Ultrastructure of the ovarian follicles in the placentotrophic Andean lizard of the genus Mabuya (Squamata: Scincidae)

We studied the ultrastructural organization of the ovarian follicles in a placentotrophic Andean lizard of the genus Mabuya. The oocyte of the primary follicle is surrounded by a single layer of follicle cells. During the previtellogenic stages, these cells become stratified and differentiated in three cell types: small, intermediate, and large globoid, non pyriform cells. Fluid‐filled spaces arise among follicular cells in late previtellogenic follicles and provide evidence of cell lysis. In vitellogenic follicles, the follicular cells constitute a monolayered granulosa with large lacunar spaces; the content of their cytoplasm is released to the perivitelline space where the zona pellucida is formed. The oolemma of younger oocytes presents incipient short projections; as the oocyte grows, these projections become organized in a microvillar surface. During vitellogenesis, cannaliculi develop from the base of the microvilli and internalize materials by endocytosis. In the juxtanuclear ooplasm of early previtellogenic follicles, the Balbiani's vitelline body is found as an aggregate of organelles and lipid droplets; this complex of organelles disperses in the ooplasm during oocyte growth. In late previtellogenesis, membranous organelles are especially abundant in the peripheral ooplasm, whereas abundant vesicles and granular material occur in the medullar ooplasm. The ooplasm of vitellogenic follicles shows a peripheral band constituted by abundant membranous organelles and numerous vesicular bodies, some of them with a small lipoprotein core. No organized yolk platelets, like in lecithotrophic reptiles, were observed. Toward the medullary ooplasm, electron‐lucent vesicles become larger in size containing remains of cytoplasmic material in dissolution. The results of this study demonstrate structural similarities between the follicles of this species and other Squamata; however, the ooplasm of the mature oocyte of Mabuya is morphologically similar to the ooplasm of mature oocytes of marsupials, suggesting an interesting evolutionary convergence related to the evolution of placentotrophy and of microlecithal eggs. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Oogenesis in the leech Glossiphonia heteroclita (Annelida, Hirudinea, Glossiphoniidae) II. Vitellogenesis, follicle cell structure and egg shell formation

By the end of previtellogenesis, the oocytes of Glossiphonia heteroclita gradually protrude into the ovary cavity. As a result they lose contact with the ovary cord (which begins to degenerate) and float freely within the hemocoelomic fluid. The oocyte's ooplasm is rich in numerous well-developed Golgi complexes showing high secretory activity, normal and transforming mitochondria, cisternae of rER and vast amounts of ribosomes. The transforming mitochondria become small lipid droplets as vitellogenesis progresses. The oolemma forms microvilli, numerous coated pits and vesicles occur at the base of the microvilli, and the first yolk spheres appear in the peripheral ooplasm. A mixed mechanism of vitellogenesis is suggested. The eggs are covered by a thin vitelline envelope with microvilli projecting through it. The envelope is formed by the oocyte. The vitelline envelope is produced by exocytosis of vesicles containing two kinds of material, one of which is electron-dense and seems not to participate in envelope formation. The cortical ooplasm of fully grown oocytes contains many cytoskeletal elements (F-actin) and numerous membrane-bound vesicles filled with stratified content. Those vesicles probably are cortical granules. The follicle cells surrounding growing oocytes have the following features: (1) they do not lie on a basal lamina; (2) their plasma membrane folds deeply, forming invaginations which eventually seem to form channels throughout their cytoplasm; (3) the plasma membrane facing the ovary lumen is lined with a layer of dense material; and (4) the plasma membrane facing the oocyte forms thin projections which intermingle with the oocyte microvilli. In late oogenesis, the follicle cells detach from the oocytes and degenerate in the ovary lumen.     

Heterologous gap junctions between oocytes and follicle cells of an insect,Dysdercus intermedius,and their potential role as ion current pathways

