Tricorythus meenakshi, Srinivasan & Sivaruban & Barathy & Isack, 2022

Srinivasan, Pandiarajan, Sivaruban, T., Barathy, S. & Isack, Rajasekaran, 2022, The unexpected discovery of the Afrotropical genus Tricorythus Eaton, 1868 (Ephemeroptera: Tricorythidae) from the Oriental region with description of a new species, Zootaxa 5222 (4), pp. 343-359 : 344-358

Tricorythus meenakshi sp. n.

( Figs. 1–56 )

Materials Examined. Holotype (in slide): L-S-IJ, INDIA, Tamil Nadu state, Madurai, Vaigai River , 11.X.2022, coll. P. Srinivasan, R. Isack ( AMC /ZN/262) . Paratypes (in ethanol): the same locality and collectors, 31.VII.2022: 1 L-S-IJ, 20 larvae ( AMC /ZN/263) .

Diagnosis. The new species has a unique combination of characters: In male imago, i) body dorsally with a colorless median stripe from head to abdomen ( Fig. 1 ); ii) femur and base of the tibia of all legs washed with black or dark brown, other parts mostly colorless ( Figs. 5, 7–8 ); iii) penis smaller than gonostyli, narrow, and mostly parallel-sided, splits near the apex, with apices joined ( Fig. 11 ). In the larva, i) body slender ( Fig. 20 ); ii) entire body dark brown nearly unicolor, with a colorless median stripe from head to the end of abdomen ( Fig. 20 ); iii) protoptera dark in both sexes; iv) prostheca of left mandible asymmetrically or symmetrically widened apically, with 3–4 bristle-like processes at base ( Fig. 29 ); v) transverse row on ventral side of maxilla with 8–10 bristles ( Fig. 32 ); vi) pronotum of both sexes simple ( Figs. 22–23 ); vii) claws with a row of 3–5 denticles on the inner margin, 2–4 small denticles at the base, and a larger denticle close to it ( Figs. 37–39 , 47 ), two subapical denticles on ventral side and a subapical denticle present on dorsal side ( Figs. 47, 50 ); viii) denticles on hind margins of abdominal terga triangular, either pointed, or blunt, or terminated by several points ( Fig. 52 ).

Descriptions.

Imago, male. COLORATION: Entire body dark brown naturally (became light brown to yellow in alcohol) ( Fig. 1 ). Dorsally with colorless median stripe from head to abdomen ( Fig. 3 ). Head with yellowish to light brownish transverse band between lateral ocelli; prothorax with black longitudinal bands medially and sublaterally ( Fig. 2 ). Wings tinged light brown, more intensely in costal and subcostal areas ( Fig. 9 ). Legs. Femur washed with black or dark brown, base of tibia washed with black or dark brown, and other parts mostly colorless ( Figs. 5, 7& 8 ). Each abdominal tergum and sternum with dark brown longitudinal stripe in lateral areas ( Figs. 3, 4 ). Styliger dark brown; gonostyli and penis entirely lacking coloration. Caudalii dark brown in proximal half of segments and pale in distal half.

SHAPE: Eyes small ( Fig. 2 ). Mesonotum with strongly curved lateroparapsidal suture ( Fig. 16 ). Claws of foreleg blunt ( Fig. 6 ) and claws of other legs ephemeropteroid ( Figs. 7, 8 ). Genitals as in Figs 10–13 : Styliger short, with posterior margin either nearly straight ( Fig. 10 ) or shallowly convex. Papillae on posterior margin of styliger small spine-like and sparse ( Fig. 12 ). Penis non-sclerotized, smaller than gonostyli, narrow, and mostly parallel-sided, splits near apex, with apices joined ( Fig. 11 ). Papillae on second segment of gonostylus broad and mostly blunt at apex ( Fig. 13 ).

