On a New Species of Macrobrachium (Decapoda, Palaemonidae) from Ithikkara River, South-West Coast of India
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ON A NEW SPECIES OF MACROBRACHIUM (DECAPODA, PALAEMONIDAE) FROM ITHIKKARA RIVER, SOUTH-WEST COAST OF INDIA BY V. UNNIKRISHNAN1),P.M.PILLAI1,3) and K. V. JAYACHANDRAN2) 1) P. G. Department of Zoology and Research Centre, Mahatma Gandhi College, Thiruvananthapuram, Kerala, India 695004 2) College of Fisheries, Panangad, Cochin, Kerala, India ABSTRACT Macrobrachium madhusoodani new species is described from the upper reaches of Ithikkara River, Kerala, South India. The species shares certain characters with M. scabriculum (Heller, 1862), M. aemulum (Nobili, 1906), and M. nobilii (Henderson & Matthai, 1910) in the number and arrangement of rostral teeth, while it differs remarkably from those three species in distinctive diagnostic characters: rostral formula 10-14/2-3 with 5-6 postorbital teeth; carapace smooth with distal end of rostrum straight; chelae with 4 denticles in the movable and 3 in the immovable finger, in the proximal part of the cutting edge; the distal part of the fingers of the second chelate legs are darkly pigmented except the tip. Three prominent pigment spots are found midlaterally on the last three abdominal somites, with prominent pigmentation at the tip of the telson. RÉSUMÉ Macrobrachium madhusoodani sp. nov. est décrite des cours supérieurs de la rivière Ithikkara, Kerala, au sud de l’Inde. L’espèce partage certains caractères avec M. scabriculum (Heller, 1862), M. aemulum (Nobili, 1906), et M. nobilii (Henderson & Matthai, 1910), en particulier le nombre et l’arrangement des dents rostrales, tandis qu’elle diffère remarquablement de ces trois espèces par des caractères diagnostiques: formule rostrale 10-14/2-3 avec 5-6 dents post-orbitales, carapace lisse avec l’extrémité distale du rostre droite ; pinces avec 4 denticules sur le doigt mobile et 3 sur l’autre, situées dans la partie proximale du bord tranchant ; parties distales des doigts des secondes pattes fortement pigmentées excepté à l’extrémité. Trois taches fortement pigmentées sont présentes médio-latéralement sur les trois derniers somites abdominaux, avec une pigmentation remarquable à l’extrémité du telson. 3) e-mail: [email protected] © Koninklijke Brill NV, Leiden, 2010 Crustaceana 83 (9): 1115-1123 Also available online: www.brill.nl/cr DOI:10.1163/001121610X521253 1116 V. UNNIKRISHNAN, P. M. PILLAI & K. V. JAYACHANDRAN INTRODUCTION Freshwater prawns of the family Palaemonidae (Decapoda, Caridea) comprise two subfamilies, viz., Palaemoninae and Pontoniinae. Palaemoninae has a vast and diverse species assemblage, consisting of 21 genera and approximately 300 species. By far the largest genus, distributed in tropical, subtropical, and temperate regions, is Macrobrachium Bate, 1868. Holthuis (1949, 1950a, b, 1984) recorded several species of Macrobrachium from different countries, and Tiwari (1955) extensively studied the species and subspecies of Indian freshwater prawns of the genus Palaemon. Jayachandran (1987, 1991, 2001) and Jayachandran & Joseph (1985a, b, c, 1988, 1989) have studied the distribution of palaemonid prawns in certain rivers and estuaries of India. During a survey for the study of palaemonid prawns along the southwest coast of India, the present authors collected several species from the upper reaches of Ithikkara River (>120 m above Mean Sea Level), Kerala, India. Among these, 10 specimens showed morphometric and meristic characters that did not conform to any other known species of Macrobrachium and these are hence described as a new species, herein. SYSTEMATIC PART Macrobrachium madhusoodani sp. nov. (figs. 1-2) Material examined. — Among 10 specimens collected from the upper reaches of the Ithikkara ◦ ◦ River, (8 56 42 N76 56 20 E) Kerala, South India, 26 January 2009, 7 are males and 3 are mature females. One male specimen is described here as the holotype (no. 7). The paratypes (nos. 1-6 and 8- 10) are currently stored in the Natural History Museum of the Postgraduate Department of Zoology and Research Centre, Mahatma Gandhi College, Thiruvananthapuram, Kerala, S. India. Measurements of holotype in mm (specimen no. 7, table I). — Total length, 38; carapace length, 11; length of rostrum, 6; length of telson, 5; first chelate leg: ischium (i) 2.0; merus (m) 3.8; carpus (c) 4.7; propodus (p) 2.0; dactylus (d) 0.9. Right second chelate leg (large): i = 4.0, m = 5.0, c = 5.0, p = 10.5, d = 5.0. First non-chelate leg (pereiopod 3): i = 2.0, m = 4.5, c = 1.9, p = 4.0, d = 1.0 Second non-chelate leg (pereiopod 4): i = 2.1, m = 4.6, c = 2.0, p = 4.0, d = 1.0 Third non-chelate leg (pereiopod 5): i = 2.8, m = 4.6, c = 2.5, p = 4.9, d = 1.0 Description. — Rostrum moderately long, but not reaching tip of antennal scale, basal crest not much raised and distal end directed forwards. Dorsal margin of rostrum with 10-14 teeth, 6 postorbital and the rest preorbital (table I). Rostral teeth evenly distributed in smaller specimens, but the proximal 3 teeth unevenly distributed in larger specimens. Ventral margin of rostrum with 2 teeth, rarely 3. Small setae are present between the teeth, on both the dorsal and ventral margins..