Yolk formation in Isohypsibius (Eutardigrada)

Summary In Isohypsibius granulifer, yolk is autosynthesized. The Golgi apparatus is mainly responsible for the formation of yolk, which consists of irregular platelets with heterogeneous contents and a diameter of about 1 m. Dense globules, 300 nm in diameter, are visible among yolk platelets. These develop in the vesicles of the rough endoplasmic reticulum. The genesis of these vesicles is associated with the outer membrane of the nuclear envelope, which forms blebs intensively during previtellogenesis and early vitellogenesis. The developing oocytes are assisted by nurse cells, to which they are jointed by cytoplasmic bridges. For every oocyte, there are a number nurse cells, which are sister cells of the oocyte. In addition to rRNA, nurse cells transfer to the oocyte lipids, platelets of yolk formed in their cytoplasm, mitochondria and cortical granules.     

Ultrastructural observations of the early and late stages of gorgonian coral (Junceella juncea) oocytes

The developmental oogenesis of gorgonian coral was investigated at the histological level. The objective of this study was to examine and improve the understanding of Junceella juncea oogenesis using ultrastructural methods, such as histological sectioning and transmission electron microscopy. At least three types of yolk materials were observed in this study: yolk body, lipid granules and cortical alveoli. Some of the complex yolk materials were encompassed by concentric or arched layers of smooth and rough endoplasmic reticulum and the Golgi complex in early stage oocytes. Different types of vesicles were found in both early and late stage oocytes and some granules could be seen inside the empty vesicles. This may be a possible method for elaborating complex yolk materials. Homogeneous yolks from different types of inclusions were abundant and the autosynthesis of yolk may be a major mechanism in J. juncea oocytes. This is the first report of the ultrastructural observation of oogenesis in gorgonian coral species using transmission electron microscopy. Our study obtained relatively detailed information at the ultrastructural level, and it provides an overview of the oocyte ultrastucture of the gorgonian coral J. juncea.     

Oogenesls in the terrestrial hermit crab,coenobita clypeatus (decapoda,anomura): II. Vitellogenesis

Oocytes from the land hermit crab, Coenobita clypeatus, in various stages of vitellogenesis were examined by light and electron microscopy. Early vitellogenic oocytes are characterized by accumulations of discrete vesicles of endoplasmic reticulum in the perinuclear cytoplasm. As oocytes develop, the endoplasmic reticulum becomes abundant, and numerous Golgi complexes are seen. There is a well developed Golgi-endoplasmic reticulum interaction. Within the confines of the reticulum are discrete intracisternal granules, which can be seen coalescing into electron-dense yolk bodies. Lipid accumulation is seen throughout the cytoplasm. Coincident with the burst of intra-oocytic metabolism are oolemma modifications and micropinocytosis, which provide ultrastructural evidence for extra-oocytic yolk production. The mature oocyte contains numerous yolk and lipid vesicles of varying electron density that comprise both intra- and extra-oocytic substrates.     

Yolk formation in an annelid (Ophryotrocha puerilis, polychaeta)

The polychaete Ophryotrocha does not show a distinct breeding season. Egg masses are produced throughout the year (continuous breeder sensu Olive and Clark, 1978). A female specimen may contain up to three different generations of oocytes with oocyte growth and maturation in each batch being well synchronized. Oogenesis takes about 18 days from proliferation of the oogonia to mature eggs. In each segment pairs of sister cells interconnected by cytoplasmic bridges are located in outpocketings of the ventral mesentery which form the gonad wall. Presumptive oocytes and nurse cells are not easily distinguished at that time. Vitellogenesis is initiated while both oocytes and nurse cells are still in the ovary. Mitochondria, multivesicular bodies (transformed mitochondria ?), dense bodies, preformed yolk bodies of smaller size and lipid droplets are probably passed through the cytoplasmic bridge from the nurse cell to the oocyte. Yolk formation includes different mechanisms and materials of different origin. Autosynthetic yolk formation predominates during the first intraovarial growth phase. After detachment of oocyte-nurse cell-complexes from the gonad pinocytotic activity of nurse cells and particularly oocytes, increases considerably. The existence of coated vesicles suggests that external sources of yolk precursors contribute to yolk formation. Prior to oocyte maturation the remnants of the nurse cell are incorporated by oocytes.     

