10
ABSTRACT
COSTA, G. M. Histomorphologic study and analysis of the cellular profiles of
the head kidney, liver, spleen and thymus of Piaractus mesopotamicus
(Holmberg, 1887, Teleostei, Characidae), pacu. [Estudo histomorfológico e análise
dos perfis celulares do rim cefálico, fígado, baço e timo do Piaractus mesopotamicus
(Holmberg, 1887, Teleósteo, Characidae), pacu.]. 2007. 133 f. Dissertação (Mestrado
em Ciências) – Faculdade de Medicina Veterinária e Zootecnia, Universidade de São
Paulo, São Paulo, 2007.
Piaractus mesopotamicus (Pacu) is a fish from the Characidae Family, it is
intensively culture in Brazil because of its rusticity, easy raising and adaptation,
besides its excellent flavour. In order to produce a healthy fish, information on its
immunological system, including the histology of the lymphoid organs is needed.
Therefore, the objective of this study is to describe histomorphologicaly the lymphoid
organs: head kidney, liver, spleen and thymus of the Piaractus mesopotamicus,
analyzing the cellular profiles of each organ. Thirty young animals, with age varying
between 5 months to a year, with average weight and total length of 588.1 g and a
27.51 cm, respectively, were used. The organs were fixed in 4% paraformaldehyde
solution, and Karnovsky, afterwards dehydrated, diafanized in xilol and included in
paraffin. Four µm sections were obtained and stained with hematoxilin-eosin. Blood
smears were stained with Giemsa-May Grünwald for light microscopy. Samples for
transmission electric microscopy were fixed in Karnovsky, washed in sacarose and
post-fixed with osmium tetroxide 1%, dehydrated and embedded in resin Spurr. The
macroscopic analysis show that the localization of the kidney, head kidney, thymus,
liver and spleen are very similar to most of the teleosts. Some particularities were
observed in the liver, which presented an anatomical variation in the shape and
number of lobes, being constituted by three lobes. The kidney presented existe "H"
shape, where the central region overlaps the swimming bladder. The head-kidney, in
adult animals, presented an evident dilation in the cranial region of the kidney. The
thymus and spleen presented a similar location and shape to that of the teleosts. The
light microscopy studies showed similarities between the organs of the Piaractus
mesopotamicus and other teleost fishes. The transmission electron microscopy
studies showed ultrastructural similarities, of the cells from the head kidney, liver,
thymus and spleen with the literature. Eritrocytes, trombocytes, lymphocytes,