Subimago, male. COLORATION AND TEXTURE: Hypodermal pigmentation as in imago (see above). Cuticle of pronotum brown with composite branched blanks; densely covered with microtrichiae except in blanks. Mesonotum with antelateroparapsidal suture and anterolateral scutal costa dark brown; anteronotal protuberance, medioscutum, submedioscutum and sublateroscutum brown; most part of lateroscutum and posterior scutal protuberance colorless ( Fig. 16 ). Except in posterior scutal protuberances, other areas of mesonotum entirely covered with microtrichiae; posterior scutal protuberances covered with net-like relief ( Fig. 17 ). On each leg, cuticle of femur with dark brown longitudinal stripes ( Fig. 14 ); cuticle of tibia with proximal and distal ends and outer surface darkened, other parts colorless; tarsus segments I to III darkened and segment IV colorless. Tibia and tarsus of all legs covered with microtrichiae ( Fig. 15 ). Claws of all legs ephemeropteroid. Cuticle of abdominal terga dark brown, with a colorless median stripe and paired blanks ( Fig. 18 ), cuticle of abdominal sterna dark brown and with pair of blanks submedially and sublaterally; gonostyli pale, with contrasting dark brown band at joining of first and second segments ( Fig. 19 ). Cuticle of caudalii colorless.

Larva. COLORATION: Entire body dark brown nearly unicolor, with colorless median stripe from head to the end of abdomen ( Figs. 20, 21 ). Prothorax dark brown medially and colorless laterally ( Fig. 22 ); mesothorax with pair of colorless stripes laterally. Legs similar to that of imago, femur washed with black or dark brown, base of tibia washed with black or dark brown, other parts mostly colorless. Protoptera dark in both sexes. Tergalii with dorsal lobe colorless, ventral lobe gray. Caudalii mostly colorless. Cuticular coloration similar to that of hypodermal pigmentation ( Figs. 24, 25 ).

SHAPE: Head: Frons and clypeus without projections. Eyes of male as small as female ( Figs. 22–24 ). Labrum. Two times wider than long, dorsal surface entirely covered with scattered ribbon-like bristles and two lateral groups of bristles on ventral side ( Fig. 26 ). Hypopharyngeal lingua wider than long without any nick at anterior margin ( Fig. 27 ). Mandibles with incisors not elongated, curved ( Figs. 28, 30 ); left prostheca asymmetrically or symmetrically widened apically, with 3–4 bristle-like processes at base ( Fig. 29 ); shape of right prostheca similar to other Tricorythus ( Fig. 31 ). In last larval instar, transverse row on ventral side of maxilla with 8–10 bristles ( Fig. 32 ). Maxillary palp two-segmented, elongated and arched ( Fig. 32 ). Labium. Glossae and paraglossae fused into rounded triangular plate. Labial palps three-segmented, third segment much smaller than other two segments ( Fig. 33 ). Thorax: Pronotum moderately wide; anterolateral angles slightly projected forward; anterior margin between them in both sexes nearly straight or slightly convex ( Figs. 22–24 ); mesonotum not shortened. Femora narrow ( Figs. 34–36 ). Ratio of femur length: width = 2.9: 1 (Forefemur); 3.2: 1 (midfemur); 3.4: 1 (hindfemur). Length ratio of femur: tibia: tarsus = 1.6:2:1 (forelegs); 1.9: 2.2: 1 (midlegs); and 2.3:2.9:1 (hindlegs). Fore femur with irregular transverse row of spatulate setae ( Figs. 41 , 45 ), which are different in size; entire surface covered with long, apically blunt lanceolate setae, outer margin without any spatulate setae ( Fig. 40 ); Tibia of foreleg with three longitudinal rows of stout, spatulate setae; on dorsal surface, inner-dorsal marginal surface, and inner-ventral marginal surface ( Figs. 42 , 46 ). Inner margin of foretarsus with row of spine-like setae, increasing in size distally along with few hair-like setae ( Fig. 43 ). Foreclaw with a row of 3–5 denticles on the inner margin, 2–4 small denticles at the base, and a larger denticle close to it ( Figs. 37–39 , 47 ). Two subapical denticles on ventral side and subapical denticle on dorsal side ( Figs. 37 , 47 ). Mid and hind femora with longitudinal row of long, spatulate setae on distal half of outer margin ( Fig. 48 ); dorsal surface with few, irregularly arranged stout spatulate setae much smaller than spatulate setae on outer margin ( Fig. 49 ). Tibiae of mid and hind legs with longitudinal row of stout, spatulate setae on outerdorsal margin in addition to three longitudinal rows similar to that of foretibia ( Fig. 44 ). Tarsi and claws of mid and hind legs similar to foreleg ( Figs. 38, 39 , 50 ). Abdomen: Tergalii present on abdominal segments II–VI ( Fig. 25 ). Tergalius each with dorsal lamellate lobe and ventral bifurcate lobe with numerous lateral filaments ( Fig. 51 ). Vestiges of tergalii VII absent. Denticles on hind margins of abdominal terga triangular, either pointed, or blunt, or terminated by several points ( Fig. 52 ). Protopenis small, cleft up to middle, with paired lobes, not reaching posterior margin of genital plate ( Fig. 53 ).

