Chilikorchestia chiltoni Thacker & Myers & Trivedi & Mitra 2024, sp. nov.

Chilikorchestia chiltoni sp. nov.

(Figs. 2b & 6–8).

Material examined. Holotype male, 10.5 mm (LFSC.ZRC-201), Honeymoon Island, Chilika Lake (19°33'17"N 85°08'39"E), Odisha, India, 2 September, 2018, coll. D. Thacker. Paratypes, 1 male, 11 mm, 1 female, 4.5 mm (LFSC.ZRC-202), same data as holotype.

Etymology. The new species is named in honor of Charles Chilton, who worked as a Professor of Zoology at Canterbury University College, New Zealand and made a significant contribution to crustacean taxonomy. Charles Chilton was also a first researcher to publish a paper on amphipod diversity of Chilika Lake.

Description. Based on holotype male (10.5 mm) and paratype female (4.5 mm).

Head. Eyes medium, round. Antenna 1 slightly extending the distal end of the antenna 2 article 4 (Fig. 6: A1). Antenna 2 less than half of the length of the whole body; peduncular articles moderately incrassate; peduncular article 5 1.6 x as long as article 4; article 5 with some small robust setae (Fig. 6: A2). Labrum distal margin rounded with a row of small setae (Fig. 6: Lb). Labium with distally setose rounded plates (Fig. 6: L). Mandible left lacina moblis 5 dentate (Fig. 6: Md). Maxilla 1 vestigial with only 1 article. outer plate with 8 dentate setae; inner plate with 2 plumose setae (Fig. 6: Mx1). Maxilla 2 inner plate with a plumose seta on anterodistal corner (Fig. 6: Mx2). Maxilliped palp article 2 distomedial lobe well-developed; article 4 reduced, button shaped (Fig. 6: Mxp).

Pereon. Gnathopod 1 subchelate; coxa triangular, narrowing distally; basis 1.2 x as long as carpus; ischium subquadrate; merus shorter than carpus; carpus and propodus lobate on the posterodistal corner, palm with 4 robust setae; dactylus simplidactylate, subequal to palm (Fig. 7: G1). Gnathopod 2 subchelate, gill lobate; coxa subquadrate, posterior margin with a central shelf, ventral margin with few small hairs on posterior half, ventral margin with irregularly placed small robust setae; basis twice as long as broad, posterior margin with 4 small robust setae; ischium small; carpus small subrectangular; propodus oval, palm transverse with several small robust setae and a long protuberance at the posterodistal corner; dactylus longer than palm, fits into the groove formed on the protuberance (Fig. 7: G2). Pereopod 3–7 bicuspidactylate (Figs. 7: P3–P7). Pereopod 3 coxa subquadrate; basis long with robust setae on both margins; merus 1.5 x as long as carpus; propodus subequal to carpus (Fig. 7: P3). Pereopod 4 smaller than pereopod 3; basis long with robust setae on both margins; merus 1.6 x as long as carpus; propodus 1.2 x as long as carpus (Fig. 7: P4). Pereopod 5 basis expanded; merus subequal to carpus; propodus 1.3 x as long as carpus (Fig. 7: P5). Pereopod 6–7 similar, except pereopod 6 basis oval were as pereopod 7 basis subquadrate (Figs. 7: P6 & P7).

Pleon. Uropod 1 peduncle longer than rami with 7 robust setae in two margins, distolateral robust setae present, small, with simple tip; exopodite subequal to endopodite, without marginal robust setae; endopodite with 3 robust setae on inner margin (Fig. 7: U1). Uropod 2 peduncle little longer than rami, with 5 robust marginal setae; endopodite subequal to exopodite, with 2 marginal setae on inner margin; exopodite with 4 robust setae in two margins (Fig. 8: U2). Uropod 3 uniramous; peduncle longer than ramus with 2 robust setae; ramus narrowing distally (Fig. 8: U3). Telson slightly longer than broad, apically notched, with 5–6 robust setae on each lobe (Fig. 8: T).

Female (sexually dimorphic characters). Gnathopod 1 parachelate; posterior margin of carpus and propodus without lobe; propodus subrectangular. Gnathopod 2 mitten-shaped.

Remarks. This is the first record of a member of the Plarorchestiinae occurring in India. Previous records of Platorchestia platensis (Krøyer, 1845) from India (Barnard, 1935, Dev Roy et al., 2009, Surya Rao, 1972, Thilagavathi et al., 2013) are erroneous.

Distribution. Currently known only from the type locality.