Cytogenetic analysis of global populations of Mugil cephalus (striped mullet) by different staining techniques and fluorescent in situ hybridization

Abstract

The present paper reports the results of cytogenetic analysis carried out on several scattered populations of the striped mullet, Mugil cephalus, the most widespead among mugilid species. The karyotype was investigated through Ag-staining, C-banding, fluorochrome-staining (chromomycin A3/DAPI) and fluorescent in situ hybridization with rDNA genes. All populations showed the same chromosome number and morphology and no changes were detected in heterochromatin and NORs. Therefore, neither population-nor sex-specific marker chromosomes were identified. In some of the specimens, NOR size heteromorphism was detected. Results are discussed with respect to karyotype and ribosomal cistrons organization and to cytotaxonomic implications.

Evidence of the differentiated structural arrangement of constitutive heterochromatin between two populations of Astyanax scabripinnis (Pisces, Characidae)

“…A similar lack of response of the pericentromeric heterochromatic domain after base-specific fluorochrome staining as that observed in the two populations studied by us has also been found in the chromosomes of other fish species (Sola et al, 1992;Rossi et al, 1996;Sola et al, 2000) and of other A. scabripinnis populations (Souza and Moreira-Filho, 1995;Souza et al, 1996). Considering the common pattern displayed by the A. scabripinnis populations studied to date, it may be that pericentromeric heterochromatins contain sequences with preserved compositions (seen in several species of the family Sparidae, see Garrido-Ramos et al, 1995) and preserved structures, since pericentromeric heterochromatin plays a fundamental role in the centromeric structure (Haaf et al, 1992).…”

Karyological characterization of <i>Mugil trichodon</i> Poey, 1876 (Pisces: Mugilidae)

“…It has already been hypothesized that Liza and Chelon karyotypes are derived from translocation events that affect the acrocentric ancestral chromosome complement found in Mugil, which involves NORs (Rossi et al, 1996). Our data combined with the preceding information support the hypothesis that structural chromosome rearrangements involving active NOR sites are the main cause of the karyotypic diversification seen in mugilids.…”

“…The chromosome pair characterized by a secondary constriction showed heterochromatic short arms (Fig 2D). This mostly pericentromeric location of heterochromatin was also reported in Mugil platanus (Jordao et al, 1992), M. cephalus (Rossi et al, 1996), M. liza (Nirchio, unpublished data), Liza ramada (Rossi et al, 1996), L. aurata, Chelon labrosus (Delgado et al, 1990), and O. labeo (Rossi et al, 2000).…”

“…Karyological information about the Mugilidae shows that NORs are located: on the telomeric region of the long arm of acrocen-tric chromosome pair N°1 in M. cephalus (Rossi et al, 1996), M. platanus (Jordao et al, 1992), and M. liza (Nirchio et al, 2001); on the telomeric region of the long arm of the metacentric chromosome pair N°1 in M. curema from Venezuela (Nirchio et al, 2001); on the telomeric region of the short arm of the subtelocentric chromosome pair N°11 in M. curema from Brazil (Nirchio et al, 2005); and on the short arm of the unique submetacentric chromosome pair (N°24) of Liza aurata, L. ramada, L. saliens and Chelon labrosus (Rossi et al, 1997;Gornung et al, 2001). In Oedalechilus labeo, one pair of NORs that are strikingly different in size is located on the short arms of the only subtelocentric pair (N°9); although there can be an additional, though inactive NOR, in the chromosome complement (Rossi et al, 2000).…”

Cytogenetical and morphological features reveal significant differences among Venezuelan and Brazilian samples of Mugil curema (Teleostei: Mugilidae)

“…The terminal position of NORs on the largest pair of acrocentric chromosomes has been suggested to be the plesiomorphic condition in the genus Mugil, a feature shared by M. cephalus (Rossi et al, 1996), M. platanus (Jordão et al, 1992) and M. liza (Nirchio et al, 2001;Rossi et al, 2004), but not by M. trichodon, which possesses the only interstitial NORs observed in Mugilidae . Rossi et al (2004) have proposed that the NOR pattern of of M. curema from Venezuela (Cytotype 2) would reflect the involvement of the largest ancestral NOR-bearing acrocentric chromosome in the centric fusion that produced the metacentric pair number 1 in the species.…”