Summary In telotrophic insect ovaries, the oocytes develop in association with two kinds of supporting cells. Each ovary contains five to seven ovarioles. An ovariole consists of a single strand of several oocytes. At the apex of each ovariole is a syncytium of nurse cells (the tropharium), which connects by strands of cytoplasm (the trophic cords) to four or more previtellogenic oocytes. In addition, each oocyte is surrounded by an epithelium of follicle cells, with which it may form gap junctions. To study the temporal and spatial patterns of these associations, Lucifer yellow was microinjected into ovaries of the red cotton bug, Dysdercus intermedius. Freeze-fracture replicas were examined to analyze the distribution of gap junctions between the oocyte and the follicle cells. Dye-coupling between oocytes and follicle cells was detectable early in previtellogenesis and was maintained through late vitellogenesis. It was restricted to the lateral follicle cells. The anterior and posterior follicle cells were not dye-coupled. Freeze-fracture analysis showed microvilli formed by the oocyte during mid-previtellogenesis, and the gap junctions became located at the tips of these. As the microvilli continued to elongate until late vitellogenesis, gap junction particles between them and follicle cell membranes became arranged in long arrays. The morphological findings raise questions about pathways for the intrafollicular phase of the ion currents known to surround the previtellogenic and vitellogenic growth zones of the ovariole.Supported by the Deutsche Forschungsgemeinschaft (Schwerpunkt Differenzierung)     

Previtellogenic oocytes of South African largemouth bass Micropterus salmoides Lacépède 1802 (Actinopterygii,Perciformes) - the Balbiani body,cortical alveoli and developing eggshell

The ovaries of the largemouth bass Micropterus salmoides, an alien and invasive species in South Africa, contain a germinal epithelium which consists of germline and somatic cells, as well as previtellogenic and late vitellogenic ovarian follicles. The ovarian follicle consists of an oocyte surrounded by follicular cells and a basal lamina; thecal cells adjacent to this lamina are covered by an extracellular matrix. In this article, we describe the Balbiani body and the polarization and ultrastructure of the cytoplasm (ooplasm) in previtellogenic oocytes. The nucleoplasm in all examined oocytes contains lampbrush chromosomes, nuclear bodies and several nucleoli near the nuclear envelope. The ultrastructure of the nucleoli is described. Numerous nuage aggregations are present in the perinuclear cytoplasm in germline cells as well as in the ooplasm. Possible roles of these aggregations are discussed. The ooplasm contains the Balbiani body, which defines the future vegetal region in early previtellogenic oocytes. It is comprised of nuage aggregations, rough endoplasmic reticulum, Golgi apparatus, mitochondria, complexes of mitochondria with nuage-like material, and lysosome-like organelles. In mid-previtellogenic oocytes, the Balbiani body surrounds the nucleus and later disperses in the ooplasm. The lysosome-like organelles fuse and transform into vesicles containing material which is highly electron dense. As a result of the fusion of the vesicles of Golgi and rough endoplasmic reticulum, the cortical alveoli arise and distribute uniformly throughout the ooplasm of late previtellogenic oocytes. During this stage, the deposition of the eggshell (zona radiata) begins. The eggshell is penetrated by canals containing microvilli and consists of the following: the internal and the external egg envelope. In the external envelope three sublayers can be distinguished.     

Ultra- and microstructure of the female reproductive system of Matsucoccus matsumurae

The ultra- and microstructure of the female reproductive system of Matsucoccus matsumurae was studied using light microscopy, scanning and transmission electron microscopy. The results revealed that the female reproductive system of M. matsumurae is composed of a pair of ovaries, a common oviduct, a pair of lateral oviducts, a spermatheca and two pairs of accessory glands. Each ovary is composed of approximately 50 telotrophic ovarioles that are devoid of terminal filaments. Each ovariole is subdivided into an apical tropharium, a vitellarium and a short pedicel connected to a lateral oviduct. The tropharium contains 8–10 trophocytes and two early previtellogenic oocytes termed arrested oocytes. The trophocytes degenerate after egg maturation, and the arrested oocytes are capable of further development. The vitellarium contains 3–6 oocytes of different developmental stages: previtellogenesis, vitellogenesis and choriogenesis. The surface of the vitellarium is rough and composed of a pattern of polygonal reticular formations with a center protuberance. The oocyte possesses numerous yolk spheres and lipid droplets, and is surrounded by a mono-layered follicular epithelium that becomes binucleate at the beginning of vitellogenesis. Accessory nuclei are observed in the peripheral ooplasm during vitellogenesis.     

Structure of ovaries and oogenesis in Corydalidae and Chauliodidae (Insecta, Megaloptera). I. Architecture of adult ovarioles and previtellogenesis.

