Ovarian maturation and oogenesis in the blue swimmer crab,Portunus pelagicus (Decapoda: Portunidae)

The study was aimed at understanding the process of reproduction and the changes happening in the ovary of Portunus pelagicus during maturation, which would be useful for its broodstock development for hatchery purposes. For that, tissue samples from different regions of the ovary at various stages of maturation were subjected to light and electron microscopy, and based on the changes revealed and the differences in ovarian morphology, the ovary was divided into five stages such as immature (previtellogenic oocytes), early maturing (early vitellogenic oocytes), late maturing (late vitellogenic oocytes), mature (vitellogenic oocytes), and spent (resorbing oocytes). The ovarian wall comprised of an outermost thin pavement epithelium, a middle layer of connective tissue, and an innermost layer of germinal epithelium. The oocytes matured as they moved from the centrally placed germinal zone toward the ovarian wall. The peripheral arrangement of nucleolar materials and the high incidence of cell organelles during the initial stages indicated vitellogenesis I. Movement of follicle cells toward oocytes in the early maturing stage and low incidence of mitochondria and endoplasmic reticulum in the ooplasm during late vitellogenic stage marked the commencement and end of vitellogenesis II, respectively. Yolk granules at various stages of development were seen in the ooplasm from late vitellogenic stage onwards. The spent ovary had an area with resorbing oocytes and empty follicle cells denoting the end of one reproductive cycle and another area with oogonial cells and previtellogenic oocytes indicating the beginning of the next.     

Immunolocalization of estrogen receptor α in Neomysis japonica oocytes and follicle cells during ovarian development

Estrogen induces oocytes development and vitellogenesis in crustacean by interacting with estrogen receptor (ER) subtypes. In the present study, we detect for the first time the ERα in oocytes and follicle cells and hepatopancreas cells of mysis by immunohistochemistry using a specific ERα antibody. ERα was mainly localized in the nuclei of oocytes and follicle cells, while mainly detected in nuclei of oogonia (OG), previtellogenic oocyte (PR) and endogenous vitellogenic oocyte (EN) at previtellogenic and early vitellogenic stage (I-early III). Follicle cells in all stages of ovary (all vitellogenic stages) showed strong ERα positive reaction, and they were able to gradually move to oocytes during the development of oocytes. In addition, ERα was also localized in the nuclei and cytoplasm of four hepatopancreas cells (including E-, R-, F- and B-cell) in all ovary stages. These findings suggest, for the first time to our knowledge, that there could be a close link between oogenesis, follicle cells, hepatopancreas cells and endocrine regulation, and estrogens might be involved in the regulation of oocytes at early ovarian stage in mysis.     

Ultrastructure and melatonin 1a receptor distribution in the ovaries of African ostrich chicks

Healthy 90-day-old ostrich chicks were used in the present study. The ultrastructure and melatonin 1a receptor (MT1) distribution in the ovaries of ostrich chicks was observed by transmission electron microscope and light microscope. The results showed that the ostrich chick ovary contained primordial follicles, primary follicles and secondary follicles, but no mature follicles. There are some unique ultrastructural characteristics observed in the secondary follicle, such as the cortical granule, which was located in cytoplasm beside the nucleus and appeared first in the oocyte. The zona radiata appeared in the secondary follicle, and there was an obvious vitelline membrane. There were intraovarian rete, connecting rete, and extraovarian rete in the ovaries of ostrich chicks. This is the first study that provides immunohistochemical evidence for the localization of the melatonin MT1 in the ostrich chick ovary. The germinal epithelium, follicular cell layer of every grade of follicle, cytoplasm of the oocyte and interstitial cells all expressed MT1. The expression of positive immunoreactivity materials was the strongest in the follicular cell layer of the primordial follicle and germinal epithelium, was weaker in the follicular cell layer of the primary follicle and secondary follicle, and was weakest in the oocytes of all grades of follicle. In addition, the extraovarian rete displayed strong positive expression of MT1, while there was no positive expression in the intraovarian rete or connecting rete. The positive expression of MT1 immunoreactivity in the ovary was very strong, implying that the ovary is an important organ for synthesizing MT1.     