Fine Structure of the Ovarian Development in the Orb-web Spider, Nephila clavata

ABSTRACT Fine structural changes of the ovary and cellular composition of oocyte with respect to ovarian development in the orb-web spider, Nephila clavata were examined by scanning and transmission electron microscopy. Unlike the other arthropods, the ovary of this spider has only two kinds of cells-follicle cells and oocytes. During the ovarian maturation, each oocyte bulges into the body cavity and attaches to surface of the elongated ovarian epithelium through its peculiar short stalk attachments. In the cytoplasm of the developing oocyte two main types of yolk granules, electron-dense proteid yolk and electron-lucent lipid yolk granules, are compactly aggregated with numerous glycogen particles. The cytoplasm of the developing oocyte contains a lot of ribosomes, poorly developed rough endoplasmic reticulum, mitochondria and lipid droplets. These cell organelles, however, gradually degenerate by the later stage of vitellogenesis. During the active vitellogenesis stage, the proteid yolk is very rapidly formed and the oocyte increases in size. However, the micropinocytosis invagination or pinocytotic vesicles can scarcely be recognized, although the microvilli can be found in some space between the oocyte and ovarian epithelium. During the vitellogenesis, the lipid droplets in the cytoplasm of oocytes increase in number, and become abundant in the peripheral cytoplasm close to the stalks. On completion of the yolk formation the vitelline membrane, which is composed of an inner homogeneous electron-lucent component and an outer layer of electron-dense component is formed around the oocyte.     

Histological and histochemical study of female germ cell development in the dusky grouper Epinephelus marginatus (Lowe, 1834)

The developmental stages of female germ cells were analysed in a wild population of the protogynous teleost Epinephelus marginatus (Lowe, 1834). 321 wild dusky grouper females were collected in the South Mediterranean Sea during the spawning season and their ovaries analysed using histological and histochemical techniques. Oocyte morphology, nucleus-cytoplasm ratio (N/C) range, location and movements of cytoplasmic inclusions during primary growth, vitellogenesis and final oocyte maturation were described. The distribution of proteins, lipids and carbohydrates through oocyte development was also investigated in 50 females. Lipid vesicles appeared firstly in the mid ooplasm of oocytes larger than 130 microm, at the beginning of the secondary growth phase. Immediately afterwards, small carbohydrate granules (PAS and Alcian blue positive) appeared before the occurrence of the first yolk granules. Tyrosine-enriched proteins were especially evidenced in the zona radiata interna of late vitellogenic oocytes. Specific lectin binding patterns reflected characteristic differences in the content and distribution of specific sugar moieties expressed in the oocytes during vitellogenesis and final maturation. At the end of vitellogenesis and during final maturation, follicular cells, zona radiata, and cortical alveoli were characterised by a strong increase of specific binding for WGA.     

Ultrastructural study of oogenesis in Phoronopsis harmeri (Phoronida)

Temereva, E.N., Malakhov, V.V. and Yushin, V.V. 2011. Ultrastructural study of oogenesis in Phoronopsis harmeri (Phoronida). —Acta Zoologica (Stockholm) 92 : 241–250. The successive stages of oogenesis in Phoronopsis harmeri were examined by electron microscopy methods. During the oogenesis, each oocyte is encircled by vasoperitoneal (coelomic) cells forming a follicle. The previtellogenic oocytes are small cells which accumulate ribosomes for future synthesis; their cytoplasm contains characteristic clusters of mitochondria and osmiophilic particles resembling a germ plasm of other metazoans. The cytoplasm of the vitellogenic oocytes includes numerous mitochondria, cisternae of the rough endoplasmic reticulum, Golgi bodies and annulate lamellae. The synthesis of three types of inclusions was observed: strongly osmiophilic granules (lipid droplets) as a prevalent component, distinctly larger granules surrounded by membrane (proteinaceous yolk) and numerous large vesicles with pale flocculent content. No inclusions which could be unequivocally interpreted as the cortical granules were detected. The surface of the vitellogenic oocytes is covered by microvilli which increase in number and length during development. The oogenesis in Phoronida may be interpreted as follicular because of close association of oocytes with the vasoperitoneal tissue. However, well‐developed synthetic apparatus together with a strongly developed microvillous surface and absence of endocytosis indicate a clear case of autosynthetic vitellogenesis. Thus, in phoronids, there is a combination of simply developed follicle and autosynthesis that, apparently, is plesiomorphic character.     

