Histochemical characterisation of oocytes of the swordfish &lt;i&gt;Xiphias gladius&lt;/i&gt;

Juan B Ortiz-Delgado,Carmen Sarasquete,Serena Porcelloni,Cristina Fossi

doi:10.3989/scimar.2008.72n3549

Abstract

This paper reports a histological, histochemical and immunohistochemical characterisation of growing oocytes of the swordfish Xiphias gladius. The presence and distribution of carbohydrates, proteins, lipids, calcium, iron, vitellogenin/Vg, zona radiata protein/Zrp, metallothionein/Mt, and thyroid hormones/T3-T4 were studied during oogenesis (cortical alveoli, globules, yolk-granules, cytoplasm, follicular and radiata envelopes). During the initial vitellogenic phase, the oocytes showed cortical alveoli and oil globules containing neutral lipids exclusively. During this phase, small yolk granules appeared around the peripheral cytoplasm, and they increased through exogenous vitellogenesis. Yolk granules were composed of glycoproteins, calcium, iron, and proteins rich in lysine, arginine, tyrosine, tryptophan, cysteine and cystine. Vg and Mt were immunohistochemically detected in yolk. The follicular envelope contained proteins rich in amino acids. Moreover, calcium and thyroid hormones (triiodotyronine and thyroxine/T3, T4) were detected in this cell envelope. Cortical alveoli, which contained carboxylated and neutral glycoconjugates, were especially rich in N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, galactose and sialic acid. Finally, the zona radiata was mainly proteinaceous in nature and was composed of calcium and neutral glycoproteins. The egg envelope or chorion and the liver showed specific immunoreactivities by using anti-salmon Zrp as the primary antiserum.

Highlights

During the reproductive cycle of fish species, the chemical composition of the fish oocytes and the mobilisation of macromolecules and cations between the liver and gonads have been studied by several authors (Wallace, 1978; Khoo, 1979; Gutiérrez et al, 1985, Selman and Wallace, 1986; Mayer et al, 1988; González de Canales et al, 1992, Sarasquete et al, 1993; Muñoz-Cueto et al, 1996; Grau et al, 1996; Corriero et al, 2004)
SUMMARY: This paper reports a histological, histochemical and immunohistochemical characterisation of growing oocytes of the swordfish Xiphias gladius
The presence and distribution of carbohydrates, proteins, lipids, calcium, iron, vitellogenin/ Vg, zona radiata protein/zona radiata proteins (Zrp), metallothionein/Mt, and thyroid hormones/T3-T4 were studied during oogenesis

Summary

Introduction

During the reproductive cycle of fish species, the chemical composition of the fish oocytes (cytoplam, cortical alveoli, yolk, zona radiata, granulosa and theca layers) and the mobilisation of macromolecules and cations between the liver and gonads have been studied by several authors (Wallace, 1978; Khoo, 1979; Gutiérrez et al, 1985, Selman and Wallace, 1986; Mayer et al, 1988; González de Canales et al, 1992, Sarasquete et al, 1993; Muñoz-Cueto et al, 1996; Grau et al, 1996; Corriero et al, 2004). The histochemical localisation of specific metal-bindingproteins (metallothionein/Mt), cations (calcium, iron), thyroid hormones and specific lectin-glycoconjugates during fish oogenesis has received less attention (Sarasquete et al, 2002 a,b; Motta et al, 2005). Glycoconjugates may be involved in binding of hormones; in bacteria agglutination; in the transport of metabolites and ions across the plasmalema; in sperm-egg binding; and in polyspermic inhibition (Prokop et al, 1974; Miller and Ax, 1990; Skutelsky et al, 1994; Motta et al, 2005)

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