Histomorphologic study and analysis of the cellular profiles of the head kidney, liver, spleen and thymus of Piaractus mesopotamicus (Holmberg, 1887, Teleostei, Characidae), pacu

Author(s)

Gerlane de Medeiros Costa

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD)
• Defense date: 2007-12-11

Examining board members

José Roberto Kfoury Junior; Ana Flávia de Carvalho; Paula de Carvalho Papa

• Advisor: José Roberto Kfoury Junior

Abstract

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, eosinophils and special granulocytic cells were found in peripheral blood of both juvenile and adult animals and were similar to the cellular profiles described in the literature to the other teleost fishes. Our studies were successful in describing the macro, micro and ultrastructure of Piaractus mesopotamicus organs and may be used as reference for further research aiming the improvement of fish health status in aquaculture. (AU)