Stages of oocyte development in the zebrafish, Brachydanio rerio
TL;DR: This staging series lays the foundation for future studies on the cellular processes occurring during oocyte development in zebrafish and should be useful for experimentation that requires an understanding of stage‐specific events.
Abstract: Oocyte development has been divided into five stages in the zebrafish Brachydanio rerio, based on morphological criteria and on physiological and biochemical events. In stage I (primary growth stage), oocytes reside in nests with other oocytes (Stage IA) and then within a definitive follicle (Stage IB), where they greatly increase in size. In stage II (cortical alveolus stage), oocytes are distinguished by the appearance of variably sized cortical alveoli and the vitelline envelope becomes prominent. In stage III (vitellogenesis), yolk proteins appear in oocytes and yolk bodies with crystalline yolk accrue during this major growth stage. Ooctes develop the capacity to respond in vitro to the steroid 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) by undergoing oocyte maturation. In stage IV (oocyte maturation), oocytes increase slightly in size, become translucent, and their yolk becomes non-crystalline as they undergo final meiotic maturation in vivo (and in response to DHP in vitro). In stage V (mature egg), eggs (approx. 0.75 mm) are ovulated into the ovarian lumen and are capable of fertilization. This staging series lays the foundation for future studies on the cellular processes occurring during oocyte development in zebrafish and should be useful for experimentation that requires an understanding of stage-specific events. © 1993 Wiley-Liss, Inc.
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TL;DR: It is demonstrated that zebrafish Piwi (Ziwi) is expressed in both the male and the female gonad and is a component of a germline-specifying structure called nuage, implicating a role for piRNAs in the silencing of repetitive elements in vertebrates.
1,034 citations
Cites background from "Stages of oocyte development in the..."
...Stages of oogenesis are oogonia (OG), stage I oocytes (7–140 mm; I), stage II oocytes (140–340 mm; II), stage III oocytes (340–690 mm; not in picture; III), and stage IV oocytes (0.69–0.73 mm; Selman et al., 1993)....
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TL;DR: Recent advances on teleost fish oocyte differentiation, maturation and ovulation are highlighted, including those involved in the degeneration and reabsorption of ovarian follicles (atresia).
910 citations
TL;DR: The genetic mechanisms underpinning oocyte and embryo growth and development are a priority for research and the products synthesized in ovoand the mechanisms controlling their expression are likely to play a central role in determining egg quality.
Abstract: Factors affecting egg quality are determined by the intrinsic properties of the egg itself and the environment in which the egg is fertilized and subsequently incubated. Egg quality in fish is very variable. Some of the factors affecting egg quality in fish are known, but many (probably most) are unknown. Components that do affect egg quality include the endocrine status of the female during the growth of the oocyte in the ovary, the diet of the broodfish, the complement of nutrients deposited into the oocyte, and the physiochemical conditions of the water in which the eggs are subsequently incubated. In captive broodfish, the husbandry practices to which fish are subjected are probably a major contributory factor affecting egg quality. Our knowledge of the genetic influences on egg quality is very limited indeed. We know that parental genes strongly influence both fecundity and egg quality, but almost nothing is known about gene expression and/or mRNA translation in fish oocytes/embryos. This is surprising because the products synthesized in ovoand the mechanisms controlling their expression are likely to play a central role in determining egg quality. The genetic mechanisms underpinning oocyte and embryo growth and development are a priority for research
807 citations
Cites background from "Stages of oocyte development in the..."
...…classi®ed into six phases, according to the state of oocyte growth; they are: oogenesis, primary oocyte growth, cortical alveolus stage, vitellogenesis, maturation and ovulation (Nagahama, 1983; Selman et al., 1986, 1993; Bromage and Cumaranatunga, 1988; Tyler, 1991; Tyler and Sumpter, 1996)....
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...The genetic changes and ultrastructural events accompanying oocyte development in teleosts are described in Nakamura and Nagahama (1993) and Selman et al. (1993)....
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...There are reports, however, in the zebra ®sh (Brachydanio rerio, Cyprinidae; Selman et al., 1993) and in the blue tiliapia (Tilapia aurea, Oreochromis aureus, Cichlidae; Ding et al....
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...Yolk proteins are stored either in a crystalline platelet form (zebra ®sh, Selman et al., 1993), or, as is more common, in ¯uid-®lled yolk spheres or globules (Wallace and Selman, 1981)....
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...There are reports, however, in the zebra ®sh (Brachydanio rerio, Cyprinidae; Selman et al., 1993) and in the blue tiliapia (Tilapia aurea, Oreochromis aureus, Cichlidae; Ding et al., 1989) that more than one type of VTG molecule may exist....
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TL;DR: The mechanisms that control oocyte growth are addressed in this review, albeit that the available information, as in all other vertebrates, is very limited.