The results of histological and EM studies on the ovaries of three representatives of Megaloptera: Chauliodes pectinicornis, Nigronia fasciata (Chauliodidae), and Corydalus peruvianus Corydalidae) are presented. It is shown that the ovaries of all 3 investigated species are panoistic (secondary panoistic, = neopanoistic) and consist of numerous (more than a hundred) ovarioles that are differentiated into 3 well-defined regions: the terminal filament, the germarium, and the vitellarium. The germaria of adult females are apparently non-functional and contain germ and somatic cells in various stages of degeneration. The vitellaria are composed of 12-15 developing ovarian follicles (= oocytes surrounded by follicular cells) in a linear arrangement. In adult females these follicles can be classified into early previtellogenic, late previtellogenic, vitellogenic, and choriogenic. During early previtellogenesis oocyte nuclei (= germinal vesicles) contain single nucleolar masses. Histochemical analyses indicate that within the masses DNA as well as AgNOR proteins are present. During subsequent stages of the previtellogenic growth nucleolar masses gradually break down into smaller aggregations of coarse granular material, i.e. multiple nucleoli. In chauliodids the nucleoli are distributed evenly throughout the nucleoplasm while in the corydalid, C. peruvianus, they form a characteristic ring. The presented results are discussed in a phylogenetic context.     

Microsporidia infect the Liophloeus lentus (Insecta, Colepotera) ovarioles, developing oocytes and eggs

In the ovarioles of Liophloeus lentus (Insecta, Coleoptera, Curculionidae) two types of bacteria and parasitic microorganisms belonging to Microsporidia have been found. This study shows that the different microsporidian life stages (meronts, sporonts, sporoblasts and spores) infect the outer ovariole sheath, trophic chambers, follicular cells, late previtellogenic and vitellogenic oocytes and eggs. In trophic chambers the parasites are very abundant and are distributed unevenly, i.e. their large mass occupies the syncytial cytoplasm between the nurse cell nuclei, whereas the neck region of the trophic chamber (which houses young oocytes, prefollicular cells and trophic cords) is almost free of parasites. The developing oocytes and eggs contain a lower number of parasites which are usually distributed in the cortical ooplasm. The gross morphology of the ovaries is similar in infected and non-infected specimens. Similarly, the presence of a parasite seems to not disturb the course of oogensis. The only difference was found in the ultrastructure of mitochondria in young previtellogenic oocytes. In the infected females they are unusual i.e. bigger and spherical with tubullar cristae, whereas in the non-infected insects they are elongated and have lamellar cristae. As oogenesis progresses the unusual mitochondria rapidly change their morphology and become similar to the mitochondria in non-infected females. Taking into account the distribution of parasites within the ovarioles, it is suggested that they infect growing oocytes via outer ovariole sheath and follicular epithelium rather than via trophic cords.     

Germ cell cluster formation and ovariole structure in viviparous and oviparous generations of the aphid Stomaphis quercus

The developing ovaries of S. quercus contain a limited number of oogonial cells which undergo a series of incomplete mitotic divisions resulting in the formation of clusters of cystocytes. Ovaries of viviparous generations contain 6 to 9 clusters, containing 32 cystocytes each, whereas ovaries of oviparous generations contain 5 clusters containing 45-60 cystocytes. During further development, clusters become surrounded by a single layer of follicular cells, and within each cluster the cystocytes differentiate into oocytes and trophocytes (nurse cells). Concurrently, cysts transform into ovarioles. The anterior part of the ovariole containing the trophocytes becomes the tropharium, whereas its posterior part containing oocytes transforms into the vitellarium. The vitellaria of viviparous females are composed of one or two oocytes, which develop until previtellogenesis. The nuclei of previtellogenic oocytes enter cycles of mitotic divisions which lead to the formation of the embryo. Ovarioles of oviparous females contain a single oocyte which develops through three stages: previtellogenesis, vitellogenesis and choriogenesis. The ovaries are accompanied by large cells termed bacteriocytes which harbor endosymbiotic microorganisms.     

The ovaries of aphids (Hemiptera,Sternorrhyncha, Aphidoidea): morphology and phylogenetic implications

