ABSTRACT
Fish oogenesis has already been thoroughly studied. The numerous contributions to this field have been reviewed by many authors. These reviews have specifically focused on the different steps of oogenesis including vitellogenesis, oocyte maturation and ovulation as well as their endocrine control (Wallace and Selman, 1981; Fostier and Jalabert, 1982; Goetz, 1983; Guraya, 1986; Goetz et al., 1991; Jalabert et al., 1991; Nagahama, 1994; Nagahama et al., 1994, 1995; Yaron, 1995; Goetz and Garczynski, 1997; Patino et al., 2001, 2003; Patino and Sullivan, 2002). In addition, the large number of fish species (over 28,000 identified so far), exhibiting a great variety of reproductive strategies, has incited many species-specific studies. On the other hand, the issue of fish egg quality has also generated vast interest from many investigators
(see Kjörsvik et al., 1990; Brooks et al., 1997 for review). Many studies on the determinism of fish egg quality have focused on the composition of yolk reserves accumulated during vitellogenesis, including the potential role of trophic elements such as fatty acids, free amino acids, vitamins, metabolic enzymes, etc. In contrast, the non-yolky content of egg cytoplasm, including RNAs, structure and regulatory proteins, and cortical alveoli content, has received far less attention. Yet, many of these constituents can be expected to play a role in yolk processing, fertilization, and control of early embryo development. On the other side, postvitellogenic ovarian events, i.e., oocyte maturation and ovulation-that occur in a relatively short time at the end of yolk deposition and concern all egg compartments-are also known to be of great importance to ensure ovulation of a developmentally competent oocyte. However, most available analytical studies focus on the nature of endocrine, paracrine and autocrine signalling of meiosis resumption (oocyte maturation) and ovulation, but without paying too much attention to qualitative aspects of the results, i.e., the production of good quality eggs.
