Grandidierella nioensis, Myers & Sreepada & Sanaye, 2019

Myers, Alan A., Sreepada, Rayadurga A. & Sanaye, Sushant V., 2019, A new species of Grandidierella Coutière, 1904, G. nioensis sp. nov. (Amphipoda, Aoridae), from the east coast of India, Zootaxa 4544 (1), pp. 119-124 : 120-123

Grandidierella nioensis sp. nov.

( Figs 1 , 2)

Type material. Male holotype, 6.0 mm. (NHMUK 2018.1536) Palakayatippa village, Machilipatnam, Andhra Pradesh, east coast of India (15°58'54.32''N; 81°05'51.88''E), shrimp pond bottom, silty-clay, coll. R.A. Sreepada, 30 May, 2009.

Paratypes ( NHMUK 2018.1537 ), 300+ males and females, same data as holotype .

Type locality. Palakayatippa village, Machilipatnam, Andhra Pradesh, east coast of India.

Etymology. Named after the Institute where the species is presently being cultured.

Description. Based on male holotype 6.0 mm.

Head. Ocular lobes obtuse; eyes of moderate size, black. Antenna 1 peduncular articles in the ratios 8:11:3; primary flagellum sub-equal in length with peduncle with 22 articles; accessory flagellum minute with one rudimentary articulate. Antenna 2 subpediform, subequal in length with antenna 1; articles 4 and 5 subequal in length; flagellum with 6 articles each with robust seta and several fine setae. Mandible palp article ratios 3:4:4, article 3 subrectangular, with long apical and subapical setae.

Pereon. Pereonite 1 with large, forward directed sternaI spine. Gnathopod 1 coxa a little broader than long, subrectangular, anterior margin rounded, unproduced; basis 2.5 × as long as broad, weakly setiferous; carpus large, subrectangular, posterior margin substraight, 2.5 × as long as broad, posterior distal margin produced into a short, triangular, weakly deflected spine, proximal to which on distal margin is a shorter conical tooth, inner face of posterior margin with a small mediosubmarginal spine; propodus moderately expanded distally, posterior margin convex distally, weakly concave proximally; dactylus elongate, scythiform, posterior margin crenulate. Gnathopod 2 coxa subquadrate; basis elongate, more than 4 × as long as broad, anterior margin straight; carpus elongate, a little less than 3 × as long as broad, anterior margin weakly setiferous; propodus a little over two thirds length of carpus with weakly convex anterior and straight posterior margin, palm oblique, lacking robust setae; dactylus slightly overlapping palm. Pereopods 3–4 coxae evenly convex anteriorally, produced into a triangular process posteriorally. Pereopods 5–7 in length ratios 4:6:7; pereopod 7 basis with long plumose setae on posterior margin.

Pleon. Epimera 1–3 rounded, each with a single posteroventral seta. Uropod 1 peduncle a little longer than rami, with a stout, distal, inter-ramal spiniform process; rami subequal. Uropod 2 peduncle broad, subequal in length with outer ramus, lacking an inter-ramal process; inner ramus longer than outer. Uropod 3 uniramous; peduncle subsquare, with strongly expanded flange on inner margin; ramus 3 × length of peduncle with a small second article and many long marginal and distal setae. Telson as broad as long with nearly straight ventral margin, dorsolateral crests each with a group of 3 long setae, lateral margins each with 2 setae.

Female 5.0 mm (sexually dimorphic characters). Gnathopod 1 basis nearly 4 × as long as broad, anterior margin concave; carpus 2 × as long as broad; propodus about four fifths length of carpus, subovoid, palm oblique, not clearly defined from posterior margin, which bears 6 strong robust setae; dactylus elongate, three quarters length of propodus.

Remarks. Grandidierella nioensis sp. nov. is most similar to G. mahafalensis Coutière 1904 , from a freshwater lake in Madagascar. It differs primarily in the shape of the male gnathopod 1 in which the posterodistal spine is short and triangular in G. nioensis sp. nov. but long and slender in G. mahafalensis . It also differs from G. mahafalensis in its much more slender gnathopods. The basis of the male gnathopod 1 is 2.5 × as long as broad in G. nioensis sp. nov. but only 2 × as long as broad in G. mahafalensis . Similarly in male gnathopod 2 the basis is over 4 × as long as broad in G. nioensis sp. nov., but less than 3 × as long as broad in G. mahafalensis . In the female, the basis of gnathopod 1 of G. nioensis sp. nov. is very long and slender (nearly 4 × as long as broad) and the anterior margin is strongly concave, whereas in G. mahafalensis , the basis is short and stout (about 2 × as long as broad) with the anterior margin substraight. It is also very similar to G. halophilus Wongkamhaeng, Pholpunthin & Azman, 2012 , from saltpans in the Gulf of Thailand. That species has a very similar male gnathopod 1 to G. nioensis sp. nov., however, in G. halophilu s the male coxa 2 has the ventral margin produced into a strong spine, absent in G. nioensis sp. nov. It is also broadly similar to G. bonnieroides Stephensen, 1948 , originally described from islands off Venezuela, but now known to be distributed worldwide probably through anthropogenic means. Grandidierella nioensis sp. nov. differs from G. bonnieroides in the shape of the male gnathopod 1. In G. bonnieroides , the carpus is distinctly subovoid, with the posterior margin convex, whereas in G. nioensis sp. nov. the posterior margin is substraight. In addition, the posterodistal spine in G. bonnieroides is elongate and slender not short and triangular as it is in G. nioensis sp. nov. In large adult G. bonnieroides , the dactylus of the male gnathopod 1 becomes short and swollen medially ( Myers, 2009), with a smooth posterior margin, but in G. nioensis sp. nov. it remains elongate and develops a crenulate posterior margin. Grandidierella nioensis sp. nov. differs from G. spinicoxa Myers, 1972 , in lacking the dense brush of setae on the anterior margin of the male gnathopod 2 carpus in that species.

Habitat. Specimens of G. nioensis sp. nov. were collected from the silty-clay/muddy bottom of shrimp ponds. Average depth of ponds was 1.2± 0.2 m and salinity of water in the range: 15–20 ppt.

Distribution. Currently known only from the type locality.

Discussion. Grandidierella nioensis sp. nov. belongs to a group of five extremely similar and difficult to separate Grandidierella species that constitute the Grandidierella mahafalensis Coutière, 1904 , species-complex. It is probable that further species currently attributed to G. bonnieroides Stephensen , may prove to be distinct species in this species complex.

Figures

FIGURE 1. Grandidierella nioensis sp. nov., male holotype, Machilipatnam, Andhra Pradesh.