The ovaries of aphids belonging to the families Eriosomatidae, Anoeciidae, Drepanosiphidae, Thelaxidae, Aphididae, and Lachnidae were examined at the ultrastructural level. The ovaries of these aphids are composed of several telotrophic ovarioles. The individual ovariole is differentiated into a terminal filament, tropharium, vitellarium, and pedicel (ovariolar stalk). Terminal filaments of all ovarioles join together into the suspensory ligament, which attaches the ovary to the lobe of the fat body. The tropharium houses individual trophocytes and early previtellogenic oocytes termed arrested oocytes. Trophocytes are connected with the central part of the tropharium, the trophic core, by means of broad cytoplasmic processes. One or more oocytes develop in the vitellarium. Oocytes are surrounded by a single layer of follicular cells, which do not diversify into distinct subpopulations. The general organization of the ovaries in oviparous females is similar to that of the ovaries in viviparous females, but there are significant differences in their functioning: (1) in viviparous females, all ovarioles develop, whereas in oviparous females, some of them degenerate; (2) the number of germ cells per ovariole is usually greater in females of the oviparous generation than in females of viviparous generations; (3) in oviparous females, oocytes in the vitellarium develop through three stages (previtellogenesis, vitellogenesis, and choriogenesis), whereas in viviparous females, the development of oocytes stops after previtellogenesis; and (4) in the oocyte cytoplasm of oviparous females, lipid droplets and yolk granules accumulate, whereas in viviparous females, oocytes accrue only lipid droplets. Our results indicate that a large number of germ cells per ovariole represent the ancestral state within aphids. This trait may be helpful in inferring the phylogeny of Aphidoidea.     

Dynamics of the oocyte cortical cytoskeleton during oogenesis in Rhodnius prolixus

The oocyte cortex undergoes dramatic changes during oogenesis in Rhodnius prolixus. Despite numerous studies examining oogenesis in the telotrophic ovariole, none has investigated the ultrastructural details of the oocyte cortex, in particular, the lateral cortical cytoskeleton. Indirect immunofluorescent staining of sections, rhodamine phalloidin staining of whole mounts and scanning and transmission EM of permeabilized and unpermeabilized preparations revealed the dynamic changes of the oocyte cortex from early previtellogenesis through to late vitellogenesis. During early previtellogenesis, oocytes 50-150 mum in length have a smooth oolemma, with no discernible cortical cytoskeleton. During mid to late previtellogenesis (oocytes 150-350 mum in length) a tightly woven network of microfilaments and microtubules forms, excluding mitochondria and Golgi complexes from the lateral cortex. At the onset of vitellogenesis, the follicuiar epithelium becomes patent, and there is an increase in microvilli covering the lateral oocyte surface. The microfilament cores form a discrete pattern that corresponds to the imprint of the follicle cells on the oocyte surface. While the lateral microfilament cytoskeleton becomes more elaborate, the lateral microtubule cytoskeleton diminishes, remaining sparse throughout vitellogenesis. The oocyte cortical cytoskeleton undergoes dramatic changes during oogenesis. These cortical dynamics are intricately related to the cellular and molecular processes that occur during oogenesis.     

The Balbiani body in the oocytes of a common cellar spider, Pholcus phalangioides (Araneae: Pholcidae)

Previtellogenic oocytes of a common cellar spider, Pholcus phalangioides, contain a single aggregation of organelles referred here to as the Balbiani body. It is a well defined ooplasmic structure predominantly composed of fine granular nuage, RNA rich material but comprising also mitochondria, vesicles of endoplasmic reticulum and stacks of Golgi cysternae. The Balbiani body originates early during previtellogenesis in the form of a cap-shaped mass in juxtaposition to one pole of the oocyte nucleus. During later stages of previtellogenic growth the Balbiani body translocates as a single body towards the ooplasm periphery. The results presented indicate that Balbiani body translocation is cytoskeleton independent. Balbiani body repositioning does not result in the localization of its components to any distinct, asymmetrically situated region of the ooplasm but, instead, ends up with their even dispersion in the oocyte cortex. The Balbiani body in Pholcus does not seem to be implicated either in germ cell determination or organelle inheritance. Its homology with similar organelle accumulations in the oocytes of other species is discussed.     

Ultrastructural features of egg development in oviparae of the vetch aphid, Megoura viciae buckton

In the ovaries of the oviparous morph of the aphid, Megoura viciae, resting oocytes are located in the basal region of each germarium. During previtellogenic egg development, electron-dense spheres appear in the ooplasm. During vitellogenesis a brush border develops at the oolemma, and numerous protein and lipid-like spheres accumulate in the egg cytoplasm. Follicle cells are of two morphologically distinct types, termed 'type 1' and 'type 2' follicle cells. Unlike the more numerous 'type 1' cell, 'type 2' cells do not become patent. The acellular tunica propria exterior to follicle cell apices remains intact throughout egg development. During late vitellogenesis symbiont invasion of eggs takes place via 'receptor' cells encircling the pedicel at the posterior egg pole. These cells shrink and/or degenerate to create intercellular spaces that facilitate symbiont transmission. The end of vitellogenesis is marked by vitelline membrane formation and secretion of the chorionic layers, at which time the next egg in the ovariole undergoes final stages of previtellogenic growth and enters vitellogenesis.     

