Abstract
The genetic monitoring of interspecific hybrids involves the application of methodologies able to provide an easy and indubitable genetic characterization of both parental and hybrid individuals. In the present work, cytogenetic techniques were used to identify a hybrid lineage of Piaupara in order to caracterize them in relation to the parental species, Leporinus macrocephalus (piaucu) and L. elongatus (piapara). The cytogenetic analysis revealed that L. macrocephalus presented 2n = 54 chromosomes and a nucleolar organizer regions (NOR) at the telomere of the long arm of the submetacentric chromosome pair 2. Analysis of constitutive heterochromatin (C-banding) revealed a conspicuous block at the pericentromeric region on the long arm of a submetacentric chromosome pair. L. elongatus presented the same diploid number, 2n = 54, and a karyotypic formula similar to that of L. macrocephalus. The NORs were also at the telomere of the long arm of the submetacentric pair 2, which was morphologically different from that of L. macrocephalus. Heterochromatic blocks were observed at both telomeres of a submetacentric chromosome pair. The hybrid Piaupara presented the same diploid number (2n = 54) and karyotypic formula as the parental species and there were no visible differences between parental and hybrid individuals. Differently from the Giemsa staining, NOR- and C-banding analysis showed marked differences which allowed the identification of the hybrids by the different morphology and/or size of the chromosomes carrying the NORs and patterns of heterochromatin distribution in their chromosomes. Such genetic studies are important for fish culture since they can provide tools for monitoring natural and artificial hybridization. They are also useful in biological conservation programmes and in the proper management of natural and reared fish stocks.
Highlights
Biological sciences and, biotechnological studies have played a major role on the development of fish culture over the last decades
Interspecific hybridization focused on productivity increase and formation of sterile lineages represents one of the main classic methods of genetic manipulation applied in fish farms
The study of interspecific hybrids depended on the cytogenetic identification of the parental species Piauçu (Leporinus macrocephalus) and Piapara (L. elongatus), chromosome preparations both species were obtained
Summary
Biological sciences and, biotechnological studies have played a major role on the development of fish culture over the last decades. The improvement of current methodologies and its application in studies of fish biology and genetics are necessary to develop a better genetic management of both captive stocks and natural populations (Porto-Foresti and Foresti, 2004). The use of artificial hybridization in fish was initiated about 30 years ago in Brazil by the Departamento de Obras Contra a Seca (DNOCS) and involved different species of tilapias (Toledo-Filho et al, 1998). Nowadays, it involves a large number of interspecific crosses among Neotropical
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