Linguimaera mannarensis (Sivaprakasam)

Krapp-Schickel, T., 2003, Linguimaera Pirlot, 1936 (Crustacea, Amphipoda, Melitidae), a valid genus, Memoirs of Museum Victoria 60 (2), pp. 257-283 : 276-277

Linguimaera mannarensis (Sivaprakasam)

Ceradocoides chiltoni .— Sivaprakasam, 1968a: 109–111, fig. 11 (not Ceradocoides chiltoni Nicholls, 1938 ).

Maera mannarensis Sivaprakasam, 1968b: 274–278 , figs 1–2.

Maera mastersi . — Sivaprakasam, 1970: 36, fig. 1 a–g.

(not Megamoera mastersii Haswell, 1879a: 265 , pl. 11, fig. 1).

Type locality. Gulf of Mannar , India .

Diagnosis. Gnathopod 1 propodus medially widened, 2.4 times longer than wide, palm oblique, straight; gnathopod 2 male strongly asymmetrical, larger propodus pyriform, with rectangular hump near dactylus insertion and deep U-shaped incision, defined by a sharp tooth; carpus triangular, shorter than broad; pereopod 7 basis rounded, posterior margin serrated, propodus posterior margin with 3 groups of long robust setae and a fourth posterodistally; uropod 3 rami twice as long as peduncle, apically truncate, richly beset with robust setae. Telson with long apical robust seta, length twice the depth of incision of lobes and more than one third of telson length, with 2 strong robust setae mediolaterally.

Description. Adults 8–9 mm.

Lateral cephalic lobes rounded, with notch, anteroventral corner rounded. Eyes inferior part a bit widened, medially not narrowed.

Antenna 1 about 0.6 of body length; peduncle as long as flagellum, peduncle article 1 shorter than article 2; flagellum of 26–29 articles, accessory flagellum of 4–5 articles; antenna 2 slender, gland cone short, peduncle article 4 shorter than article 5, flagellum longer than article 5, of 11 articles.

Mandibular palp article 1 longer than wide; ratio article 2: article 3 = 1.2 (thus article 3 relatively long compared to other species); both with long setae, especially many dense on article 3 distally.

Gnathopod 1 sexual dimorphism not found. Coxa 1 anterodistally a bit upturned, bluntly pointed; basis ratio length: breadth = 3, posteriorly 5 long setae and some shorter ones; merus posteroventrally rounded (sharp tooth lacking here), twice as long as wide; carpus triangular, swollen; propodus slender, less broad than carpus, 3 times as long as wide, palmar corner scarcely defined.

Gnathopod 2 male strongly dimorphic, carpus in larger gnathopod short, shorter than broad; palmar corner well developed, with upturned point, followed by U-shaped incision defined by a straight blunt distal elevation of palm; no especially prominent robust seta except some submarginal along palm; dactylus strongly curved, the bend being stronger than the outline of propodus, thus inwards folded.

Pereopods 3, 4 very similar in shape and also size; pereopods 5, 6 robust, basis rectangular, small serrations on posterior margins, posterodistal corner slightly lengthened and not widened; pereopod 7 basis much larger, posterior margin rounded, serrated; robust setae on posterodistal corner of carpus reaching or surpassing half length of propodus.

Epimeral plate 3 with serration of 3 or 4 teeth.

Uropod 1 peduncle inferior margin subproximally with 1 strong robust seta, rami shorter than peduncle, outer a bit shorter; uropod 2 outer ramus as long as peduncle, inner a bit longer; uropod 3 much longer than uropods 1 and 2, rami subequal, truncate, beset with many short robust setae of maximally one fifth ramus length.

Telson longer than wide, lobes outer end longer than inner one; in excavation 1 strong robust seta inserted (one third of telson length) without small additional ones. Outer margin medially and on proximal third, 1 other, shorter robust seta.

Distribution. Gulf of Mannar, India; seaweeds.

Discussion. I have not seen this species, thus the description relies on Sivaprakasam's papers. According to them, this species differs from all other species by the the inwardly-bent dactylus and cup-shaped short carpus on the larger male gnathopod 2, the widened and serrate basis of pereopod 7 with long, rich setation on other articles and a relatively long mandibular palp article 3.