Abstract
The Erythrinidae family (Teleostei: Characiformes) is a small Neotropical fish group with a wide distribution throughout South America, where Hoplias malabaricus corresponds to the most widespread and cytogenetically studied taxon. This species possesses significant genetic variation, as well as huge karyotype diversity among populations, as reflected by its seven major karyotype forms (i.e., karyomorphs A-G) identified up to now. Although morphological differences in their bodies are not outstanding, H. malabaricus karyomorphs are easily identified by differences in 2n, morphology and size of chromosomes, as well as by distinct evolutionary steps of sex chromosomes development. Here, we performed comparative genomic hybridization (CGH) to analyse both the intra- and inter-genomic status in terms of repetitive DNA divergence among all but one (E) H. malabaricus karyomorphs. Our results indicated that they have close relationships, but with evolutionary divergences among their genomes, yielding a range of non-overlapping karyomorph-specific signals. Besides, male-specific regions were uncovered on the sex chromosomes, confirming their differential evolutionary trajectories. In conclusion, the hypothesis that H. malabaricus karyomorphs are result of speciation events was strengthened.
Highlights
The Erythrinidae family (Teleostei: Characiformes) is a small group of Neotropical fishes with a wide distribution throughout South America
The total genomic DNAs from male and female specimens of all karyomorphs listed in Table 1 were extracted from liver tissue by the standard phenol-chloroformisoamylalkohol method (Sambrook and Russell, 2001)
Similar situation was observed in karyomorph C (Figures 2E–H), where the majority of the accumulated blocks was shared by both probes, including those in the pericentromeric regions of the XY chromosomes, but several signals and especially those located in the terminal region of the long arms of the largest m pair were found to be accumulated with C-specific probe only
Summary
The Erythrinidae family (Teleostei: Characiformes) is a small group of Neotropical fishes with a wide distribution throughout South America. This family currently consists of three well-recognized genera—Erythrinus (Scopoli, 1777), Hoplias (Gill, 1903), and Hoplerythrinus (Gill, 1895) with at least 15 until now recognized species (Oyakawa, 2003; Oyakawa and Mattox, 2009). Unlike the large migratory Neotropical fishes, they are usually not able to overcome obstacles such as waterfalls and large rapids, due to their sedentary lifestyle (Oyakawa, 2003). This situation may have contributed to reduced gene flow between sub-populations in the same hydrographic basin. Great genome diversity has been documented within the Genomic Divergence in Hoplias malabaricus
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