Choroterpes (Dilatognathus) nicobarensis Selvakumar & Chandra

Selvakumar, C., Subramanian, K. A., Chandra, Kailash, Sivaramakrishnan, K. G., Jehamalar, E. Eyarin & Sinha, Bikramjit, 2017, A new species and a new record of the subgenus Dilatognathus Kluge 2012 (Ephemeroptera: Leptophlebiidae: genus Choroterpes Eaton, 1881) from India, Zootaxa 4268 (3), pp. 439-447 : 440-444

Choroterpes (Dilatognathus) nicobarensis Selvakumar & Chandra n. sp.

( Figs. 1–20 )

Material examined. Holotype: Ultimolarva, female, INDIA, Andaman and Nicobar Islands, Nicobar District , Great Nicobar Biosphere Reserve ( GNBR), East West Road , 16th km, Galathea tributary, 6.5889 N, 93.5186 E, 62 m, 4.iv.2012, coll. E. Eyarin Jehamalar (Reg. No. 5154/H13) . Paratypes: 2 penultimolarvae same data as holotype (Reg. No. 5155/H13); 1 pen-pen-penultimolarva, 1 pen-penultimolarva, 1 penultimatelarvae, 1 ultimolarva, all female, GNBR, East West Road, Govind Nagar , a stream on nature trail ½ km away from forest check post, 7.002 N, 93.5282 E, 106m, 10.xi.2010, coll. E. Eyarin Jehamalar (Reg. No. 5156/H13); 1 ultimolarva, female , GNBR, East West Road, Govind Nagar , 12th km, 7.001 N, 93.5287 E, 83 m, 06.xi.2010, coll. E. Eyarin Jehamalar (Reg. No. 5157/H13).

Description. Larva. Body length 3.5–4.0 mm, cerci 6 mm, median filament 7 mm ( Figs. 1–2 ). Labrum wide, median emargination shallow; proximal transverse row of setae interrupted medially; instead of distal transverse row, a wide stripe of irregular situated setae, smaller than setae of the proximal transverse row; closely set long setae laterally ( Fig. 5 ). Lingua of hypopharynx with well developed lateral processes, anterior margin shallowly cleft ( Fig. 6 ). Mandibles with outer margin moderately convex and with closely set long setae medially ( Figs. 7–8 ). Maxilla with inner-apical projection not stretched to a tusk-like process (in contrast to other Dilatognathus), with ventro-apical flange, with three pectinate setae and with pectinate dentiseta directed distally ( Figs. 9–11 ); structure of maxilla equal in ultimolarva and penultimolarva. Maxillary palp elongated and bears long filtering setae; 2nd segment in apical part of inner side with a few setae forming a longitudinal row; 3rd segment with a proximal semicircular transverse row of setae on inner side and fields of irregularly situated setae along with ventral and dorsal sides ( Figs. 9–11 ). Labium with paraglossae widened, expanded laterally; palp elongated and bears long filtering setae which form regular longitudinal rows; segment 2 with double row on outer side and a row on dorsal side; segment 3 with a row on outer side and a row on inner side; dorsal side of 3rd segment bears smaller irregularly situated setae ( Fig. 12 ).

Legs pale brownish. Femur of fore leg widest proximally, femora of middle and hind legs widest at middle. Femora with irregularly situated stout setae of various lengths, dorsal side of fore femur with few setae, dorsal side of middle and hind femur with many setae. Stout setae on inner side of fore tibiae situated densely and irregularly placed, pointed and bipectinate. Inner side of middle and hind tibia with a sparse row of stout setae ( Figs. 13–15 ). Claws apically hooked, with a row of subequal denticles ( Fig. 16 ). Hind wing pad present.

Posterolateral margins of abdominal terga with pointed denticles, size of denticles increases from tergum 6 to tergum 9 ( Figs. 1–2 ). Posterior margins of abdominal terga 1–2 with row of with very small, thin, spine-like denticles ( Fig. 3 ); terga 3–7 with row of small, thin, spine-like denticles ( Fig. 4 ); terga 8–9 with row of somewhat longer denticles; sterna lack denticles. Each abdominal tergum brown with lighter patches adjacent to anterior margin. Gill I absent; gills II–VII with dorsal and ventral lamellae terminated in 3 processes, with median process longer than laterals; gills II–V equal size, VI smaller, gill VII smallest ( Figs. 17–20 ). Terminal filament longer than cerci with a whorl of setae on alternate segments; setae shorter than length of corresponding segment.

Adult. Unknown.

Etymology. This species is named after the type locality, the Nicobar Islands.

Diagnosis. Choroterpes (Dilatognathus) nicobarensis n. sp. can be distinguished from all other species by the structure of the maxillary apex which lacks a tusk, with well-developed ventro-apical flange and dentiseta directed distally ( Figs. 9–11 ).

Figures

FIGURES 1 – 4. Choroterpes (D.) nicobarensis sp. n. 1. Dorsal view of female ultimolarva (holotype); 2. Dorsal view of female penultimolarva; 3. Abdominal tergum II; 4. Abdominal tergum VII.

FIGURES 5 – 12. Larva of Choroterpes (D.) nicobarensis sp. n. 5. Labrum; 6. Hypopharynx; 7. Left mandible; 8. Right mandible; 9 – 10. Maxilla of penultimolarva; 11. Apex of maxilla (ventral view; inner-apical projection, ventro-apical flange, dentiseta and pectinate ventral setae are shown, other setae not shown); 12. Labium.

FIGURES 13 – 20. Larva of Choroterpes (D.) nicobarensis sp. n. 13. Foreleg; 14. Midleg; 15. Hindleg; 16, Claw; 17. Gill II; 18. Gill IV; 19. Gill V; 20. Gill VII.