Search

Genetic diversity and structure of Pseudoplatystoma corruscans and P. reticulatum, large migratory South America catfishes, where overfishing and the construction of numerous dams in their feeding and reproducing areas are affecting their migratory processes negatively, were studied using microsatellites in samples from Paraguay (that comprises the Pantanal biome), and the upper and lower Paraná Basins. Genetic diversity was in accordance to that observed for other large migratory fishes, but the most geographically isolated populations of P. reticulatum and those P. corruscans subject to anthropogenic effects (stocking and dams) showed lower genetic diversity and evidences of bottlenecks compatible with low effective population size. Pseudoplatystoma reticulatum presented subtle genetic differentiation within the Paraguay area, especially between the edges of its distribution. Pseudoplatystoma corruscans, in this same area, presented a quite homogeneous but significant genetic break between the Paraguay and upper Paraná populations, apparently resulting from natural and historical isolation between the basins until recently. These data demonstrates that, although these Pseudoplatystoma spp. are abundant in the Pantanal area, anthropogenic events are leading to negative effects on their populations, particularly in the upper Paraná Basin. Genetic differentiation observed along each species distribution demands conservation actions to preserve each population's biodiversity. These results represent important genetic information using new microsatellite markers and the first genetic study of P. reticulatum covering this area of its native distribution. Data may also contribute to a better understanding of species migration patterns and to be used as a baseline for proper management. [ABSTRACT FROM AUTHOR]

This study evaluated the efficiency of differently prepared vaccines against Aeromonas hydrophila in the hybrid surubim ( Pseudoplatystoma corruscans × P. reticulatum). Survival and haemato-immunological parameters were compared between the treatments: non-vaccinated fish (C); bacterin-vaccinated fish (B); bacterin plus oral booster vaccinated fish (B+O); bacterin and toxoid-vaccinated fish (B+T) and bacterin, toxoid and oral booster-vaccinated fish (B+T+O). Fourteen-days vaccinated fish from B+O and B+T+O were fed with an oral booster for 4 days. After 1 week, the fish were intraperitoneally challenged with 2 × 108 CFU mL−1 of A. hydrophila. Fish from the treatment B+T+O showed the lowest cumulative mortality (11.36%) 96 h after challenge, compared with other treatments (22.72-44.04%), and a relative survival of 74%. Serum immunoglobulin in B+T+O fish was higher than in other treatments. All vaccinated fish showed an increased agglutination titre when compared with non-vaccinated fish, both before and after challenge. Fish fed with oral booster showed an increase in phagocytic percentage before and after challenge. It can be inferred that the oral booster vaccination was efficient in reducing mortality in hybrid surubim by enhancing the response against haemorrhagic septicaemia due to A. hydrophila infection. [ABSTRACT FROM AUTHOR]

The article discusses a study that presents the first record of early gender coelioscopy of surubim hybrids Pseudoplatystoma corruscans x Pseudoplatystoma reticulatum. It states that a total of 113 surubim hybrids were analysed. Moreover, the study concludes that coelioscopy is a reliable technique to identify the gender of female surubim hybrids during the early developmental stages.

Herein, we have developed molecular markers for nuclear genes to use in multiplex- PCR and PCR- RFLP, with the goal of characterising hybrid lines derived from crosses between pintado Pseudoplatystoma corruscans and cachara P. reticulatum. These markers, together with others described previously, were used to perform molecular identification analyses as genetic subsidies for Brazilian aquaculture. These analyses were performed due to the problems of high mortality in the offspring reported by the aquaculturist. From a total of 16 broodstock samples, 13 were genetically identified as hybrids; surprisingly, nine of these hybrids were found to be post-F1 lineages. These data show that the fertility of these animals can seriously affect the cultivated stocks, thus causing financial damage in this aquaculture system. The establishment of PCR- RFLP and multiplex- PCR as molecular techniques allows for both the correct management of these animals and the routine monitoring of production and trade of fish hybrids in aquaculture. Consequently, such tools will enable a sustainable development in the aquaculture industry. [ABSTRACT FROM AUTHOR]