Grandidierella rabindranathi, Thacker & Myers & Trivedi & Mitra, 2024

Thacker, Dimple, Myers, Alan A., Trivedi, Jigneshkumar N. & Mitra, Santanu, 2024, On a small collection of amphipods (Crustacea, Amphipoda) from Chilika Lake with the description of three new species and a new genus, Zootaxa 5446 (3), pp. 383-404 : 394-398

Grandidierella rabindranathi sp. nov.

( Figs. 2c , 9–11 )

Material examined. Holotype male, 6.5 mm ( LFSC.ZRC-203), Barkuda Island , Chilika Lake (19°33'12"N 85°08'07"E), Odisha, India, 2 September, 2018, coll. D. Thacker. Paratypes, 1 male, 6 mm ( LFSC.ZRC-204) , 1 female, 5.5 mm ( LFSC.ZRC-204), same data as holotype .

Etymology. The new species is named in honor of Dr. P. Rabindranath, who worked as a professor at Department of Zoology, N.S. S. College, Changanacherry, Kerala, India and made a significant contribution to Amphipod taxonomy.

Diagnosis.

Male Gnathopod 1 carpus anterior margin with few setae, posterodistal spine present; propodus oval with posterior margin convex. Gnathopod 2 coxa ventral margin without spine; basis 3.4 x as long as broad.

Female gnathopod 1 carpus 0.89 x as long as propodus, propodus subrectangular, dactylus inner margin serrated. Gnathopod 2 carpus 1.21 x as long as propodus, dactylus inner margin weakly serrated.

Description. Based on holotype male (6.5 mm) and paratype female (5.5 mm).

Head. Eyes of moderate size, round. Antenna 1 slender, about 0.85 x as long as body; length ratio of peduncular articles 1–3 1:1.58:0.54; primary flagellum 1.4 x as long as peduncle; accessory flagellum minute, one articulated ( Fig. 9 : A1). Antenna 2 stout 0.65 x as long as body; length ratio of peduncular articles 3–5 1:3:2.96; flagellum short with 6 normal and 1 minute article ( Fig. 9 : A2). Mandible palp articles 1–3 ration 1:1.59:1.44, article 3 subrectangular ( Fig. 9 : Md). Maxilla 1 outer plate with 10 epical robust setae, palp article 2 with 5 apical robust setae ( Fig. 9 : Mx1). Maxilla 2 inner plate with epical and marginal setae and a mediofacial row of setae, outer plate epically setose ( Fig. 9 : Mx2). Maxilliped inner plate setose; outer plate with 7 robust marginal setae; palp 3 articulated, article 1 with seta on inner margin; article 2–3 with setae on both margins ( Fig. 9 : Mxp).

Pereon. Gnathopod 1 coxa subrectangular; basis 2.9 x as long as broad with weakly setose posterior margin; ischium broader than long, subrectangular; carpus oval, 1.8 x as long as broad with 3 conical teeth, 1 small tooth on the middle of the distal margin, 1 long at the posterodistal corner and 1 on the posterior margin; propodus somewhat expanded distally, anterior margin almost straight, posterior margin distally convex; dactylus proximally expanded with anterior margin straight and posterior margin proximally convex, distal half of inner margin with 3 small and one long spine (serrated inner margin of dactylus in immature male) ( Fig. 10 : G1). Gnathopod 2 coxa subrectangular; basis 3.4 x as long as broad, posterior margin sparsely setose; ischium subquadrate; carpus 2.1 x as long as broad, posterior margin setose; propodus subrectangular, slightly longer than one third of the carpus, palm straight; dactylus slightly longer than palm, inner margin serrated ( Fig. 10 : G2). Pereopod 3–4 similar; basis around 3 x as long as broad; dactylus 0.85 x as long as propodus ( Figs. 10 : P3 & P4). Pereopod 5–7 length ratio 1:1.62:1.92. Pereopod 6 posterior margin sparsely setose with simple setae ( Figs. 10 : P5–P7). Pereopod 7 basis posterior margin densely setose with plumose setae ( Fig. 10 : P7).

