sivaramakrishnani Sivaruban, Srinivasan, Barathy, Bernath rosi & Isack sp. nov.

Figs. 1–22 .

Materials Examined. Holotype (in alcohol): Female mature nymph ( AMC ZN 183 ), South India, Tamil Nadu, Namakkal district , Thuraiyur , Pullian cholai, 11.2668 N & 78.4361 E; 1190 m a.s.l; 11/I/2020, Bernath Rosi, Pandiarajan Srinivasan, Rajasekaran Isack . Paratypes: 1 male nymph ( AMC ZN 184 ) and 2 female nymphs ( AMC ZN 185 ) same data as holotype . Holotype and paratypes are deposited in the The American College museum, Madurai, Tamil Nadu, India .

Mature nymph (in alcohol): Male body length: 2.95–3.05 mm, Female body length: 3.55–3.80 mm ( Figs. 1, 2 ). Body colouration brownish yellow, ventral side of body pale creamy color.

Head: Head wider than long and dark blackish brown (ratio of length: width is 1:2.1). Head widths: 1.02 mm (male) and 1.25 mm (female). Antenna slightly longer than head length 1.8:1 (male) and 1.6:1 (female). Scapes about one half length of pedicels. Compound eyes black, ocelli greyish. Eyes of female slightly larger than male eyes. Ratio of distance between compound eyes to eye width of male = 3.1:1, female = 3.9:1. Labrum ( Fig. 3 ) oval, ratio of width: length 2.6:1; dorsal surface entirely covered with scattered bristles and tiny bristles on ventral side. Hypopharyngeal lingua wider than long divided by long rill in middle and nick at anterior margin of lingua ( Figs. 4, 5 ). Maxillae ( Fig. 6 ) oblong shaped, approximately 1/3 longer than wide, apical part truncate. Maxillary palps absent. Labium: Glossae and paraglossae fused into rounded triangular plate and with two groups of setae on lateral submargin. Labial palps three-segmented. First segment oblong shaped, about by 1/3 shorter than second one, without any setation. Second segment curved, apical end pointed bluntly with row of stout marginal setae at its outer margin and tiny submarginal setae at its inner margin. Third segment very small, bluntly pointed at apex, without any setation. Labial plate ( Figs. 7, 8 ) without small nick at middle of anterior margin. Mandibles ( Figs. 9–12 ) robust and each with row of long filtering setae on outer margin; outer incisor of both mandibles triangular, with numerous bristles on ventral side; apex with pair of rounded projections; ventral side of inner incisor with bristles and dorsal side with tiny branched setae; left prostheca ( Fig. 10 ) asymmetrically wider apically, with several pointed teeth and with three to four bristle-like processes at base; length of left prostheca subequal to length of inner incisor; right prostheca ( Fig. 12 ) notched, extended apically with several pointed teeth, no setae on inner side; length of right prostheca approximately 2/3 as long as inner incisor.

Thorax: Width of pronotum subequal to width of head; head about twice longer than wide. Posterior margin of mesonotum overlapping at segment V of female and segment VI of male. Length ratio of femur:tibia:tarsus = 1.8:2.3:1 (forelegs); 2.2:2.3:1 (midlegs); and 2.3:2.7:1 (hindlegs). Femora flat, shorter than tibiae. Hind legs larger than fore and midlegs ( Figs. 13–15 ). Transversal row of setae on the fore femora bow-shaped ( Fig. 16 ), with group of chaotically inserted setae near fore femoral posterior margin. Fore femoral setae about 4.5–5.5 times longer than wide with blunt apex ( Fig. 17 ). Setae on fore tibiae very thin, spiky and about 0.080 mm in size ( Fig. 18 ). Dorsal surface of middle and hind femora sparsely covered by spines of variable size ( Fig. 19 ). Mid and hind femora each with short setae at inner margin and long stout setae at outer margin, row of stout setae along outer margin of mid and hind femora irregular. Inner margin of mid and hind tibia with longitudinal row of stout setae and about 0.020 mm in size. Tarsal claws hooked, bearing 2 median denticles and two lateral subapical teeth.

Abdomen: Abdomen not flat, lateral sides on segments II–VII concave, segments VIII–IX cylindrical. Denticles of hind margin of abdominal tergum VII short, either pointed or blunt ( Fig. 20 ), or terminated by several points. Gills absent on abdominal segment I; gills present on abdominal segments II–VI. Gills each with dorsal lamella and ventral portion consisting of two branches with numerous lateral filaments ( Fig. 21 ). Gills absent from segment VII. Caudal filaments: cerci as long as paracercus. Sexual dimorphism: cerci and paracercus of males much wider and compressed at base than those of females ( Figs. 1, 2 ). Individual segments of caudal filaments each rounded at posterior margin with setae approximately as long as 1/4 of length of segment. Lateral margins with spiky setae as long as length of corresponding segments, with these setae present on both sides of paracercus and only on inner sides of cerci ( Fig. 22 ).

Etymology. This species is dedicated to our revered Mentor Dr. K.G. Sivaramakrishnan, for his outstanding contribution to the Indian Ephemeroptera .

Diagnosis. The diagnostic characters of Sparsorythus sivaramakrishnani sp. nov. are listed in Table 1, following Sroka and Soldán (2008).

Ecology. The nymphs of Sparsorythus sivaramakrishnani sp. nov. were collected in the stream of Pullian cholai, Thuraiyur, Namakkal district (8–10 m wide, 4.6–10.9 cm depth). The water current is about 1.12 m /sec. The water temperature ranges between 21°C–23°C and pH 7.1–7.4. Substratum is of high cobble and rocks, with high water velocity.

Figures

FIGURES 1–2. Nymph of Sparsorythus sivaramakrishnani sp. nov. 1—Male nymph 2—Female nymph

FIGURES 3–12. Mouthparts of Sparsorythus sivaramakrishnani sp. nov. 3—Labrum 4—Hypopharyngeal lingua 5—Medial nick on hypopharynx 6—Maxilla 7—Labium 8—Labium anterior without medial nick 9—SEM view of Left mandible 10—SEM view of Left prostheca 11—SEM view of Right mandible 12—SEM view of Right prostheca.

FIGURES 13–19. Nymph of Sparsorythus sivaramakrishnani sp. nov. 13 —Foreleg 14 —Midleg 15 —Hindleg 16 —SEM view of transverse setae on Forefemur 17 —SEM view of structure of transverse setae in Forefemur 18 —Bristle like Foretibial setae 19 —SEM view of different shaped setae in the surface Midfemur.

FIGURES 20–22. Nymph of Sparsorythus sivaramakrishnani sp. nov. 20—Hind margin of tergum VII 21—Gill II 22—Paracercus and Cercus.