Ovarian Structure in Milnesium tardigradum (Tardigrada, Milnesiidae) during Early Vitellogenesis

The ultrastructure of the ovary of Milnesium tardigradum during early vitellogenesis is described. Within the ovary, there were large multinuclear cells surrounded by many mononuclear oocytes. Observation of serial sections revealed four multinuclear cells that were connected to each other by cytoplasmic bridges. Each peripheral oocyte was connected to the multinuclear cell. An enormous ER-like structure was conspicuous in the centre of the multinuclear cell. The presence of large numbers of lipid droplets and yolk granules in both multinuclear cells and many mononuclear oocytes suggested a role as nurse cells. A small number of these oocytes grow to be eggs. The structural features of the multinuclear nurse cell were compared with other known examples.     

莫桑比克非鲫卵黄形成的电镜观察

运用透射电镜观察了莫桑比克非鲫卵母细胞的生长.根据卵母细胞的大小和内部结构特征,将其分为四个时期:卵母细胞生长早期:卵黄泡形成期:卵黄积累期:卵黄积累完成期.本文着重研究了主要卵黄成分--卵黄球的形成过程.卵黄球属外源性卵黄,由卵母细胞通过微胞饮作用吸收肝脏合成的卵黄蛋白原后形成的.在卵黄大量积累前,卵母细胞内的线粒体和多泡体聚集成团,构成卵黄核,继而线粒体大量增殖,线粒体形状发生改变,形成同心多层膜结构,为大量的卵黄物质积累提供场所.最终形成的卵黄球由被膜、卵黄结晶体和两者之间的非结晶区三部分组成.       

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。       

Do fast increasing food conditions promote the midsummer decline of Daphnia galeata?

Ovaries from mature giant red shrimp Aristaeomorpha foliacea were investigated histochemically and ultrastructurally. Four growing stages of the oocytes were distinguished: premeiosis stage, previtellogenetic stage, early vitellogenic stage and late vitellogenic stage. In addition, occasional resorptive oocytes were found. Oogonia and premeiotic oocytes were found in germinative zones. Previtellogenic and vitellogenic oocytes were localized in maturative zones. As vitellogenesis proceeded, oocytes showed a progressive development in the number of lipid droplets as well as in the extension of RER, constituted of dilated cisternae, uniformely scattered throughout the cytoplasm. The RER produced yolk granules and a lampbrush-like substance. The latter was released under the oolemma and constituted a characteristic cortical zone. The oolemma did not develop microvilli or micropinocytotic vesicles to incorporate yolk precursors. Thus, the protein yolk appeared to be of endogenous origin. Few somatic cells were found around the oocytes, but they never gave place to a continuous epithelial layer around oocytes, thus it is not possible to speak of ovarian follicle. The cytoplasm of these mesodermal-oocyte associated cells (MOAC) was characterized by a typical steroidogenic apparatus. Few resorptive immature oocytes were found inside late vitellogenic oocytes. Since the ovaries were packed with late vitellogenic oocytes and the few immature oocytes were hardly detectable, oocyte maturation occurred in a synchronous way.     

Annual Cyclical Changes in the Histological Features and Surface Ultrastructure in Ovaries of the Freshwater Featherback Notopterus notopterus (Pallas, 1769)

The feather back, Notopterus notopterus is an important food fish. Its ovary is an extremely dynamic organ and the oocytes present an asynchronous development. Variations in ovary weight, GSI, diameter of oocytes were studied in different months of the year in this fish. Different developmental stages of female germ cells were identified on the basis of histological and ultrastructural characteristics in the ovary of N. notopterus (Pallas). In the present investigation the oocyte development of N. notopterus was divided into five stages (oogonia, perinucleolar oocyte, cortical alveolus, yolk granules stage and mature oocyte). The cytophysiological features like vitellogenesis, chorion formation and atresia of some follicles were also studied in the present investigation. The seasonal changes in the ovary have been described according to the variations in gonadosomatic index and the cytological changes of the female germ line cells.     

