Localisation of NORs and counterstain-enhanced fluorescence studies inPerca fluviatilis (Pisces, Percidae)

Abstract

The karyotype of the perch (Percafluviatilis L.) was analysed by means of silver-staining, the chromomycin A3/Distamycin A/DAPI and Actinomycin D fluorescence technique in order to locate active NORs and to selectively highlight certain heterochromatic regions. The ribosomal RNA genes are localized at the secondary constrictions of the short arms of chromosomes no. 16. Additionally, bright chromomycin fluorescence was observed in the same regions. No DAPI/Distamycin A bright heterochromatic block was detected in the perch karyotype. I:~,. I. Sequential Ag-CDD-DAPI Actinomycin D staining of a lymphocyte metaphase of a male perch: (a) Ag-NOR-staining, note two Ag-NORs on two chromosomes no. 16: (bJChromomycinstaining. note brilliant chromomycin fluorescence associated with NOR regions: {c) DAPI Distamycin A. notelack of differentially stained fluorescence block,: Id) DAPl'Actinomycin Dstaining.

Heterochromatin patterns and karyotype relationships within and between the genera Brycon and Salminus (Pisces, Characidae)

“…As, in general, reported for fishes (e.g. Mayr et al, 1985), these MM + bands appear coincident to AgNOR sites and also to C banded heterochromatin of both Brycon species. S. hilarii similarly showed only two MM + bands/cell, corresponding to AgNORs (data not shown), and again indicates a common pattern of chromosome evolution among these fish groups.…”

Cytogenetic Diversity in the Astyanax scabripinnis Species Complex (Pisces, Characidae) I. Allopatric distribution in a small stream.

“…Although the technique of Howell and Black (1980) stains only the NORs that were active during the preceding interphases, it should be pointed out that, even so, there was a great differentiation not only in the number of chromosomes bearing these active regions, but also in the real number of NOR-bearing chromosomes, since the DA/DAPI combination was used in the population that presented the smallest number of AgNOR+ chromosomes and stained negative bands (supposedly poor in AT base sequences) coinciding with AgNORs+. Using GC-specific fluorochromes (chromomycin A3 or mitramycin), some investigators have detected a close correspondence between GC base-rich chromsome regions and AgNORs+ (Mayr et al 1985, Amemiya and Gold 1986, Rab and Mayr 1987, Galetti and Rasch 1993, Souza et al 1994. On this basis, the DA/DAPIregions in the chromosomes of specimens living at 1800m (Fig.…”

Cytogenetics and biogeography: considerations about the natural origin of Hoplias malabaricus (Characiformes, Erythrinidae) on the Iguaçu river

“…This heterochromatin was not found to be related to NORs in the western population, which might represent an exception feature amongst fishes (Souza et al, 1996;Artoni et al, 1999;Margarido and Galetti Jr., 2000). Indeed, GC-rich heterochromatin associated with NORs is a common character in fish species (Mayr et al, 1985;Schmid and Guttenbach, 1988;Phillips and Hartley, 1988;Sola et al, 1992). The location of this heterochromatin in distinct chromosome pairs, besides its relation with NOR only in the eastern population, are good evidences that a karyotypic diversification have already occurred at some degree between the populations.…”