The Maturation of Oocyte Follicular Epithelium of Podarcis s. sicula Is Promoted by d-Aspartic Acid

We investigated whether the maturation of oocyte follicular epithelium of lizard is affected by d-aspartic acid (d-Asp). Our results demonstrated that d-Asp is endogenously present in the oocytes, and its distribution varies during the reproductive cycle and following intraperitoneal administration. At previtellogenesis, it is observed in the cytoplasm and nucleus of pyriform cells, in intermediate cells, in some small cells of the granulosa, in the ooplasm, and in some thecal elements. At vitellogenesis, d-Asp is localized in the proximity of the zona pellucida, in the theca, and in the ooplasm. Injected d-Asp is mainly captured by pyriform cells and ooplasm of previtellogenic oocytes, but a moderate accumulation is evident in the cytoplasm of some small granulosa cells and in the theca. d-Asp also increases the ovarian and plasmatic levels of 17β-estradiol and decreases those of testosterone. As a direct and/or indirect consequence of d-Asp, previtellogenic oocytes grow up and mature, resulting in a higher accumulation of carbohydrates in the granulosa, zona pellucida, and ooplasm, but also a reduction in the thickness of the granulosa layer and an increase of the theca stratum. Taken together, our results show that d-Asp may be related to the synchrony of reproduction, either enhancing the growth and maturation of follicular epithelium or influencing its endocrine functions. (J Histochem Cytochem 58:157–171, 2010)     

Previtellogenic and vitellogenic oocytes in ovarian follicles of cultured siberian sturgeon Acipenser baerii (Chondrostei,Acipenseriformes)

Previtellogenic and vitellogenic oocytes in ovarian follicles from cultured Siberian sturgeon Acipenser baerii were examined. In previtellogenic oocytes, granular and homogeneous zones in the cytoplasm (the ooplasm) are distinguished. Material of nuclear origin, rough endoplasmic reticulum, Golgi complexes, complexes of mitochondria with cement and round bodies are numerous in the granular ooplasm. In vitellogenic oocytes, the ooplasm comprises three zones: perinuclear area, endoplasm and periplasm. The endoplasm contains yolk platelets, lipid droplets, and aggregations of mitochondria and granules immersed in amorphous material. In the nucleoplasm, lampbrush chromosomes, nucleoli, and two types of nuclear bodies are present. The first type of nuclear bodies is initially composed of fibrillar threads only. Their ultrastructure subsequently changes and they contain threads and medium electron dense material. The second type of nuclear bodies is only composed of electron dense particles. All nuclear bodies impregnate with silver, stain with propidium iodide, and are DAPI‐negative. Their possible role is discussed. All oocytes are surrounded by follicular cells and a basal lamina which is covered by thecal cells. Egg envelopes are not present in previtellogenic oocytes. In vitellogenic oocytes, the plasma membrane (the oolemma) is covered by three envelopes: vitelline envelope, chorion, and extrachorion. Vitelline envelope comprises four sublayers: filamentous layer, trabecular layer 2 (t2), homogeneous layer, and trabecular layer 1 (t1). In the chorion, porous layer 1 and porous layer 2 are distinguished in most voluminous examined oocytes. Three micropylar cells that are necessary for the formation of micropyles are present between follicular cells at the animal hemisphere. J. Morphol. 278:50–61, 2017. ©© 2016 Wiley Periodicals,Inc.     

Oogenesis in the viviparous matrotrophic lizard Mabuya brachypoda

Oogenesis in the lizard Mabuya brachypoda is seasonal, with oogenesis initiated during May-June and ovulation occurring during July-August. This species ovulates an egg that is microlecithal, having very small yolk stores. The preovulatory oocyte attains a maximum diameter of 0.9-1.3 mm. Two elongated germinal beds, formed by germinal epithelia containing oogonia, early oocytes, and somatic cells, are found on the dorsal surface of each ovary. Although microlecithal eggs are ovulated in this species, oogenesis is characterized by both previtellogenic and vitellogenic stages. During early previtellogenesis, the nucleus of the oocyte contains lampbrush chromosomes, whereas the ooplasm stains lightly with a perinuclear yolk nucleus. During late previtellogenesis the ooplasm displays basophilic staining with fine granular material composed of irregularly distributed bundles of thin fibers. A well-defined zona pellucida is also observed. The granulosa, initially composed of a single layer of squamous cells during early previtellogenesis, becomes multilayered and polymorphic. As with other squamate reptiles, the granulosa at this stage is formed by three cell types: small, intermediate, and large or pyriform cells. As vitellogenesis progresses the oocyte displays abundant vacuoles and small, but scarce, yolk platelets at the periphery of the oocyte. The zona pellucida attains its maximum thickness during late oogenesis, a period when the granulosa is again reduced to a single layer of squamous cells. The vitellogenic process observed in M. brachypoda corresponds with the earliest vitellogenic stages seen in other viviparous lizard species with larger oocytes. The various species of the genus Mabuya provided us with important models to understand a major transition in the evolution of viviparity, the development of a microlecithal egg.     