Follicular cells of the amphibian ovary: Origin, structure, and functions

Formation of the follicular envelopes surrounding oocytes in the developing ovary and their subsequent morphological differentiation go hand-in-hand with succession of the steroidogenesis stages, arrest of meiosis and its maintenance, establishment of the conditions necessary for vitellogenesis, oocyte growth, and maturation. Metabolites are exchanged via gap junctions and receptor-mediated transport through the perioocytic space. The ion transport in follicular cells (FCs) regulates the plasma membrane potential, creating the conditions for efficient directed transport through gap junctions. Manifold biologically active substances accepted by follicular cells are an additional adjusting lever for regulating the state of follicle system. In this review, we have attempted to emphasize the amphibian FCs as key players in the follicle system; the more so as we have failed to find any review that would bring together the data on the origin of amphibian FCs, their morphology, as well as regulation of oocyte growth and development. As a rule, recent works in this field focus on the molecular mechanisms providing for regulation of individual stages in oocyte development. This review describes the origin and changes in the morphology of follicular cells during the development of Xenopus laevis oocyte as well as the data on their regulatory functions in vitellogenesis and their involvement in steroidogenesis, maintenance of meiotic arrest, and subsequent maturation.     

The development of oocytes in the ovary of a parthenogenetic tick, Haemaphysalis longicornis

Haemaphysalis longicornis is an important vector of various pathogens in domestic animals and humans. The tick is a unique species with bisexual and parthenogenetic races. Although mating induces oocyte development, it is possible in the parthenogenetic race to complete oogenesis without copulation. Here we examined the developmental process of oocytes from unfed to the oviposition period in parthenogenetic H. longicornis. We classified the developmental stages of oocytes into five stages: stage I, germinal vesicle occupies more than half of the cytoplasm; stage II, germinal vesicle occupies less than half of the cytoplasm; stage III, germinal vesicle migrates from the center in the oocyte to the vicinity of the pedicel cells; stage IV, the cytoplasm is filled with yolk granules of various sizes; stage V, the cytoplasm is occupied by large yolk granules. Oocytes at the unfed period were undeveloped and classified as stage I. Stage I and II oocytes were observed at the rapid feeding period, indicating that oocyte development began after the initiation of blood feeding. All developmental stages of oocytes were observed at the pre-oviposition period. At 10?days after the beginning of the oviposition period, the ratios of stage I and II oocytes were higher than those of the previous period, suggesting that the ovarian development and activity may be continuing. Based on these findings, we propose classification criteria for the oocyte development in the parthenogenetic H. longicornis. The criteria will be useful for understanding the mechanisms of tick reproduction and transovarial transmission of pathogens.     

Morphology and ultrastructure of the adult ovarian cycle in Mithracidae (Crustacea,Decapoda, Brachyura,Majoidea)

The ultrastructure of the ovary during development and yolk production is poorly known in Brachyura and Majoidea in particular. Here, we describe the histology, histochemistry and ultrastructure of the adult ovarian cycle in four Mithracidae species from three different genera: Mithrax hispidus, Mithrax tortugae, Mithraculus forceps and Omalacantha bicornuta. All species showed a similar pattern of ovarian development and vitellogenesis. Macroscopically, we detected three stages of ovarian development: rudimentary (RUD), developing (DE) and mature (MAT); however, in histological and ultrastructural analyses, we identified four stages of development. The oocytes of the RUD stage, during endogenous vitellogenesis, have basophilic cytoplasm filled with dilated rough endoplasmic reticulum. The reticulum lumen showed many granular to electron-dense materials among the different stages of development. The Golgi complexes were only observed in the RUD stage and are responsible for releasing vesicles that merge to the endogenous or immature yolk vesicles. At the early DE stage, the oolemma showed many coated and endocytic vesicles at the cortex. The endocytic vesicles merge with the endogenous yolk to form the exogenous or mature yolk vesicles, always surrounded by a membrane, characterizing exogenous vitellogenesis. The exogenous yolk vesicles comprise glycoproteins, showing only neutral polysaccharides. At the late DE stage, endocytosis still occurs, but the amount of endogenous yolk decreases while the exogenous yolk increases. The late DE stage is characterized by the beginning of chorion production among the microvilli. The MAT stage is similar to the late DE, but the endogenous yolk is restricted to a few cytoplasmic areas, the ooplasma is filled with exogenous yolk, and the oolemma has very few coated vesicles. In the MAT stage, the chorion is fully formed and shows two electron-dense layers. The ovarian development of the species studied has many similarities with the very little known Majoidea in terms of the composition, arrangement and increment of the yolk vesicles during oocyte maturation. The main differences are in the vitellogenesis process, where immature yolk formation occurs without the direct participation of the mitochondria but with the participation of the rough endoplasmic reticulum in the endogenous phase.     

