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Aquaculture, especially of marine species, is quite a new agricultural activity in relation to domestic animal production. With the exception of carp culture (family Cyprinidae) in Asia which started many centuries ago, and rainbow trout (Oncorhynchus mykiss) farming in Europe and North America which was commercialized in the last century, aquaculture as we know it is being practiced for only a few decades (Kirk, 1987). As a result, it is doubtful that a "domestic" fish species exists today, at least according to the interpretation of the word in terrestrial animal husbandry. In addition, even carp and rainbow trout, which are considered highly domesticated, do not reproduce readily in captivity. [ABSTRACT FROM AUTHOR]

Ensuring the retention of a record of the genetic diversity of species involves, at its simplest form, the long-term storage of material from somatic and reproductive cell lines. However, to have real practical benefit such material should be in the form of viable cellular material, ideally from the germline or reproductive cell lines. The ability to generate banks of cryopreserved sperm, eggs, and embryos that retain full viability following recovery from the frozen state would be the most powerful facilitating tool in species conservation and commercial applications such as aquaculture. The nuclear genomes of fish show a full range of sex chromosome differentiation, ranging from the all-autosomal karyotype as seen in the zebrafish to the genetically and cytogenetically differentiated sex chromosomes seen in the guppy (Traut and Winking, 2001). The preservation of haploid genomes in the viable form of male and female reproductive cells, or of viable embryos, is vital if normal populations of males and females are to be established. [ABSTRACT FROM AUTHOR]

The basic morphological and biochemical aspects of fertilization are highly conserved and make use of principles common to most metazoan animals. However, fertilization of the fish oocyte occurs in a wide variety of environmental circumstances and the details for bringing sperm and egg together, as well as for transforming the fertilized oocyte into a developing embryo can differ greatly. Adaptations for activating a yolk-rich oocyte typically found in fish species and establishing polarity of the embryo involve some processes that appear to be unique to fish oocytes. Such unique aspects of fish fertilization provide opportunities to understand mechanisms that are more difficult to detect in oocytes from other types of animals. The following sections will review the current knowledge relating to strategies of fertilization, mechanisms of gamete interaction, and egg activation in fish species. [ABSTRACT FROM AUTHOR]

As in other lower vertebrates, teleost oocytes growing within the ovary pass through a series of developmental stages that eventually culminate in the production of a mature female gamete or egg. During most of its time they are temporarily arrested in meiotic prophase I, and energy expenditures are concentrated on the synthesis and uptake of various substances (e.g. vitellogenin (Vg) ) required by the developing oocyte and subsequent embryo development. After oocyte growth, meosis resumes as the large nucleus or germinal vesicle breaks down (GVBD), half the chromosomes are eliminated into a small polar body by unequal cytokinesis, and the remainder becomes aligned in second meiotic metaphase at the animal pole. During this process, termed "meiotic maturation", or "oocyte maturation", ovulation generally occurs. Shortly after second meiotic metaphase is achieved, the oocyte becomes "activable" or capable of being fertilized, and hence becomes an egg. [ABSTRACT FROM AUTHOR]

Oocytes are produced in the ovaries by the entry of mitotically proliferating oogonia into meiosis. In vertebrates, including fishes, oocytes stop their meiotic cell cycle at prophase I, during which they grow by the accumulation of substances, such as yolk and mRNAs, necessary for early embryonic development (see Chapters 1-3). These prophase I-arrested oocytes are still immature and unable to be fertilized even when they reach their fully grown stage. Hormonal stimulation allows the oocytes to resume meiosis and proceed to metaphase II, where meiosis stops again. These metaphase II-arrested oocytes are now mature (called ova or eggs) and can undergo embryonic development when fertilized. The process from prophase I arrest to metaphase II arrest is termed oocyte maturation in the field of biological sciences or final oocyte maturation in the field of fisheries sciences (Figure 1). [ABSTRACT FROM AUTHOR]

Public concern about the potential effects of endocrine disrupting chemicals (EDCs) on wildlife and human health has heightened experimental paradigms to assess the mechanistic effects of exposure to these compounds. The worry stems from the known effects caused in humans by exposure of pregnant mothers to the synthetic estrogen, diethylstilbestrol (DES) to help them avoid miscarriage (Milhan, 1992). The effects were observed 20 years after the initial exposure of the mothers and resulted in a higher than normal chance of inducing rare endocrine-related cancers as well as other reproductive abnormalities in their progeny. [ABSTRACT FROM AUTHOR]

In fish, cyclic ovarian development is synchronized by hormones that are predominantly produced by the brain, pituitary, and ovary. These hormones act to promote early development of ovarian follicles, vitellogenesis, oocyte growth, differentiation, maturation into a preovulatory oocyte, and finally the release of a group of eggs through the process of ovulation. The brain and pituitary comprise the neuroendocrine level of control and are constantly regulated through feedback mechanism by ovarian hormones (see Chapters 7 and 8). [ABSTRACT FROM AUTHOR]

