Association of nucleolus organizer chromosomes shown by silver staining in Gobius fallax

Karyotype analysis, nucleolus organizer regions and C-banding pattern of Eisenia foetida (oligochaeta, lumbricidae)

“…The highest number of nucleoli per nucleus corresponds to the actual number of chromosomes involved in the nucleolus organization. This condition is very similar to that observed in fish (Thode et al, 1983;Vitturi & Catalano, in press) and molluscan species (Goldman et al, 1983;Vitturi & Catalano, 1989), where the maximum number of nucleoli and the number of NORs at mitotic metaphase agree well. According to the current interpretation (Miller et al, 1976;Hubbel et al, 1980;Hernandez-Verdun et al, 1982;Fakan & HernandezVerdun, 1986), the smaller sizes of the NORs of the diakinetic bivalent at metaphase-!…”

A complex chromosomal polymorphism in Gobius fallax (Gobiidae, Perciformes)

“…This situation was also observed in one individual that does not belong to the sample and in which some metaphase plates stained with silver nitrate showed an acrocentric chromosome fused to one of the four chromosomes (Fig. 4) already characterized as bearing the NOR's (Thode et al, 1983b). Hence the question arises as to the nature of these chromosome fusions: do true fusions occur among the same homologous pairs or are they randomly produced among chromosomes of more than two different pairs?…”

“…In the present paper we have renewed our investigation of chromosomal polymorphism in Gobiusfallax Sarato, 1889, a species in which mosaicism for the diploid number (2n = 40-42) due to a Robertsonian translocation had been previously observed. This variation, affecting about ten percent or less of the cells in each individual, involved the two acrocentric pairs bearing the NORs (Thode et al, 1983b).…”

Conservative nature of the Nucleolus Organizer Region in three species of Mediterranean Mugilids

“…Other stain techniques will have to be applied for its verification, but we believe that this situation may also occur in other karyotypes (as f.e. in THODE et al 1983). In any case, only one pair of NORs is representative in these three mugilid species, since the second pair is expressed in a very low proportion ( < 5%).…”