CYTOGENETICS OF AQUARIUM FISHES .3. PROBLEMS OF KARYOTYPIC VARIABILITY IN THE FAMILY CHARACIDAE (PISCES, CHARACIFORMES) WITH THE DESCRIPTION OF SOMATIC KARYOTYPES FOR 6 SPECIES OF TETRAS

Somatic karyotypes of 6 species belonging to the subfamily Tetragonopterinae, family Characidae, are described: Hyphessobrycon scholzei—2n = 50 = 8M + 20SM + 8ST + 14A; H. herbertaxelrodi—2n = 52 = 10M, SM + 42ST, A; H. flammeus—2n = 52 = 18M, SM + 32ST + 2A; Hasemania marginata—2n = 50 = 12 M + 18SM + 10ST + 10A; Hemigrammus hyanuary—2n = 52 = 22M, SM + 30ST, A; Nematobrycon palmeri—2n = 50 = 8M, SM + 10ST + 32A. On the basis of karyotypic evolution in the family Characidae there are numerous inversions which have produced high morphological variability of karyotypes with simultaneous relatively constant diploid chromosome numbers. The process of karyotype symmetrization have no a stable direction even in lower taxa that have been resulted in the appearance of sufficient différencies between congeneric species and between species of closed genera on such characteristic as the arm chromosome number. The problem of ancestral karyotypic structure and some karyotaxonomical problems are discussed. © 1990 Taylor & Francis Group, LLC.