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.     

An immunocytochemical study of pituitary cells of the Senegalese sole, Solea senegalensis (Kaup 1858)

Different antisera directed against mammalian and piscine pituitary hormones, as well as a battery of various conventional histochemical techniques (PAS, Alcian Blue pH 2.5, Bromophenol Blue) and lectins, were used to identify the different hormonal cell types in the pituitary of the Senegalese sole, Solea senegalensis. Prolactin and adrenocorticotrophic cells were located in the rostral pars distalis of the pituitary. Gonadotrophic, thyrotrophic and growth hormone cells were distributed in the proximal pars distalis, but gonadotrophic cells appear also at the border of the pars intermedia. Somatolactin cells, as well as α-melanotrophic cells were located in the pars intermedia of the Solea senegalensis pituitary. The PAS reaction was positive in somatolactin cells, which were unreactive with the lead--Haematoxylin technique, whereas melanotrophic cells were positive. Glycoproteins containing mannose and/or glucose, as well as N-acetyl-glucosamine and sialic acid sugar residues, are synthesized and secreted by gonadotrophic, thyrotrophic and somatolactin cells. Adrenocor ticotrophic cells and, especially, the amphiphilic somatolactin and acidophilic growth hormone cells were stained with the Bromophenol Blue technique that identifies proteins in general, but adrenocorticotrophic and growth hormone cells were unreactive towards PAS, Alcian Blue pH 2.5 and lectins (Con A and WGA)     

An immunocytochemical study of pituitary cells of the Senegalese sole, Solea senegalensis (Kaup 1858)

Different antisera directed against mammalian and piscine pituitary hormones, as well as a battery of various conventional histochemical techniques (PAS, Alcian Blue pH 2.5, Bromophenol Blue) and lectins, were used to identify the different hormonal cell types in the pituitary of the Senegalese sole, Solea senegalensis. Prolactin and adrenocorticotrophic cells were located in the rostral pars distalis of the pituitary. Gonadotrophic, thyrotrophic and growth hormone cells were distributed in the proximal pars distalis, but gonadotrophic cells appear also at the border of the pars intermedia. Somatolactin cells, as well as α-melanotrophic cells were located in the pars intermedia of the Solea senegalensis pituitary. The PAS reaction was positive in somatolactin cells, which were unreactive with the lead--Haematoxylin technique, whereas melanotrophic cells were positive. Glycoproteins containing mannose and/or glucose, as well as N-acetyl-glucosamine and sialic acid sugar residues, are synthesized and secreted by gonadotrophic, thyrotrophic and somatolactin cells. Adrenocor ticotrophic cells and, especially, the amphiphilic somatolactin and acidophilic growth hormone cells were stained with the Bromophenol Blue technique that identifies proteins in general, but adrenocorticotrophic and growth hormone cells were unreactive towards PAS, Alcian Blue pH 2.5 and lectins (Con A and WGA) This revised version was published online in November 2006 with corrections to the Cover Date.     

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).     

Activin incorporation into vitellogenic oocytes of Xenopus laevis.

Activin uptake into Xenopus oocytes was studied by several complementary methods. Immunocytochemistry of adult ovary localized activin and follistatin in the cytoplasm of vitellogenic oocytes and surrounding follicle cells. Surface plasmon resonance analysis of protein interaction kinetics indicated that while follistatin or a complex of activin-follistatin bound to yolk vitellogenin, activin alone did not. Radioactive tracer analysis measured specific incorporation of activin by viable oocytes in vitro. Together, the results suggest that vitellogenic oocytes can import activins from follicle cells and that follistatin may act as a chaperone for binding activin to vitellogenin in yolk platelets.     