STEROID INHIBITION OF PROTEIN INCORPORATION BY ISOLATED AMPHIBIAN OOCYTES

The relationship between blood protein (vitellogenin) incorporation and nuclear maturation was studied in individual amphibian oocytes after in vitro exposure to desoxycorticosterone acetate (DOCA). Isolated Rana pipiens oocytes were incubated in vitro with radioactively labeled oocyte yolk precursor ([³H]vitellogenin) obtained from estrogenized Xenopus laevis. Incorporation of labeled vitellogenin into the oocytes continued over a 24-h period. Oocytes simultaneously exposed to DOCA and to labeled vitellogenin exhibited both inhibition of vitellogenin incorporation and stimulation of nuclear maturation and cortical changes. Inhibition of vitellogenin incorporation was observed after approximately 9 h of incubation and was correlated with the time of nuclear breakdown. Preincubation of oocytes in steroid for 9 h essentially terminated vitellogenin incorporation. Incorporation of vitellogenin occurred after removal of follicle cells from the oocyte by a short treatment with EDTA. These results demonstrate the macromolecular vitellogenin transport system remains operative in oocytes which can undergo nuclear maturation and that the steroid DOCA can affect its function. Evidence suggests that the mechanism of steroid inhibition is in part the result of inhibition of the micropinocytotic process in the oocyte cortex.     

Oogenesis in the bluefin tuna,Thunnus thynnus L.: a histological and histochemical study

Histology and histochemistry are useful tools to study reproductive mechanisms in fish and they have been applied in this study. In the bluefin tuna, Thunnus thymus L., oocyte development can be divided into 4 principal phases based on the morphological features of developing oocytes and follicles. The primary growth phase includes oogonia and basophilic or previtellogenic oocytes classified as chromatin-nucleolus and perinucleolus stages. The secondary growth phase is represented by vitellogenic oocytes at early (lipid globule and yolk granule 1), mid (yolk granule 2) and late (yolk granule 3) vitellogenesis stages. The maturation phase involves postvitellogenic oocytes undergoing maturation process. During the spawning period, both postovulatory follicles, which indicate spawning, and atretic follicles can be distinguished in the ovary. Carbohydrates, lipids, proteins and specially those rich in tyrosine, tryptophan, cystine, arginine, lysine and cysteine, as well phospholipids and/or glycolipids and neutral glycoproteins were detected in yolk granules. Moreover, affinity for different lectins (ConA, WGA, DBA and UEA) was detected in vitellogenic oocytes (yolk granules, cortical alveoli, follicular layer and zona radiata), indicating the presence of glycoconjugates with different sugar residues (Mannose- Man- and/or Glucose -Glc-; N-acetyl-D-glucosamine- GlcNAc- and/or sialic acid- NANA-; N-acetyl-D-galactosamine- GalNAc-; L-Fucose -Fuc-). Histochemical techniques also demonstrated the presence of neutral lipids in globules (vacuoles in paraffin sections) and neutral and carboxylated mucosubstances in cortical alveoli. By using anti-vitellogenin (VTG) serum, immunohistochemical positive results were demonstrated in yolk granules, granular cytoplasm and follicular cells of vitellogenic oocytes. Calcium was also detected in yolk granules and weakly in follicular envelope. In females, the gonadosomatic index (GSI) increased progressively from May, during early vitellogenesis, until June during mid and late vitellogenesis, where the highest values were reached. Subsequently, throughout the maturation-spawning phases (July), GSI decreased progressively reaching the minimal values during recovering-resting period (October).     

