Macrobrachium abrahami, Pillai, P. M., Unnikrishnan, V. & Kumar, U. Suresh, 2014

Pillai, P. M., Unnikrishnan, V. & Kumar, U. Suresh, 2014, Description, DNA barcode and phylogeny of a new species, Macrobrachium abrahami (Decapoda: Palaemonidae) from Kerala, India, Zootaxa 3768 (5), pp. 546-556 : 548-550

Macrobrachium abrahami sp. nov.

(Figs. 1–3)

Materials examined. Holotype: 1 male (no.1, table 2) (ZSI/ WGRS /IR/INV 2152), collected from Vamanapuram River (76°53΄54.00΄΄E, 8°43΄23.81΄΄N), Kerala, South India, 6 February 2007. Paratypes: 1 male (no. 5, table 2) (ZSI/ WGRS /IR/INV 2153), 6 males (nos. 2–4, 6–8) (MGC/TVM/NHM-INV/4/2012). The holotype and paratype (no. 5) are deposited in the faunal depository of the Zoological Survey of India, Western Ghats Regional Centre, Kozhikode, and the paratypes (nos. 2–4, 6–8) are stored in the Natural History Museum of the Post Graduate Department of Zoology and Research Centre, Mahatma Gandhi College, Thiruvananthapuram, Kerala, India.

Measurement of holotype in mm: total length, 57.0; carapace length, 17.0; length of rostrum, 7.5; length of telson, 7.0; first chelate leg: ischium (i) 3.0; merus (m) 5.0; carpus (c) 6.0; propodus (p) 3.0; dactyl (d) 0.6 Diagnosis. Rostrum: moderately long, distal end directed upwards, rostral formula 12–15/2–3, with 5–6 postorbital teeth; carapace smooth. Large second chelate leg: merus less than and propodus more than double ischium length; carpus equal to merus; ischium shortest, propodus longest. Fingers stout with 15 linear denticles on proximal half of cutting edge; pubescence restricted to base of fingers. Small second chelate leg: 6 small denticles at proximal cutting edge of fingers; 1 distal denticle comparatively larger. Dark pigment bands throughout the posterio-dorsal margin of uropodal exopod and endopod, its thickness equals the thickness of uropodal setae.

Description. (holotype): Rostrum moderately long, tip over reaching end of antennular peduncle, basal crest not much raised, distal end directed upwards. Dorsal margin of rostrum with 14 teeth, 5 postorbital (table 1). Rostral teeth evenly distributed in all specimens; ventral margin with 2 teeth, short setae between teeth.

FIGURE 1. Macrobrachium abrahami sp. nov., specimen no. 1, holotype (male). A, carapace-right lateral view; B, second large chelate; C, 2nd chela enlarged; D, telson and uropod; E, 3rd pereiopod, distal part; F, 3rd pleopod; G, 2nd pleopod of male; H, 1st chelate leg.

Carapace smooth, hepatic spine situated just below and behind antennal spine (figs. 1A, 2). Abdomen glabrous, pleurae of somites I–III typical, those of IV and V directed backward, and of VI ending in spine.

Telson conical with 2 pairs of spines on dorsal surface, proximal situated midway, and distal at about ¾ length. Posterior end of telson bears 2 pairs of movable spines, outer smaller, inner longer, and overreaching tip of telson; a few plumose setae between the inner pair of spines (fig. 1D). Antennules typical in structure; outer lateral spine of antennal scale sharp, pointed forwards.

First pair of chelate legs slender, tips of chelae over reaching antennal scale when extended. Ischium equal to propodus, shorter than merus; carpus twice as long as ischium, dactylus the shortest. Palm longer than fingers (fig. 1H).

Large second chelate leg strong; 0.72 times total body length; merus less than twice as long as ischium; propodus more than twice ischium. Carpus slightly shorter than merus, ischium shortest, propodus longest (fig. 1B). Fingers stout, equal, 15 denticles at proximal half of cutting edge, distal end curved, ratio of fingers to palm 1.25:1 (fig. 1C). Pubescence restricted to the basal part of fingers; very delicate setae present throughout the palm.

Second small chelate leg strong, 0.51 times total body length; ischium shorter than merus, merus shorter than carpus, carpus shorter than chela and slightly longer than palm. Palm equal to fingers; cutting edge of fingers bear 6 small denticles, distal one comparatively larger.

Non-chelate legs and pleopods normal in structure for the genus Macrobrachium (fig. 1E, F). The non-chelate legs progressively increase in length from first to third. Appendix interna more than half as long as appendix masculina, with spinous setae on inner side (fig. 1G).