Chromosome Mapping of Repetitive Sequences in Rachycentron canadum (Perciformes: Rachycentridae): Implications for Karyotypic Evolution and Perspectives for Biotechnological Uses

Abstract

The cobia, Rachycentron canadum, a species of marine fish, has been increasingly used in aquaculture worldwide. It is the only member of the family Rachycentridae (Perciformes) showing wide geographic distribution and phylogenetic patterns still not fully understood. In this study, the species was cytogenetically analyzed by different methodologies, including Ag-NOR and chromomycin A3 (CMA3)/DAPI staining, C-banding, early replication banding (RGB), and in situ fluorescent hybridization with probes for 18S and 5S ribosomal genes and for telomeric sequences (TTAGGG)n. The results obtained allow a detailed chromosomal characterization of the Atlantic population. The chromosome diversification found in the karyotype of the cobia is apparently related to pericentric inversions, the main mechanism associated to the karyotypic evolution of Perciformes. The differential heterochromatin replication patterns found were in part associated to functional genes. Despite maintaining conservative chromosomal characteristics in relation to the basal pattern established for Perciformes, some chromosome pairs in the analyzed population exhibit markers that may be important for cytotaxonomic, population, and biodiversity studies as well as for monitoring the species in question.

Unusual Dispersion of Histone Repeats on the Whole Chromosomal Complement and Their Colocalization with Ribosomal Genes in <b><i>Rachycentron canadum</i></b> (Rachycentridae, Perciformes)

“…These rearrangements are predominant evolutionary events in representatives of marine fish groups, such as Pomacentridae, Carangidae, and Apogonidae [Molina and Galetti, 2004;Rodrigues et al, 2007;Araújo et al, 2010], and are considered one of the primary mechanisms of chromosomal diversification in Perciformes fishes [Galetti et al, 2000[Galetti et al, , 2006. The occurrence of Ag-NOR/18S and 5S sites in some bi-armed pairs may suggest that ribosomal genes have taken part in the diversification process of these chromosomes, as suggested for other species of marine Perciformes fishes [Molina and Galetti, 2002;Affonso and Galetti, 2005;Jacobina et al, 2011].…”

Chromosomal distribution of two multigene families and the unusual occurrence of an X1X1X2X2/X1X2Y sex chromosome system in the dolphinfish (Coryphaenidae): An evolutionary perspective

“…Mapping data of the ribosomal subunit 5S in Carangoidei remains scarce. In C. hippurus and C. equiselis, these sequences are also simple and invariant, and are exclusively conserved on the smallest chromosome pair (24), which is in direct contrast to the presence of two 5S sites in the only representative of the Rachycentridae family that has been analyzed (Jacobina et al, 2011). In many vertebrates, such as Coryphaenidae, 5S rDNA genes are located on a single chromosome pair; however, in fish, these genes may be found on just one pair or several chromosomes (Mazzei et al, 2004).…”

“…However, despite this relative conservation, it is important to underscore the differentiation of the X 1 X 2 Y system in C. equiselis, which represents a derived characteristic when compared to other species of large pelagic Perciformes. It is worth highlighting that in Rachycentron canadum, a monotypic species belonging to the Rachycentridae family, which forms a monophyletic group with Coryphaenidae (Gray et al, 2009), there is no evidence of differentiated sex chromosomes (Jacobina et al, 2011). Hence, it might be possible to extend the present study on C. hippurus males to determine whether differentiated sex chromosomes are present in this species; therefore, this study might potentially contribute towards characterizing synapomorphy in the Coryphaenidae family, or the exclusive autapomorphy of C. equiselis, as well as providing possible implications of this sex chromosome system for the speciation in this group.…”

Telomeres in Fishes

“…Among actinopterygians, chromosomal location of the telomeric DNA repeats has been examined in the Chondrostei species from 2 orders: Acipenseriformes [Fontana et al, 1998[Fontana et al, , 2004[Fontana et al, , 2008 and Polypteriformes [Moreschalchi et al, 2007[Moreschalchi et al, , 2008. Within ray-finned fish of the infraclass Teleostei, the chromosomal distribution of the telomeric DNA sequences has been studied in fish species belonging to 15 orders: Anguilliformes [Salvadori et al, 1995], Batrachoidoformes [Merlo et al, 2007], Characiformes [de Marco Ferro et al, 2003;, Cypriniformes [Meyne et al, 1990;Gornung et al, 1998;Sola et al, 2003a;Ocalewicz et al, 2004a;Gromicho et al, 2006;Schmid et al, 2006], Gasterosteiformes [Ocalewicz et al, 2011], Gymnotiformes [Milhomem et al, 2008;Silva et al, 2009;Felippe and Foresti, 2010;Scacchetti et al, 2011], Mugiliformes [Gornung et al, 2004;Rossi et al, 2005], Osmeriformes , Perciformes [Mandrioli et al, 2000;Sola et al, 2000Sola et al, , 2003bChew et al, 2002;Molina and Galetti, 2002;Mota-Velasco et al, 2010;Wang et al, 2010;Jacobina et al, 2011;Ocalewicz and Sapota, 2011;Jankun et al, 2013], Pleuronectiformes [Cross et al, 2006;Ocalewicz et al, 2008a], Salmoniformes [Reed and Phillips, 1995;Abuin et al, 1996;…”