Search results for "Nucleolus Organizer Region"
showing 10 items of 20 documents
Conventional karyotype, nucleolar organizer regions and genome size in five Mediterranean species of Syngnathidae (Pisces, Syngnathiformes)
1998
Conventional karyotypes, NOR-bearing chromosomes by means of silver impregnation and genome size were investigated in five Mediterranean species in three genera of the Syngnathidae. A karyotype of 48 subtelocentric-acrocentric chromosomes was found in the seahorse Hippocampus hippocampus (FN=48) while a diploid value of 44 occurred in H. guttulatus (2 sm-m+42 a; FN=46) and the pipefish Syngnathus abaster (44 a; FN=44) and S. typhle (44 a; FN=44). The pipefish Nerophis ophidion, possessing a diploid chromosomal set of 58 made up of 50 meta-submetacentric and eight subteloacrocentric elements (FN=108) and a genome size three to four times larger than those known to date, differs cytogenetical…
Karyotype analyses reveal inter-individual polymorphism and association of nucleolus-organizer-carrying chromosomes in Capros aper (Pisces: Zeiformes)
1992
Three different karyomorphs with 2n=46, 2n=44 and 2n=42 for Capros aper (L., 1758) (Zeiformes) collected from the Gulf of Lion, near Banyuls-sur-Mer, France, in July 1990 were determined. Karyomorphs were characterized by the same arm number [Fundamental number (FN)=50], suggesting that chromosome variations are due to Robertsonian fusions. In somatic metaphase spreads stained with silver nitrate, nucleolus organizer regions (NORs) consistently occupied a terminal position on the short arms of two small submetacentric chromosomes. Ca. 30% of silver-stained metaphases in each specimen showed NOR chromosomes associated in pairs by their nucleolus organizer regions.
Karyotype analysis, nucleolus organizer regions and C-banding pattern of Eisenia foetida (oligochaeta, lumbricidae)
1991
The diploid number 2n=22 and haploid number n=11 found for Eisenia foetida from Palermo, Italy, confirm earlier data for this species from other localities. Analyses of silver-stained and C-banded mitotic and meiotic chromosomes suggest that a single chromosome pair has active NORs which correspond with C-positive regions. The occurrence of nucleolus activity during spermatogenesis of E. foetida is ascertained.
Karyological and Molecular Characterization of Mullus surmuletus and Mullus barbatus(Pisces, Mullidae).
1992
The modal diploid number of 44 chromosomes has been found in Mullus surmuletus and Mullus barbatus (Pisces, Mullidae). Two middle-sized subtelocentric chromosomes are involved in nucleolus organization (NORs) in both Mullus species. Despite similarity in the NOR location, valuable differences in the restriction pattern of the ribosomal genes have been observed.
Spermatocyte chromosome analysis of the slugLehmannia melitensis(Lessona and Pollonera, 1891) (Mollusca, Pulmonata) using conventional, NOR- and C-ba…
1993
SUMMARYDiploid number 2n = 40 and haploid number n = 20 for the slug Lehmannia melitensis have been determined. These chromosome values being considerably different from those reported for slugs belonging to other limacid genera support the notion that the genus Lehmannia is particular within the family Limacidae. Nucleolus organizer regions (NORs) and C-banding pattern of L. melitensis are described.
Karyotype analysis of the sea urchinParacentrotus lividus (Echinodermata): evidence for a heteromorphic chromosome sex mechanism
1996
A consistent diploid number of 2n = 36 was determined for the sea urchinParacentrotus lividus from the Gulf of Palermo by analysis of mitotic chromosomes of both early developing embryos and male gonads. The haploid numbern = 18 was determined by counts of spermatocyte bivalents at diakinesis. A heteromorphic chromosome sex mechanism of the XY type is likely present in this species. This is indicated by the occurrence of a chromosomal pair, pair No. 2, which is heteromorphic in both morphology and size in about 50% of the mitotic figures (metaphases and anaphases) of einbryos. In addition, heteromorphism of the same pair of chromosomes occurred during spermatogonial metaphases in the five m…
Chromosomal nucleolar organizer region (NOR) phenotypes in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae)
1995
Chromosomal nucleolar organizer region (NOR) phenotypes have been characterized in nine species of the genus Ophryotrocha (Polychaeta: Dorvilleidae), namely O. notoglandulata, O. sp. macrovifera, O. sp. labronica pacifica, O. labronica labronica, O. puerilis puerilis, O. diadema, O. sp. robusta, O. gracills and O. hartmanni. Irrespective of chromosome number and morphology, Ag positive regions were terminally located in all but one species, O. diadema, where the NORs were pericentromerical in a metacentric pair. The presence of a single chromosome pair bearing NOR in invertebrates is considered an ancestral trait. According to this assumption, O. sp. robusta, O. dialema, and perhaps O. p. p…
Cytogenetics in the sacoglossan Oxynoe olivacea (Mollusca: Opisthobranchia): karyotype, chromosome banding and fluorescent in situ hybridization
2000
Developing embryos and sexually mature follicles of the male portion of ovotestis proved to be a suitable material as a source of cleaving cells for advanced cytological investigations on the sacoglossan species Oxynoe olivacea Rafinesque, 1819 (Mollusca: Opisthobranchia). O. olivacea has a diploid chromosomal number of 30 made up of 15 pairs of which six are metacentric/submetacentric (M/SM), four subtelocentric (ST) and five on the borderline between SM and ST. Correspondingly, 15 bivalents occur in spermatocytes at Metaphase I. Constitutive heterochromatin is scarce and restricted to small C-bands seen in five pachytene bivalents. The use of combined silver staining and fluorescent in si…
Ag-NOR and C-banding analysis of spermatocyte chromosomes ofClavelina lepadiformis(Ascidiacea, Aplousobranchiata)
1991
SUMMARYChromosome number n = 9 and 2n = 18 for Clavelina lepadiformis (Ascidiacea, Aplousobranchiata) from the Gulf of Palermo have been determined. Silver staining analysis of testicular cells reveals that within-individual variability in NOR banding patterns is present. Using the C-banding procedure, a very impressive heterochromatin amount seems to characterize the chromosome set of this species.
Brief communication. Karyotype analysis, banding, and fluorescent in situ hybridization in the scarab beetle Gymnopleurus sturmi McLeay (Coleoptera S…
2000
Conventional staining, differential banding, and in situ hybridization with both ribosomal and telomeric probes to mitotic chromosomes of Gymnopleurus sturmi (Scarabaeoidea : Scarabaeidae) are described. The karyotype is distinguished by a pericentric inversion polymorphism in chromosome 3, which is either acrocentric or subtelocentric. Silver staining (Ag-NOR) and chromomycin A3 (CMA3), failed to study the detection of nucleolar organizer regions (NORs), due to the extensive silver and CMA3 stainability of all GC-rich heterochromatin. Fluorescent in situ hybridization (FISH) using a Paracentrotus lividus (Echinodermata) rDNA probe mapped the ribosomal RNA genes (rDNA). FISH with the all-hu…