Grandidierella megnae ( Giles, 1890 )

Thacker, Dimple R., Patro, Shesdev, Bhoi, Gitanjali, Myers, Alan A., Kumar, R. Kiran & Trivedi, Jigneshkumar N., 2025, On the genus Grandidierella Coutière, 1904 (Amphipoda: Aoridae) of India with the description of two new species, Zootaxa 5716 (4), pp. 451-482 : 472-476

Grandidierella megnae ( Giles, 1890)

Figs. 2B , 13 & 14

Microdeutopus megnae Giles, 1890 , 231, figs 1–4.

Grandidierella bonnieri — Stebbing 1908: 120, Pl. VI.

Diagnosis

Male gnathopod 1 carpus large with posterodistal corner produced into a large conical tooth and inner surface with a small accessory tooth. Dactylus inner margin smooth with few small hairs, proximally expanded.

Material examined

India • 3 ♂, 4.0–5.0 mm; Tithal , Gujarat; 20°35'26"N, 72°48'45"E; 12 Mar 2024; D. R. Thacker leg.; LFSC.ZRC-288 .

Ecology type. Collected from Muddy substrate. Salinity 35±2 PSU .

Description. Based on male 5 mm.

ANTENNA 1 ( Fig. 13 ). Slender, about 1.3 × the length of antenna 2; length ratio of peduncular articles 1–3 1:1.28:0.56; primary flagellum subequal to peduncle; accessory flagellum minute.

ANTENNA 2 ( Fig. 13 ). Stout, length ratio of peduncular articles 3–5 1:2.45:2.49; flagellum short with 7 articles, article 3 to 7 each with a robust spine.

MAXILLA 1 ( Fig. 13 ). Outer plate with several apical robust setae, palp article 2 with 6 apical robust setae.

MAXILLA 2 ( Fig. 13 ). Inner plate with several apical and 3 marginal setae and a sparse row of setae, outer plate apically setose.

MAXILLIPED ( Fig. 13 ). Inner plate with several plumose setae; outer plate with 4 apical thick setae and 5 robust marginal setae; palp article 2 longest, inner margin densely setose; article four with apical nail.

GNATHOPOD 1 ( Fig. 14 ). Coxa subrectangular, longer than broad, anteroventral corner produced; basis 1.7 × longer than broad with a single seta on anterior margin; ischium broader than long, subrectangular; carpus large, elongate, 1.8 × longer than broad with a long conical tooth at posterodistal corner; propodus both margins convex; dactylus inner margin smooth with few small hairs, proximally expanded.

GNATHOPOD 2 ( Fig. 14 ). Coxa subrectangular, longer than broad; basis 3.4 × the length as broad, posterior margin sparsely setose; ischium subquadrate; carpus 2.6 × longer than broad, both margins setose; propodus somewhat oval, 0.7 × the length of carpus, palm with several setae; dactylus subequal in length to palm, distal half of the inner margin serrated.

PEREOPOD 3–4 ( Fig. 14 ). Similar; basis around 3.3 × longer than broad; ischium small, subrectangular; merus subequal to propodus, both margins with 2–3 setae on each side, 2 long setae on both distal corners; carpus with a single small seta on anterior margin and several long setae on posterior margin; propodus slender, with few setae on both margins and a tuft of setae on anterodistal corner; dactylus subequal to carpus, slender.

PEREOPOD 5 ( Fig. 14 ). Shorter than pereopod 4; basis anterior margin with very few small setae, posterior margin with sparsely placed short and long setae; ischium small; merus subequal to carpus with thick setae on anterior margin, posterior margin with a small seta, posterodistal corner with a long thick seta; carpus anterior margin with three small to long setae, posterior margin with three spines; dactylus short, less than one third of the propodus.

PEREOPOD 6 ( Fig. 14 ). 0.9 × the length of pereopod 7; basis subrectangular, anterior margin with 7 small robust setae, posterior margin with few robust setae and sparsely placed plumose setae; ischium longer than broad with one long, thick seta at anterior margin; merus 5.7 × longer than broad, anterior margin with one seta, posterior margin with four setae, anterodistal corner with two short setae, posterodistal corner with one long setae; carpus 0.9 × the length of merus, anterior margin with 2 and posterior margin with 3 short setae, both distal corners with a tuft of two thick setae; propodus subequal to basis, anterior margin with 4 robust setae; dactylus nearly one third of the propodus.

PEREOPOD 7 ( Fig. 14 ). Basis anterior margin with 6 small robust setae, posterior margin sparsely 7–8 small robust setae and spaced apart plumose setae; ischium small with one seta at anterior margin and one seta at anterodistal corner; merus subequal to basis, both margins with several setae, anterodistal corner with one simple and one robust setae, posterodistal corner with one long simple seta; carpus 0.8 × the length of merus; propodus subequal to basis; anterior margin with four small setae, posterior margin with two robust setae, posterodistal corner with a tuft of long setae; dactylus one third of the propodus.

EPIMERA 1–3 ( Fig. 13 ). Ventral margin bare and anterior and posterior corners rounded.

UROPOD 1 ( Fig. 14 ). Peduncle 1.2 × longer than both subequal rami; inter ramus spine 0.2 × the length of exopod.

UROPOD 2 ( Fig. 14 ). Peduncle subequal to endopodite; exopodite 0.7 × the length of endopodite.

UROPOD 3 ( Fig. 14 ). Uniramous; ramus almost 2.9 × the length of peduncle.

TELSON ( Fig. 13 ). Longer than broad, ventral margin with a small inward curve, laterodistal corner each with one long seta.

Remarks

Giles (1890) described Microdeutopus megnae based on specimens collected from Meghna Shoals, Bangladesh. Later, this species was transferred to the genus Grandidierella by Stebbing (1908) based on specimens collected from Port Canning, West Bengal, India, under the name Grandidierella bonnieri , later synonymized with G. megnae . The specimen dissected here agrees with the description and illustrations of G. megnae ( Giles, 1890) .

Distribution

Megna shoals, Bangladesh ( Giles, 1890); Port Canning, West Bengal, India ( Stebbing, 1908); Mozambique, South Africa (Barnard, 1955) and Tithal, Gujarat, India (Present study). In the present study this species is first time reported from Gujarat State, India.

Figures

FIGURE 2. A. Grandidierella macronyx K.H. Barnard, 1935, ♂, (LFSC.ZRC-287). B. Grandidierella megnae (Giles, 1890), ♂, (LFSC.ZRC-288).

FIGURE 13. Grandidierella megnae (Giles, 1890), 1935, ♂, (LFSC.ZRC-288). Scale bars: 0.13 mm.

FIGURE 14. Grandidierella megnae (Giles, 1890), 1935, ♂, (LFSC.ZRC-288). Scale bars: 0.25 mm.