Dimension. Body length and forewing length 4–5 mm.

Female alates. Unknown.

Egg (extracted from mature larva). Chorion with longitudinal relief structures stretching from polar cap to opposite pole and shorter structures of same kind ( Figs. 54, 55 ). Single polar cap covering approximately 1/3 of surface, bluntly pointed at apex ( Fig. 56 ).

Etymology. The species name “ meenakshi ” refers to the prestigious Meenakshi Amman temple which is the pride of Madurai city, where the new species was collected.

Distribution. Vaigai River (Madurai, Tamil Nadu).

Figures

FIGURES 1–4. Tricorythus meenakshi sp. n., male imago. 1, dorsal view (holotype); 2, head and thorax; 3, terga (holotype); 4, sterna (holotype).

FIGURES 5–9. Tricorythus meenakshi sp. n., male imago (holotype). 5, foreleg; 6, foretarsus; 7, midleg; 8, hindleg; 9, forewing.

FIGURES 10–13. Tricorythus meenakshi sp. n., genitalia of male imago (holotype). 10, dorsal view; 11, penis; 12, gonostylus segment I; 13, gonostylus segment II.

FIGURES 14–19. Tricorythus meenakshi sp. n., male subimaginal exuviae (holotype). 14, foreleg; 15, microtrichiae in the foretibia; 16, right half of mesonotum; 17, net-like relief in posterior scutal protuberances; 18, abdominal terga; 19, abdominal sterna.

FIGURES 20–23. Tricorythus meenakshi sp. n., larvae. 20, dorsal view of the female larva; 21, ventral view of the female larva; 22, head and pronotum of the female larva; 23, head and pronotum of the male larva.

FIGURES 24–27. Tricorythus meenakshi sp. n., larvae. 24, head and pronotum of the male larval exuviae (holotype); 25, abdomen of the male larval exuviae (holotype); 26, labrum; 27, hypopharyngeal lingua (holotype).

FIGURES 28–33. Tricorythus meenakshi sp. n., larvae. 28, left mandible; 29, prostheca of the left mandible; 30, right mandible; 31, prostheca of the right mandible; 32, maxilla (holotype); 33, left half of the labium (holotype).

FIGURES 34–39. Tricorythus meenakshi sp. n., legs of larval exuviae (holotype). 34, foreleg; 35, medleg; 36, hindleg; 37, foreclaw; 38, midclaw; 39, hindclaw.

FIGURES 40–44. Tricorythus meenakshi sp. n., legs of larval exuviae (holotype). 40, forefemur; 41, spatulate seta on the transverse row of the forefemur; 42, foretibia; 43, foretarsus; 44, midtibia.

FIGURES 45–50. Tricorythus meenakshi sp. n., SEM view of larval legs. 45, forefemur; 46, foretiba; 47, foreclaw; 48, midfemur; 49, spatulate setae on the surface of midfemur; 50, subapical denticles on the midclaw.

FIGURES 51–53. Tricorythus meenakshi sp. n., larval exuviae (holotype). 51, tergalius IV; 52, posterior margin of the tergum VII; 53, protopenis in sternum IX.

FIGURES 54–56. Tricorythus meenakshi sp. n., SEM view of eggs.