Abstract
ABSTRACT Monitoring of the interspecific hybrid production and trade is essential for the appropriate management of these animals in fish farms. The identification of catfish hybrids by morphological analysis is unreliable, particularly of juveniles and post-F1 individuals. Therefore, in the present study, we used five molecular markers (four nuclear genes and one mitochondrial gene) to detect hybrids in the trade of pimelodid juvenile fish from different stocks purchased of five seed producers in Brazil. Samples commercialized as pintado (pure species Pseudoplatystoma corruscans ) from three fish farms were genetically identified as hybrid cachapinta (♀ P. reticulatum x ♂ P. corruscans ). In the stocks purchased as cachandiá (hybrid between ♀ P. reticulatum x ♂ Leiarius marmoratus ) and cachapira (hybrid between ♀ P. reticulatum x ♂ Phractocephalus hemioliopterus ), we suggested the occurrence of intergenus crosses involving the hybrid cachapinta, which was used instead of the pure species P. reticulatum . The problems involving the hybrid cachapinta production were discussed in the present study, especially because these animals have caused genetic contamination and threatened the genetic integrity of natural and cultivated populations. In order to improve the surveillance of the production and provide criteria for the correct management of catfish hybrids, genetic markers has become an excellent alternative to the morphological identification, including juveniles or post-F1 generations.
Highlights
The artificial production of interspecific hybrids consists in a classical method of genetic improvement for aquaculture programs
Through multiplex-PCR of the mitochondrial marker, these hybrids showed the genotype of the maternal species P. reticulatum, which allowed the identification of these samples as cachapinta (♀ P. reticulatum x ♂ P. corruscans) instead the reciprocal hybrid pintachara (♀ P. corruscans x ♂ P. reticulatum)
Through multiplex-PCR of the rag2 gene, we observed two distinct electrophoresis patterns in the individuals purchased as hybrid cachandiá: 19 samples were identified with a heterozygous genotype scored for hybrids between P. reticulatum and L. marmoratus; 22 samples revealed a heterozygous pattern, but characterized for hybrids between P. corruscans and L. marmoratus (Table 3)
Summary
The artificial production of interspecific hybrids consists in a classical method of genetic improvement for aquaculture programs. This technique is widely used for several catfish species of commercial importance, especially in Brazil where about 20 native catfish have been cultivated in aquaculture (Bartley et al, 2001; Hashimoto et al, 2012; Moro et al, 2013). Hybridization programs have currently involved fish from other genera, such as Leiarius marmoratus (Gill 1870) (jundiá amazônico) and Phractocephalus hemioliopterus (Bloch & Schneider 1801) (pirarara), aiming to produce differentiated products and solve problems associated with feeding and cannibalism that can be observed in the early stages of development of these species (Campos, 2010; Porto-Foresti et al, 2010,2013). P. reticulatum has a longer reproductive period and it is the species most used by the fish farmers as the female parental to generate the interspecific hybrids, named cachapinta (crossed with P. corruscans), cachandiá (crossed with L. marmoratus) and cachapira (crossed with P. hemioliopterus) (Campos, 2010; Porto-Foresti et al, 2010, 2013)
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