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NOTAsiatic Clam, orbicula fIumineain Northwestern PatagoniaArgentina

ABSTRACTThe invasive Asiatic clam, orbicul flumine Mller, 1778),is reported from the Negro River, at Chimpay, in the Patagonianshrubland. The invasion seems to have occurred in 1997-1998,

as revealed by its absence in the field assessments made up toJanuaty 1997 and the presence of a layer of orbicul emptyshells in the dry sand banks left by the flood of the river inwinter 1998.When the introduced Asiatic claros were found in the Colorado River

Argentina), this location was deemed to be on the southernmost latitudethe species could reach due to cold constraint Cazzaniga 1997). Thisstatement left open the possibility that the claros colonized thePatagonian zoogeographical realm Ringuelet 1961) to the West, on theupper part of the Negro River. This proved to be true with the fmding oforbicul flumine Mller, 1778) at Chimpay Ro Negro Province, 39 10S-66 10 W), where it probably entered during 1997.One of us CP) regularly does field work in the Chimpay area duringsummers except 1998). No live Asiatic claros were observed there untilJanuary 14, 1999, when the first samples were found. It is worth notingthat in Januaty 1997 the Negro River was canoed from Chimpay toViedma a distance of about 550 km), and nearly every 25 to 50 km asurvey was made by digging the coastal sand and by skin-diving.Although many samples were obtained, no orbicul flumine was foundin that caropaign.Notwithstanding, a flood in July 1998 winter) left some sand bankswith an abundance of orbicul flumine shells; thus a dense populationof the Asiatic claro had developed there, probably during the summertimeof 1997-1998 December-March).At present, populations of Asiatic claros are quite abundant in twosmall strearos flowing to the Negro River, 5 km from each other, near thetown of Chimpay. Claros were also collected in the Negro River itself, in apublic bath site 6 km to the east of Chimpay. Since this part of the riveris not navigable, the claro was not introduced accidentally va waterballast Ituarte 1994) but more likely was introduced by the fishermenwho used the claro as bait.Voucher specimens from Chimpay were deposited at Museo de LaPlata Argentina) 25 alcohol preserved claros; collection number 5430).Their measures are summarized in Table 1.

551Joumal 01F reshwater Ecology, Volume 14, Number 4 December 999

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Table 1. Measurements of the voucher specimens of Corbiculaflumineafrom Chimpay Argentina .N = 25 LengthjWidth

1.620.041.741.52

MeanStandard dev.MaximumMinimum

LITERATURE CITEDCazzaniga, N. J. 1997. Asiatic clam, Corbicula fluminea, reachingPatagonia Argentina . Joumal of Freshwater Ecology 12 4 :629-630.Ituarte, C. 1994. Corbiculaand Neocorbicula Bivalvia: Corbiculidae in theParan, Uruguay, and Ro de la Plata Basins. Nautilus 107 4 :129-135.Ringuelet, R. A. 1961. Rasgos fundamentales de la zoogeografia de laArgentina. Physis 22:151-170.

Nstor J. Cazzaniga and Cristian PrezUniversidad Nacional del SurDepartamento de Biologa, Bioqumica y Farmacia

8000 Baha Blanca, Argentina

552Received: 6 May 1999 Accepted: 27 September