February 15-18, 2009 Washington State Convention Center Seattle ...

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ULTRASTRUCTURAL STUDY OF THE NUCLEOLAR CYCLE DURING
SPERMATOGENESIS OF Tilapia rendalli (TELEOSTEI, CICHLIDAE)
Rita L. Peruquetti * , Sebastião R. Taboga and Maria Tercília V. Azeredo-Oliveira
São Paulo State University
Departmento of Biology
São José do Rio Preto, SP 15054-000
ritaperuquetti@yahoo.com.br
Chromatoid body (CB) is a cytoplasmic structure of germ cells that has probable role in the RNA and protein reserve in the
different stages of spermiogenesis. Some authors believe that CB is formed by extrusion of nucleolar material from the nucleus
to the cytoplasm. This nucleolar cycle has been studied during spermatogenesis of some animal groups. The aim of the present
study is to follow the nucleolar cycle in fish. The used specie was the Tilapia rendalli, specie brought from Congo (Africa) to
Brazil, in 1953 and that, currently, it meets spread in all the dams of Brazil widely. The CB formation is an important aspect of
the animal reproduction. We need to improve our knowledge on this process and to know how it happens in T. rendalli, specie
that has a great economic importance and is widely cultivated in captivity in Brazil. The testes of each animal were removed,
sliced into small pieces and samples of the seminiferous tubules were minced and fixed by immersion with 3% glutaraldehyde
plus 0.25% tannic acid solution in Millonig’s buffer (pH 7.3) containing 0.54% glucose for 24 hours. After washing with the
same buffer, samples were post-fixed with 1% osmium tetroxide for 1hour, washed in Millonig’s buffer, dehydrated in a graded
acetone series, and embedded in Araldite resin. Ultrathin silver sections were cut using a diamond knife and stained with 2%
alcoholic uranyl acetate for 30 minutes followed by 2% lead citrate in sodium hydroxide for 10 minutes. Samples were evaluated
using a Leo-Zeiss 906 (Cambridge, UK) transmission electron microscope (TEM). Cytoplasmic “nuages” was originated
in spermatogonia when the nucleoli is organized yet (Figure 1A). CB had it’s major volume in the cytoplasm of primary spermatocytes,
after the nucleolus disorganization. CB was observed in association with mitochondrial aggregates in this type of
cell (Figure 1B). Later spermatids presented CB in migration to axonema region (Figure 1C) and the nucleolus was reorganized
with a small volume than the spermatogonia nucleolus. In the mature spermatozoon no CB material was found (Figure 1D). In
conclusion, data demonstrated that there is disintegration of the nucleolus and a fraction of this nucleolar material, probably,
migrates to the cytoplasm, where a specific structure is formed, called chromatoid body. This cytoplasmic structure participates
in some parts of spermiogenesis process: tail and middle piece formation of the spermatozoon, cellular communication between
spermatids.
Figure 1: A – Spermatogonia. B – Primary
Spermatocyte. C – Later Spermatid. D –
Spermatozoon. (n: nucleus; nu: nucleolus; *
and cb: chromatoid body material; mi:
mitochondria; f: flagellum. Bars = 10 µm.