title: Cytogenetics and karyosystematics of South American oryzomyine rodents (Cricetidae: Sigmodontinae). IV. Karyotypes of Venezuelan, Trinidadian, and Argentinian water rats of the genus Nectomys.
abstract: Bone marrow chromosomes were studied in South American water rats of the genus Nectomys from Venezuela, Trinidad, and Argentina. Specimens of N. squamipes from western and southern Venezuela showed a 2n = 52-53 karyotype, whereas a 2n = 56-57 karyotype was found in specimens from northeastern Argentina. In both cases, odd karyotypes can be explained by the presence of a supernumerary chromosome. In contrast, water rats from northeastern Venezuela and Trinidad showed a strikingly reduced 2n = 16-17 polymorphic chromosome complement. Six different karyomorphs were found among the latter, which may have resulted from a combination of pericentric inversions in two pairs of autosomes and a centromeric fusion in another autosomal pair. It is proposed that the new 2n = 16-17 cytotypes belong to a species of its own, for which the name N. palmipes is suggested.
authors.affiliation: Departamento de Ciencias Biológicas, Universidad de Buenos Aires, Argentina.
authors.forename: M A
authors.initials: MA
authors.lastname: Barros
authors.forename: O A
authors.initials: OA
authors.lastname: Reig
authors.forename: A
authors.initials: A
authors.lastname: Perez-Zapata
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000145:classification / Q000235:genetics*; D002869:Chromosome Aberrations; D002875:Chromosomes; D005260:Female; D007621:Karyotyping; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics*; D013020:South America