Maturity and gonad changes of Oreochromis (Nyasalapia) karongae raised in fish ponds in Malawi

The reproductive biology of pond-raised Oreochromis (Nyasalapia) karongae was investigated. Gonad histology and gonadosomatic indices (GSIs) indicated a potential for multiple spawning in a season. Several peaks of oocyte-size distribution and several maturation stages occurred in the same gonad. GSIs of 2.5% and 1.4% were recorded in female and male fish, respectively. Three stages of oocyte maturation (primary growth, formation of yolk vesicles, vitellogenesis) and three stages of sperm development (spermatogonia, spermatid, spermatozoa) were observed. With the exception of the final maturation stage, all development phases seemed to proceed satisfactorily. The final stage of maturation was attained at oocyte size of 2.70 ± 0.54 mm and was selectively impaired in some female fish by a lack of deposition of vitellogenin. This abnormal condition led to atrophic oocytes lacking yolk granules and vesicles. Sexual maturation was attained at a relatively large size of 16.0 cm (114 g) compared with other tilapia of the mossambicoid group (i.e. Oreochromis mossambicus and Oreochromis shiranus ). A combination of gravimetric and histological techniques was successful in charting gonad changes and calibrating external against internal gonad features.     

Ultrastructure of the ovary and oogenesis in the polychaete Capitella jonesi (Hartman, 1959)

Ultrastructural features of the ovary and oogenesis in the polychaete Capitella jonesi (Hartman, '59) have been described. The ovaries are paired, sac-like follicles suspended by mesenteries in the ventral coelom throughout the midbody region of the mature worm. Oogenesis is unsynchronized and occurs entirely within the ovary, where developing gametogenic stages are segregated spatially within a germinal and a growth zone. Multiplication of oogonia and differentiation of oocytes into the late stages of vitellogenesis occur in the germinal region of the ovary, whereas late-stage vitellogenic oocytes and mature eggs are located in a growth zone. Follicle cells envelop the oocytes in the germinal zone of the ovary and undergo hypertrophy and ultrastructural changes that correlate with the onset of vitellogenesis. These changes include the development of extensive arrays of rough ER and numerous Golgi complexes, formation of microvilli along the surface of the ovary, and the initiation of extensive endocytotic activity. Oocytes undergo similar, concomitant changes such as the differentiation of surface microvilli, the formation of abundant endocytotic pits and vesicles along the oolemma, and the appearance of numerous Golgi complexes, cisternae of rough ER, and yolk bodies. Yolk synthesis appears to occur by both autosynthetic and heterosynthetic processes involving the conjoined efforts of the Golgi complex and rough ER of the oocyte and the probable addition of extraovarian (heterosynthetic) yolk precursors. Evidence is presented that implicates the follicle cells in the synthesis of yolk precursors for transport to the oocytes. At ovulation, mature oocytes are released from the overy after the overlying follicle cells apparently withdraw. Bundles of microfilaments within the follicle cells may play a role in this withdrawal process.     

Cytochemical characterization of the endomembranous system during oocyte secondary growth in Serrasalmus spilopleura (Teleostei, Characiformes, Characidae)

The endomembranous system of Serrasalmus spilopleura oocyte secondary growth was analysed using structural and ultrastructural cytochemical techniques. In vitellogenic oocytes, the endoplasmic reticulum components, the nuclear envelope intermembranous space, some Golgi dictiossomes, lysosomes, yolk granules, regions of the egg envelope and sites of the follicle cells react to acid phosphatase detection (AcPase). The cortical alveoli, some heterogeneous cytoplasmic structures, regions of the egg envelope, and sites of the follicle cells are strongly contrasted by osmium tetroxide and zinc iodide impregnation (ZIO). The endoplasmic reticulum components, some vesicles, and sites of the follicle cells also react to osmium tetroxide and potassium iodide impregnation (KI). The biosynthetic pathway of lysosomal proteins, such as acid phosphatase, required for vitellogenesis, involves the endoplasmic reticulum, Golgi complex, vesicles with inactive hydrolytic enzymes, and, finally, lysosomes. In S. spilopleura oocytes at secondary growth, the endomembranous system takes part in the production of the enzymes needed for vitellogenesis, and in the metabolism of yolk exogenous components (AcPase detection). The endomembranous system compartments also show reduction capacity (KI reaction) and are involved in the metabolism of proteins rich in SH‐groups (ZIO reaction).