The Freshwater P
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MACROBRACHIUMSIRINDHORN N.SP.,ANEWFRESHW ATERPRAWN FROMNORTHERN THAILAND (DECAPODA, CARIDEA, PALAEMONIDAE) BY PHAIBUL NAIYANETR Departmentof Biology,Faculty of Science,Chulalongkorn University, Bangkok, Thailand ABSTRACT Anewspecies of Macrobrachium , M.sirindhorn ,belongingto the group of Macrobrachium pilimanus (DeMan), is described from Thailand. A comparisionis made with the other known speciesof the M.pilimanus group. RÉSUMÉ Unenouvelle espè ce de Macrobrachium , M.sirindhorn ,appartenantau groupe de Macro- brachiumpilimanus (DeMan) est dé crit de Thaïlande. Elle est comparé e auxautres espè ces connues du groupe M.pilimanus . INTRODUCTION Thefreshwater prawnsof Thailand (Palaemonidae) are still poorlystudied. Recently,a studyof specimens fromnorthern Thailand revealed the presenceof anewspecies belongingto the Macrobrachiumpilimanus group.The new species is heredescribed under the name Macrobrachiumsirindhorn . Theholotype of the newspecies is depositedin the collection ofthe National Museumof Natural History,Leiden, The Netherlands (RMNH), and the paratypes are depositedin the collection ofChulalongkorn University ,Museumof Zoology, Bangkok,Thailand (CUMZ), in the ZoologicalReference Collection (ZRC)of the Rafes Museum,National University ofSingapore, and in the Museumnational d’Histoire naturelle, Paris (MNHN). Theabbreviation cl. is usedfor carapace length. c KoninklijkeBrill NV ,Leiden,2001 Crustaceana 74(7):609-616 ° 610 PHAIBUL NAIYANETR Macrobrachiumsirindhorn newspecies (gs. 1-2, pl. 1) Material.— Holotype:1 male,cl. 17.6 mm, RMNH D48632(ex. CUMZ, CU1997.162),Pong Nam DungW aterfall,Mae Soon, Amphoe Fang, Chiang Mai Province, northern Thailand, 23 April 1976,leg. P .Naiyanetr.Paratypes: 3 males,cl. 10.7-17.0 mm, ZRC andCUMZ, samedata as holotype;1 male,cl. 16.2 mm, ZRC, CU1997.166,Ban Y angW aterfall,Mae Ngon, Amphoe Fang, ChiangMai Province, 1 May1977; 1 male,cl. 14.0 mm, 1female,cl. 8.0 mm, ZRC, CU1997.165, PhuSang Waterfall, Amphoe Chiang Kham, Phayao Province, 29 April 1976. Other specimens: 1specimen,ZRC, CU1997.164,Huai Chongkham, Amphoe Muang, Mae Hong Son Province, 23March 1979; 6 specimens,ZRC, CU1997.161,Huai Khan, Amphoe Muang, Mae Hong Son Province,23 March1979; 1 male,cl. 16.2 mm, ZRC, CU1997.139,Ban Y angWaterfall, Mae Ngon, AmphoeFang, Chiang Mai Province, 21 April1976; 1 specimen,CUMZ, CU1997.163,stream near PongNam Ron,Amphoe Fang, Chiang Mai Province, 24 April 1976, leg. P .Naiyanetr;3 specimens (MNHN), northernThailand, leg. A. Pavie. Etymology.—Thespeci c nameis givenin honourof Her Royal Highness Princess MAHACHAKRI SIRINDHORN, as atokenof recognition of Hergreat interest in the studyof the natural history ofThailand. Her Royal Highness graciouslypermitted the use ofHername for this interesting species. TheThainame for this species is KungChao Fa andthe proposedEnglish name Waterfall prawn. Description ofadult male. —Rostrum short,straight orslightly convex,reach- ingto base ofthird segment ofantennular peduncle or to the endof that segment; rostral formula3-4+5-7/ 2-3.Antennal and hepatic spines small. Carapacesmooth exceptfor some small spinules onloweranterolateral region.Antennular pedun- cle 0.45times as longas carapace.Third thoracic sternite with indistinct trans- verse ridge,fourth thoracic sternite withoutmedian process. Abdomen smooth, glabrous, rst to third pleurites broadlyrounded, fourth and fth pleurites feebly producedposteriorly ,fourthpleurite subtriangular, fth pleurite subrectangular, sixth abdominalsomite 1.5times as longas fth,with posterolateral anglestrongly produced,acute, posteroventral angle feebly produced, subacute. Telson 1.4 times lengthof sixth abdominalsomite, with twopairs ofsmall dorsal spines; posterior marginending in amedianpoint, lateral spines small, smaller thandorsal spines, intermediate spines well developed,with aboutsix pairs oflong,plumose setae. First to third abdominalsterna with transverse ridge,with mediantooth, that of rst twoabdominal sternites similar to eachother, larger andbroader than the fol- lowing,that ofthird sternite small butmore pointed compared to the previoustwo, fourthand fth sternites with indistinct bluntlytriangular ridges,preanal region with triangular carina. Eyeswell developed,cornea longer and broader than stalk, about0.15 times as longas carapace.Basal segment ofantennularpeduncle broad. Stylocerite dis- tinctly pointed,reaching middle ofbasal segment.Anterolateral toothreaching .