REGISTRO DE POLIPLOIDIA EN LA ALMEJA DULCEACUICOLA MUSCULIUM ARGENTINUM (D'ORBIGNY 1835) (SPHAERIIDAE, VENEROIDA)

the polyploidy is an unusual character in bivalve mollusks. however, cytogenetic data documented for north-hemispheric species of the subfamily sphaeriinae (family sphaeriidae), showed chromosome numbers ranging from 36 to ca. 247. the freshwater clam musculium argentinum (d'orbigny 1835) has a polyploid chromosome number 2n = ca. 130, which shows that polyploidy likewise may be present in south american sphaeriids. these cytogenetic data suggest that the subfamily sphaeriinae could constitute a mature polyploid complex