Abstract
This study reports the description of the karyotype of Mugil incilis from Venezuela. The chromosome complement is composed of 48 acrocentric chromosomes, which uniformly decrease in size. Therefore, the homologues can not be clearly identified, with the exception of one of the largest chromosome pairs, classified as number 1, whose homologues may show a subcentromeric secondary constriction, and of chromosome pair number 24, which is considerably smaller than the others. C-banding showed heterochromatic blocks at the centromeric/pericentromeric regions of all chromosomes, which were more conspicuous on chromosomes 1, given the C-positive signals include the secondary constrictions. AgNO3 and fluorescent in situ hybridization (FISH) with 45S rDNA demonstrated that the nucleolus organizer regions are indeed located on the secondary constrictions of chromosome pair number 1. FISH with 5S rDNA revealed that the minor ribosomal genes are located on this same chromosome pair, near the NORs, though signals are closer to the centromeres and of smaller size, compared to those of the major ribosomal gene clusters. This is the first description of co-localization of major and minor ribosomal genes in the family. Data are discussed from a cytotaxonomic and phylogenetic perspective.
Highlights
The fish family Mugilidae is composed of approximately 70 species and it inhabits coastal and brackish waters of all tropical and temperate regions of the world (Thomson, 1997; Froese & Pauly, 2010)
According to Cervigón (1993), in Venezuela the family Mugilidae is represented by six mullet species, four of which, Mugil curema, M. rubrioculus, M. liza, M. trichodon, have already been cytogenetically investigated
This paper reports the chromosome number and formula, constitutive heterochromatin distribution by C-banding and the locations of major and minor ribosomal genes by Ag-staining and Fluorescent in situ Hybridization (FISH) in M. incilis
Summary
The fish family Mugilidae (mullets) is composed of approximately 70 species and it inhabits coastal and brackish waters of all tropical and temperate regions of the world (Thomson, 1997; Froese & Pauly, 2010). Recent cytogenetic studies carried out on several Mugilidae species from Venezuela (reviewed in Sola et al, 2007, 2008) have provided information regarding several interesting systematic and cytotaxonomic issues within the family. This study was carried out to continue the karyological characterization of Venezuelan mugilids, presenting cytogenetic data of the parassi mullet, Mugil incilis. This species lives in brackish estuaries and in the marine and hyper-saline waters (Cervigón et al, 1992) of the Western Atlantic from the West Indies and the Atlantic coasts of Central America southward to Brazil (Froese & Pauly, 2010). The images were acquired using a SenSys 1400 CCD camera and artificially coloured and elaborated with Photoshop CS3 (Adobe Systems Inc)
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