Abstract: Oocyte growth and development is an important issue in fish and fisheries biology. This paper reviews the information available on oocyte growth patterns and the rates and dynamics of oocyte growth in teleosts. In synchronous spawners, the weight of the gonad may represent as much as 40% of the overall body weight of the fish. In asynchronous spawners, the weight of the mature ovary is considerably less than in synchronous ovulators, but the ovary shows a more regular periodicity and may grow repeatedly many times during the breeding season. There is a huge variability in egg size in teleosts, with the largest known measuring up to 8 cm in diameter. Within the limits of variance set by genetic constraints, egg size may vary between populations of the same species. Oocytes in all teleosts undergo the same basic pattern of growth: oogenesis, primary oocyte growth, cortical alveolus stage, vitellogenesis, maturation and ovulation. The mechanisms that control oocyte growth are addressed in this review, albeit that the available information, as in all other vertebrates, is very limited. The main hormones that have been shown to affect ovarian growth are gonadotrophin, thyroid hormones, growth hormone, insulin and insulin-like growth factors. An overview of the determinants of fecundity, with particular reference to oocyte recruitment and atresia, is the focus of the second part of the paper. Genetics and nutrition have major effects on fecundity, and studies so far suggest that the determinants of fecundity usually operate during the early part of gametogenesis. The role of atresia in determining fecundity is less clear. The final part of this review highlights some areas of study that are priorities for research on ovarian development in fish.
782 citations
Cites background from "Stages of oocyte development in the..."
...This is also the case for some teleosts, for example in the zebra fish (Selman et al., 1993)....
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...Recent studies, however, in the zebra fish (Selman et al., 1993) and tilapia (Ding et al....
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TL;DR: This review is an attempt to integrate the available scientific information related to zebrafish biology and culture into an overview of the field that can be used to improve the efficiency with which this important model animal is used in research.
607 citations
References
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TL;DR: This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr with little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose.
225,085 citations
Book•
01 Jan 1995
6,168 citations
TL;DR: Teleosts offer examples of virtually every conceivable type of ovarian physiology and provide a wealth of experimental material for exploring the cellular and hormonal mechanisms which regulate oocyte recruitment and growth throughout ovarian recrudescence.
Abstract: SYNOPSIS. Four principal stages of oocyte growth are recognized among teleosts. During gonadotropin-independent primary growth, multiple nucleoli form as well as a Balbiani body which eventually disperses throughout the ooplasm. The first gonadotropin-dependent stage involves the formation of yolk vesicles, the precursors to the cortical alveoli. True vitellogenesis follows during which vitellogenin is sequestered from the maternal blood and packaged into yolk granules or spheres. The latter generally fuse centripetally at some time during oocyte growth to give a continuous fluid phase surrounded by a peripheral layer of cytoplasm containing the cortical alveoli. Maturation represents the final stage and is accompanied in many teleosts by water uptake; among marine teleosts with pelagic eggs, most of the final egg volume may be achieved by this process. Ovaries may be synchronous, asynchronous, or group-synchronous. Among the latter, a clutch of oocytes may be recruited from an asynchronous population of earlier stages into any of the subsequent stages. In teleosts which spawn repeatedly, recruitment of new clutches can usually be associated with the transition of a previously recruited clutch from one stage to the next. Teleosts thus offer examples of virtually every conceivable type of ovarian physiology and provide a wealth of experimental material for exploring the cellular and hormonal mechanisms which regulate oocyte recruitment and growth throughout ovarian recrudescence.
1,270 citations
TL;DR: This chapter discusses germ plasm and the differentiation of the germ cell line and the histochemical evidence for the presence of RNA in polar granules of insects and germinal plasm of amphibians indicates that RNA is present only in eggs and early embryos, while a protein component is present throughout the germ cycle.
Abstract: Publisher Summary This chapter discusses germ plasm and the differentiation of the germ cell line. Germ plasm is defined as a substance present in the cytoplasm of gametes, which is segregated into specific cells during blastulation and determines that those cells shall become the progenitors of the germ cell line during subsequent development. The composition of germ plasm is discussed. The histochemical evidence for the presence of RNA in polar granules of insects and germinal plasm of amphibians indicates that RNA is present only in eggs and early embryos, while a protein component is present throughout the germ cell cycle. Good morphological and experimental evidence for the presence of germ plasm is available for only a few animal species. The germinal cells of chaetognaths were present in early stages of embryonic development and identified a group of cells at the bottom of the archenteron cavity in gastrulas of Sagitta as the primordium of the germ line. Experimental studies are given to determine the role of germinal plasm in anuran eggs by altering the cytoplasm in which it is contained.
599 citations
TL;DR: Epiboly, involution and convergent extension in zebrafish involve the same kinds of cellular rearrangements as in amphibians, and they occur during comparable stages of embryogenesis.
Abstract: Beginning during the late blastula stage in zebrafish, cells located beneath a surface epithelial layer of the blastoderm undergo rearrangements that accompany major changes in shape of the embryo. We describe three distinctive kinds of cell rearrangements. (1) Radial cell intercalations during epiboly mix cells located deeply in the blastoderm among more superficial ones. These rearrangements thoroughly stir the positions of deep cells, as the blastoderm thins and spreads across the yolk cell. (2) Involution at or near the blastoderm margin occurs during gastrulation. This movement folds the blastoderm into two cellular layers, the epiblast and hypoblast, within a ring (the germ ring) around its entire circumference. Involuting cells move anteriorwards in the hypoblast relative to cells that remain in the epiblast; the movement shears the positions of cells that were neighbors before gastrulation. Involuting cells eventually form endoderm and mesoderm, in an anterior-posterior sequence according to the time of involution. The epiblast is equivalent to embryonic ectoderm. (3) Mediolateral cell intercalations in both the epiblast and hypoblast mediate convergence and extension movements towards the dorsal side of the gastrula. By this rearrangement, cells that were initially neighboring one another become dispersed along the anterior-posterior axis of the embryo. Epiboly, involution and convergent extension in zebrafish involve the same kinds of cellular rearrangements as in amphibians, and they occur during comparable stages of embryogenesis.
564 citations