Karyotype variability in neotropical catfishes of the family Pimelodidae (Teleostei: Siluriformes)

Abstract

Karyotypic data are presented for four species of fish belonging to the Pimelodidae family. These species show a conserved diploid number, 2n = 56 chromosomes, with different karyotypic formulae. The analyzed species showed little amount of heterochromatin located preferentially in the centromeric and telomeric regions of some chromosomes. The nucleolus organizer regions activity (Ag-NORs) and the chromosomal location of ribosomal genes by fluorescent in situ hybridization (FISH), with 18S and 5S probes, showing only one chromosome pair marked bearer of ribosomal genes, the only exception was Pimelodus britskii that presented multiple NORs and syntenic location of the 18S and 5S probes. Non-Robertsonian events, as pericentric inversion and NORs duplication are requested to explain the karyotype diversification in Pseudoplatystoma from the rio Paraguay (MS), Pimelodus from the rio Iguaçu (PR), Sorubim from the rio Paraguay (MS) and Steindachneridion from the rio Paraíba do Sul (SP). The obtained data for the karyotype macrostructure of these species corroborates a conserved pattern observed in Pimelodidae. On the other hand, interspecific variations detected by molecular cytogenetics markers made possible cytotaxonomic inferences and differentiation of the species here analyzed.Dados cariotípicos são apresentados para quatro espécies da família Pimelodidae. Todas apresentaram o mesmo número diploide, 2n = 56 cromossomos, com diferenças nas fórmulas cariotípicas. As espécies aqui analisadas mostraram pouca quantidade de heterocromatina localizada preferencialmente na região centromérica e telomérica de alguns cromossosmos do complemento cariotípico. As regiões organizadoras de nucléolo (Ag-RONs) e a localização dos genes ribossomais pela hibridização in situ fluorescente (FISH), com sondas 18S e 5S, evidenciaram somente um par cromossômico marcado portador de genes ribossomais, à exceção de Pimelodus britskii que apresentou NORs múltiplas e localização sintênica das sondas 18S e 5S. Eventos não-Robertsonianos, como inversão pericêntrica e duplicação das NORs são requeridos para explicar a diversificação cariotípica em Pseudoplatystoma do rio Paraguai (MS), Pimelodus do rio Iguaçu (PR), Sorubim do rio Paraguai (MS) e Steindachneridion do rio Paraíba do Sul (SP). Os dados obtidos para a macroestrutura cariotípica destas espécies corrobora um padrão conservado observado na família Pimelodidae. Por outro lado, evidências de variações interespecíficas pelos marcadores de citogenética molecular empregados possibilitam inferências citotaxonômicas e diferenciação das espécies aqui analisadas.

Karyotypic conservatism in five species of Prochilodus (Characiformes, Prochilodontidae) disclosed by cytogenetic markers

“…In addition to P. lineatus (Jesus and Moreira-Filho, 2003; Vicari et al , 2006; Voltolin et al , 2009), this synteny was also observed in Salmo salar (Pendás et al , 1994), Oncorhynchus mykiss (Móran et al , 1996), Astyanax (Almeida-Toledo et al , 2002), in amphibians (Lucchini et al , 1993) and, more recently, in Pimelodus britskii (Moraes-Neto et al , 2011). On the other hand, these loci have been mapped on different chromosomes in many fish species (Martinez et al , 1996; Morán et al , 1996; Born and Bertollo , 2000 ; Ferro et al , 2001; Vicente et al , 2001; Wasko et al , 2001; Noleto et al , 2007), representing the most frequent condition in vertebrates (Lucchini et al , 1993; Drouin and Muniz De Sá, 1995, Suzuki et al , 1996).…”

Chromosomal diversity in Hypostomus (Siluriformes, Loricariidae) with emphasis on physical mapping of 18S and 5S rDNA sites

“…Gene conversion and unequal crossing mechanisms are likely to occur in 18S and 5S rDNA sites with syntenic arrangements; thus, the location of these genes on different chromosomes avoids possible unfavorable rearrangements (Dover, 1986). However, several groups of Neotropical fish carry the major and minor ribosomal genes in the same chromosome in an adjacent, distant or co-located position (Hatanaka and Galetti Jr., 2004;Moraes-Neto et al, 2011). The synteny between ribosomal genes in metacentric/submetacentric pairs observed in H. ancistroides and H. tapijara is the first report of this condition in the genus.…”

First chromosome data on Steindachneridion doceanum (Siluriformes: Pimelodidae): a critically endangered catfish endemic of the Doce River basin, Brazil

“…Cytogenetic studies on Steindachneridion are available for S. scriptum (Swarça et al, 2005a), S. melanodermatum (= Steindachneridion sp.) (Swarça et al, 2006) and S. parahybae (Moraes-Neto et al, 2011) and despite sharing some chromosomal similarities, cytogenetic traits of the S. doceanum (present paper) such as karyotypic formula, Ag-NORS and C-banding patterns were divergent (Tab. 1).…”

“…Three species of the genus were previously studied cytogenetically, Steindachneridion scriptum (Swarça et al, 2005a), S. melanodermatum (= Steindachneridion sp.) (Swarça et al, 2006) and S. parahybae (Moraes-Neto et al, 2011). The aim of the present study was to characterize S. doceanum at the karyotypic level by means of standard and fluorescent in situ hybridization techniques comparing the obtained data with these from other Steindachneridion species.…”