INDUCTION OF C- AND G-TYPE BANDS ON IN VIVO METAPHASE CHROMOSOMES OF THREE SPECIES OF LARVIVOROUS FISHES

Induction of C-or G-bands on in vivo metaphase chromosomes in fish is extremely difficult and needs a lot of variations in the pre-treatment schedule. In the present study, C- and G-type bands could be successfully induced in three species of larvivorous fishes, namely, Chanda nama (Fam : Centropomidae), Esomus dan rica and Puntius ticto (Fam : Cyprinidae) by deploying the BSG method with some minor modifications. While C nama showed localization of C-band heterochromatin mostly at or near the centromeric regions of the acrocentric chromosomes, E. danrica had mostly pericentric locations except for 2 to 3 pairs showings the entire chromosome length as C-band positive. On the other hand, P. ticto tended to show blocks of heterochromatin on the whole or one arm of several chromosome pairs (3 to 4 pairs), apart from a few pairs that either had centromeric or telocentric locations. Serial bands could be noted across the whole length of the metaphase chromosome of both C. nama and P. ticta, including several chromosomes showing Cbands as well. However, the G-type bands in E. danrica were not so well-defined, several pairs showing apparently lateral assymetry in band localization

Cytogenetic studies of two freshwater sciaenids of the genus Plagioscion (Perciformes, Sciaenidae) from the central Amazon

Cytogenetic characterization of two freshwater sciaenid species from the genus Plagioscion (P. squamosissimus and Plagioscion sp.) was obtained for the first time. Giemsa staining, Ag-NOR and C-banding revealed that both species presented 2n = 48 chromosomes (almost all acrocentric). Single NORs and heterochromatin were found mainly at the pericentromeric position. Karyotypic formulae and NOR location proved to be valuable in showing both interspecific and intraspecific differences. All chromosomes were acrocentric in P. squamosissimus. NORs were located at proximal positions on the long arms of the last chromosome pair of the complement, and were heteromorphic due to size differences. Such heteromorphic NORs seem to be associated with each population sampled. Plagioscion sp. presented two cytotypes: cytotype a (2M + 46A) and cytotype b (48A). In both cytotypes, NOR-bearing chromosomes were located at the proximal position on the long arms of the first chromosome pair of the complement. However, NOR-bearing chromosomes were metacentric in cytotype a and acrocentric in cytotype b.<br>Foram estudados, pela primeira vez, os cariótipos de duas espécies de sciaenídeos de água doce, pertencentes ao gênero Plagioscion (P. squamosissimus e Plagioscion sp.), através de técnicas de coloração convencional (Giemsa), NOR e banda C. Todos os indivíduos apresentaram 2n = 48, NOR simples e banda C preferencialmente pericentromérica. Porém, a fórmula cariotípica e a localização das NORs permitiram-nos evidenciar diferenças inter- e intra-específicas. Em P. squamosissimus, as NORs estão localizadas em posição proximal nos braços longos do último par do complemento e são heteromórficas em relação ao tamanho das marcações. Aparentemente, esse heteromorfismo de NOR está associado com diferenças populacionais. Por outro lado, Plagioscion sp. apresentou dois citótipos. O citótipo a é caracterizado por 2 cromossomos metacêntricos e 46 acrocêntricos, enquanto o citótipo b é caracterizado por 48 cromossomos acrocêntricos. Em ambos citótipos, as NORs estão localizadas em posição proximal nos braços longos do primeiro par de cromossomos do complemento. Porém, no citótipo a essas marcações localizam-se em um par de cromossomos metacêntricos, enquanto no citótipo b em um acrocêntrico

New developments in vertebrate cytotaxonomy III. Karyology of bony fishes: A review

[No abstract available