Histology of the gonads of the hybrid Pseudoplatystoma punctifer X Leiarius marmoratu

Abstract

Considering the rapid expansion of fish farming in intensive systems and the use of hybrids in Brazil, the study regarding the breeding capacity of the most recent hybrid is of ecological importance. If these animals are fertile, they may breed with the parental species in the wild and can negatively affect the genetic variability of the population (parental species in the wild). Fragments of the gonads were collected and submitted to histological evaluation. Histological cuts were stained with eosin/hematoxylin and toluidine, and slides were randomly selected for observation of three fields of each animal, through light microscopy. Gonads of all fishes were paired structures of elongated shape in the abdominal cavity, covered by an albuginea tunic. Male juveniles presented primary spermatocytes while juvenile females presented chromatin nucleolus oocytes. Adult females presented chromatin-nucleolus oocytes, perinuclear, cortical alveoli, and vitelogenic oocytes visible in various sizes. The presence of oocytes in different stages and primary spermatocytes indicate that these fish may be fertile. Fish hybridization represents a threat to the conservation of native species.