Degeneration of germ line cells in amphibian ovary

Ogielska, M., Rozenblut, B., Augustyńska, R., Kotusz, A. 2010. Degeneration of germ line cells in amphibian ovary. —Acta Zoologica (Stockholm) 91 : 319–327 We studied the morphology of degenerating ovarian follicles in juvenile and adult frogs Rana temporaria, Rana lessonae and Rana ridibunda. Degeneration of primordial germ cells was never observed and was extremely rare in oogonia and early oocytes in a cyst phase in juveniles. Previtellogenic oocytes were rarely affected. Three main types of atresia were identified. In type I (subdivided into stages A–D), vitellogenic oocytes are digested by proliferating follicle cells that hypertrophy and become phagocytic. A – germinal vesicle shrinks, nucleoli fuse, oocyte envelope interrupts, and follicular cells hypertrophy; B – follicular cells multiply and invade the oocyte; C – entire vesicle is filled by phagocytic cells; D – degenerating phagocytes accumulate black pigment. Type II is rare and resembles breakdown of follicles and release of ooplasm. In type III, observed in previtellogenic and early vitellogenic oocytes, ooplasm and germinal vesicle shrink, follicle cells do not invade the vesicle, and condensed ooplasm becomes fragmented. The residual oogonia in adult ovaries (germ patches) multiply, but soon degenerate.     

Formation and structure of nutritive cords in telotrophic ovarioles of snake flies (Insecta: Raphidioptera)

Telotrophic ovariole of Raphidia spp. is composed of the anteriorly located terminal filament, tube-shaped tropharium, the vitellarium and the ovariole stalk. The tropharium consists of a central syncytial core surrounded by one cell thick layer of tapetum cells. Early previtellogenic oocytes differentiate at the base of tropharium. Both the oocytes and the tapetum cells are connected with the central syncytium by delicate intercellular bridges. At the onset of previtellogenic growth, the anterior parts of the oocytes become extended and form long cytoplasmic projections--nutritive cords. Each nutritive cord contains numerous microtubules that show no preferential orientation within the cord but diminishing anterior-posterior gradient of distribution. Irregular arrangement of microtubules indicates that this cytoskeletal scaffold does not play any role in directed transport within the ovariole but instead constitutes one of the elements of the structural framework of the nutritive cord. Besides microtubules, the stability of the nutritive cords in Raphidia ovarioles is maintained by the rim-shaped membrane foldings lined with microfilaments.     

东方扁虾卵子发生的超微结构

根据卵细胞的形态、内部结构特征及卵母细胞与滤泡细胞之间的关系,东方扁虾的卵子发生可划分为卵原细胞、卵黄发生前卵母细胞、卵黄发生卵母细胞和成熟卵母细胞等四个时期。卵原细胞胞质稀少,胞器以滑面内质网为主。卵黄发生前卵母细胞核明显膨大,特称为生发泡;在靠近核外膜的胞质中可观察到核仁外排物。卵黄发生卵母细胞逐渐为滤泡细胞所包围;卵黄合成旺盛,胞质中因而形成并积累了越来越多的卵黄粒。东方扁虾卵母细胞的卵黄发生是二源的。游离型核糖体率先参与内源性卵黄合成形成无膜卵黄粒。粗面内质网是内源性卵黄形成的主要胞器。滑面内质网、线粒体和溶酶体以多种方式活跃地参与卵黄粒形成。卵周隙内的外源性物质有两个来源:滤泡细胞的合成产物和血淋巴携带、转运的卵黄蛋白前体物。这些外源性物质主要通过质膜的微吞饮作用和微绒毛的吸收作用这两种方式进入卵母细胞,进而形成外源性卵黄。内源性和外源性的卵黄物质共同参与成熟卵母细胞中富含髓样小体的卵黄粒的形成。卵壳的形成和微绒毛的回缩被认为是东方扁虾卵母细胞成熟的形态学标志。