The ovarian follicle is not only the major site of synthesis of estrogens, androgens, and progestins in female vertebrates, but is also an important target for sex steroid hormones. Both classic (genomic) and rapid, nongenomic actions of estrogens, androgens, and progestins have been described in the ovaries of a variety of vertebrate species, as well as the nuclear and membrane receptors thought to mediate these effects. The teleost ovary has proven to be a particularly useful model for investigating nongenomic steroid actions and the receptors on the plasma membrane through which they act. However, a comprehensive understanding of the precise physiological functions of many steroid receptors in teleost ovaries is currently lacking. In this chapter recent developments in steroid receptor research in the teleost ovary are briefly reviewed and some major gaps in our knowledge of their roles in ovarian function identified. [ABSTRACT FROM AUTHOR]

Vertebrate reproduction is regulated by the gonadotropic hormones, folliclestimulating hormone (FSH) and luteinizing hormone (LH), both synthesized and secreted by the pituitary gland. Their coordinated action enables fine-tuning of ovarian and testicular function. FSH in certain fish (e.g. salmonids) has a dominant role in the initiation of gametogenesis and regulation of gonadal growth, whereas LH is dominant mainly during gonadal maturation and spermiation/ ovulation. [ABSTRACT FROM AUTHOR]

Maternal factors are essential for early animal development, including fish species. The teleost fish Danio rerio, commonly known as zebrafish, has become a valuable model system to study fish (and vertebrate) biological processes due to its potential to combine genetic, embryological and molecular methods. This chapter attempts to summarize current knowledge on the role of maternal factors in this organism, although studies on the subject carried out in other fish species, when available, are also included. [ABSTRACT FROM AUTHOR]

All vertebrate species produce an egg surrounded by an acellular vitelline envelope. In mammals the envelope is transparent and called the zona pellucida. The zona pellucida consists of 2-4 major proteins (Wassarman, 1988; Lefièvre et al., 2004). [ABSTRACT FROM AUTHOR]

This chapter describes the implementation of the new proteomics technologies to the study of the protein repertoires of developing oocytes. Proteomics is a new analytical field aimed at simultaneously characterizing entire protein repertoires of biological systems. Using proteomics, comprehensive lists of the protein constituents of cells and organisms can be established. Even more importantly for developmental biology, changes in the relative amounts of the proteins and in the patterns of their posttranslational modifications can be followed. Here we will review the way proteomics technologies based on one or two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), multidimensional high-performance liquid chromatography (HPLC) and mass spectrometry were employed for following molecular changes in oocyte development. Indeed, proteomes of different developmental stages of oocytes of different species have been studied, revealing both the similarities and the differences. This chapter will allude to the effects of hormonal cues and cryopreservation on the protein repertoires of oocytes and their influence on viability and fertilization failures. [ABSTRACT FROM AUTHOR]

The ability of an oocyte to develop into a viable embryo depends on the accumulation of specific maternal information and molecules, such as RNAs and proteins. Folliculogenesis and oogenesis include the formation of ovarian follicles, the initiation and completion of meiosis, and the accumulation of specific information and molecules such as RNAs, proteins, or imprinted genes in the female germ cells to sustain embryo development to the stage where zygotic gene activation takes over (Matova and Cooley, 2001; Eichenlaub-Ritter and Peschke, 2002; Duranthon and Renard, 2003). As in other vertebrates (Matova and Cooley, 2001), somatic gonadal cells in ray-finned fish species surround a single oocyte to establish a follicle (Selman and Wallace, 1989; Selman et al., 1993; Chapter 1). [ABSTRACT FROM AUTHOR]

The ability of an oocyte to develop into a viable embryo depends on the accumulation of specific maternal information and molecules. Oocyte growth, particularly in oviparous species, is characterized by the intense deposition of products; e.g. RNAs, proteins (including growth and transcription factors), lipids, vitamins, and hormones. The deposit and storage occur in teleost fish species in a physiologically arrested cell at the G2/M border in first meiotic prophase (see Chapter 1).Whereas the nucleus remains in the diplotene stage, maternal RNAs are produced endogenously by the oocyte (see Chapters 3 and 6). [ABSTRACT FROM AUTHOR]

The animal kingdom exhibits two particular diploid cell types: cells forming the organism or somatic cells, which remain diploid; and germinal line cells that generate haploid reproductive cells, or gametes. Diploid cells in the germinal line, known as primordial germ cells (PGC), are singled out very early in embryogenesis and migrate towards the genital crests from which ovaries or testes derive. As soon as the PGC colonize the ovary, they become associated with somatic cells in the stroma, which differentiate at the same time as the germinal cells. Indeed, in Actinopterygii (ray-finned fish), as in other vertebrates, the development of oocytes in the ovaries is inevitably linked with that of the surrounding somatic layers. An oocyte and its layers of specialized somatic cells constitute an ovarian follicle (for detailed reviews of the cellular events in oocyte growth and development in Teleostei see: Wallace and Selman, 1981; Guraya, 1986; Selman and Wallace, 1989; Selman et al., 1993). [ABSTRACT FROM AUTHOR]