We investigated the occurrence and ultrastructurally characterized electrondense nuclear material (nuage) released from the nucleus during oogenesis and early spermatogenesis of Piaractus mesopotamicus, a fish from Pantanal Matogrossense (Brazil) having a seasonal reproductive cycle. The female germ cells presented two instances of nuclear material extrusion: in the oogonia and in the oocyte in...

Anacanthorus penilabiatus is referred parasitizing the type-host Piaractus mesopotamicus (Serrasalmidae) and two new hosts, Colossoma macropomum and C. brachypomum (Characidae) from fish ponds of "Departamento Nacional de Obras Contra as Secas", Pentecoste, State of Ceará, Brazil. Table of measurements and the first description of the egg are presented.

Measurement of blood parameters has been used for many years as a tool for monitoring the health of fish. The present study investigated the effects of a natural infestation of Dolops carvalhoi Lemos de Castro, 1949, on red blood cells, thrombocytes and white blood cell counts, as well as plasma glucose and serum electrolyte levels in hybrid tambacu (Piaractus mesopotamicus x Colossoma macropom...

Juvenile fish trade monitoring is an important task on Brazilian fish farms. However, the identification of juvenile fish through morphological analysis is not feasible, particularly between interspecific hybrids and pure species individuals, making the monitoring of these individuals difficult. Hybrids can be erroneously identified as pure species in breeding facilities, which might reduce pro...

This paper describes various aspects of oogenesis in Piaractus mesopotamicus (pacu), particularly the changes in nuclear morphology and the nuclear-cytoplasmic interactions during the early developmental stages of oocytes. Material produced in the nucleus and passed to the cytoplasm, known as “nuage”, was observed in oogonia and in oocytes. In the oocyte cytoplasm, this material gives rise to g...

The Serrasalmidae family is composed of a number of commercially interesting species, mainly in the Amazon region where most of these fishes occur. In the present study, we investigated the genomic organization of the 18S and 5S rDNA and telomeric sequences in mitotic chromosomes of four species from the basal clade of the Serrasalmidae family: Colossoma macropomum, Mylossoma aureum, M. duriven...

This study evaluated the occurrence of parasitic infections in the "pacu" fish Piaractus mesopotamicus and the "patinga" hybrid (P. mesopotamicus x Piaractus brachypomus) in the northwest of São Paulo State, Brazil. Fish from the following three fish farms were evaluated every two months: A, a hatchery and larviculture farm (n = 16 pacu / n = 19 patinga), B, a growout farm (n = 35 patinga) and ...

The aim of this study was to determine the environmental concentration of atrazine (ATZ) in five streams located in the north of São Paulo state (Brazil) and evaluate its toxicological impact on young specimens of the pacu fish Piaractus mesopotamicus. Samples of water were collected on three occasions between 2010 and 2011, corresponding to periods signifying the beginning, middle, and end of ...