Pleon. Eprimera 1–3 ventral margin rounded with a posteroventral seta ( Figs. 11 : Ep1–Ep3). Uropod 1 peduncle slightly longer than subequal rami; inter ramus spine 0.3 x as long as exopod ( Fig. 11 : U1). Uropod 2 peduncle subequal to exopodite; endopodite a little longer than endopodite ( Fig. 11 : U2). Uropod 3 uniramous; ramus almost 3 x as long as peduncle ( Fig. 11 : U3). Telson as long as broad, ventral margin bifid, both lobes with 3 apical setae ( Fig. 11 : T).

Female (sexually dimorphic characters). Gnathopod 1 subchelate, propodus subrectangular; palm oblique; dactylus longer than palm, inner margin serrated. Gnathopod 2 propodus subrectanhular, narrower than gnathopod 1 proposus, dactylus subequal to palm, inner margin weakly serrated.

Habitat. Muddy substrate. Salinity 13±2 ppt.

Remarks.

Eight species of the genus Grandidierella Coutière, 1904 have been reported from India so far including G. rabindranathi sp. nov. (Thacker et al. 2023). According to the diagnostic characters given by the ( Myers et al. 2019), the present species belongs to the Grandidierella mahafalensis Coutière, 1904 species-complex. Among the species of this complex, G. rabindranathi sp. nov. is very similar to G. mahafalensis Coutière, 1904 and G. nioensis Myers, Sreepada & Sanaye, 2019 by having long and slender male gnathopod 1 carpus posterodistal spine and male gnathopod 2 coxa ventral margin without spine. But it can be differentiated from these two species in number of ways. Male gnathopod 1 propodus in G. rabindranathi sp. nov. is oval with posterior margin convex (subrectangular with posterior margin substraight in G. mahafalensis and G. nioensis ); male G2 basis only 3.4 x as long as broad in G. rabindranathi sp. nov. (about 3.7 has long as broad G. mahafalensis and more than 4 x as long as broad in G. nioensis ); female gnathopod 1 basis 3 x as long as broad in G. rabindranathi sp. nov. (little over 2 x as long as broad in G. mahafalensis and nearly 4 x as long as broad in G. nioensis ).

Distribution. Currently known only from the type locality.

Figures

FIGURE 2. (a) Parhyale kalinga sp. nov., male paratype (LFSC.ZRC-200): 7 mm, Kalupada Ghat; (b) Chilikorchestia chiltoni gen. nov. sp. nov., male paratype (LFSC.ZRC-202): 11 mm, Honeymoon Island; (c) Grandidierella rabindranathi sp. nov., male paratype (LFSC.ZRC-204): 6 mm, Barkuda Island; (d) Quadrivisio bengalensis Stebbing, 1907, male (LFSC.ZRC-205): 9 mm, Kalupada Ghat, Chilika Lake, Odisha, India. Scale bars—1 mm.

FIGURE 9. Grandidierella rabindranathi sp. nov., male holotype (LFSC.ZRC-203): 6.5 mm, Barkuda Island, Chilika Lake, (19°33'12"N 85°08'07"E), Odisha, India. Scale bars—0.3 mm.

FIGURE 10. Grandidierella rabindranathi sp. nov., male holotype (LFSC.ZRC-203): 6.5 mm, Barkuda Island, Chilika Lake, (19°33'12"N 85°08'07"E), Odisha, India. Scale bars—0.5 mm.

FIGURE 11. Grandidierella rabindranathi sp. nov., male holotype (LFSC.ZRC-203): 6.5 mm, paratype female (LFSC.ZRC- 204): 5.5 mm, Barkuda Island, Chilika Lake, (19°33'12"N 85°08'07"E), Odisha, India. Scale bars—0.5 mm.