中国大鲵闭锁卵泡的显微和超微结构观察

用光镜和电镜观察了中国大鲵卵泡闭锁过程和闭锁小体的显微和超微结构。结果显示 ,大鲵闭锁小体是卵泡细胞侵噬卵母细胞并增殖形成细胞团 ,膜细胞未参与。在大部分卵泡处于缓慢生长期时 ,未发现卵泡闭锁现象 ;在 5、 6月份 ,卵巢内大部分卵母细胞进入卵黄形成前期 ,部分卵泡闭锁 ,但闭锁小体细胞的类固醇激素分泌结构特征不明显 ;在 7、 8月份 ,大多数卵母细胞处于卵黄形成期 ,闭锁小体细胞具有管泡状嵴线粒体、丰富的滑面内质网和脂滴、发达的高尔基体等。这些细胞学特征表明闭锁小体可分泌类固醇激素 ,以调节正常卵子的成熟。在大鲵中观察到的闭锁小体属于排卵前黄体     

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.     

Morphology and ultrastructure of the somatic cells in Astacus leptodactylus ovary

We defined the somatic environment in which female germinal cells develop, and performed ultrastructural analyses of various somatic cell types, with particular reference to muscle cells and follicle cells, that reside within the ovary at different stages of oogenesis. Our findings show that ovarian wall of the crayfish is composed of long muscle cells, blood cells, blood vessels and hemal sinuses. The follicle and germinal cells lie within a common compartment of ovarian follicles that is defined by a continuous basal matrix. The follicle cells form branching cords and migrate to surround the developing oocytes. A thick basal matrix separates the ovarian interstitium from ovarian follicles compartment. Transmission electron microscopy shows that inner layer of basal matrix invaginates deeply into the ovarian compartment. Our results suggest that before being surrounded by follicle cells to form follicles, oogonia and early previtellogenic oocytes reside within a niche surrounded by a basal matrix that separates them from ovarian interstitium. We found coated pits and coated vesicles in the cortical cytoplasm of previtellogenic and vitellogenic oocytes, suggesting the receptor mediated endocytosis for transfer of material from the outside of the oocytes, via follicle cells. The interstitial compartment between the inner muscular layer of the ovarian wall and the basal matrix of the ovarian follicle compartment contains muscle cells, hemal sinuses, blood vessels and blood cells. Granular hemocytes, within and outside the vessels, were the most abundant cell population in the ovarian interstitium of crayfish after spawning and in the immature ovary. J. Morphol. 277:118–127, 2016. © 2015 Wiley Periodicals, Inc.     

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.     

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)     

Immunocytohistochemical characterization of pituitary cells of the bluefin tuna, Thunnus thynnus L

In this paper we report the first complete mapping of the pituitary in a tuna species. The various different adenohypophysis cell types of the bluefin tuna, Thunnus thynnus L. have been identified and located using different antisera against mammalian and piscine hormones and various histochemical techniques: PAS, Alcian Blue pH 2.5 and lectins -ConA and WGA(Neutral and Acidic Glycoproteins); Bromophenol Blue (Proteins) and Tioglycollate-Ferric-Ferricianide-FeIII (-S-S- groups). Prolactin (PRL) and adrenocorticotrophic (ACTH) cells were located in the rostral pars distalis (RPD) of the pituitary, while the proximal pars distalis (PPD) displayed gonadotrophic (GTH), thyrotrophic (TSH), somatotrophic (GH) and also a few PRL cells. Moreover, somatolactin (SL) and melanotrophic (MSH) cells were identified inside the pars intermedia (PI). Interestingly, some SL-immunoreactive fibers were also detected in the neurohypophysis. Some GTH cells were also located on the exterior surface of the PI. Glycoproteins containing mannose (Man) and/or glucose (Glc); N-acetyl-glucosamine (GlcNAc) and/or sialic acid sugar residues, as well as -S-S- groups, were observed in GTH, TSH and SL cells. The Bromophenol Blue technique stained amphiphilic SL, acidophilic GH cells and weakly ACTH cells. GH and ACTH cells were unreactive to PAS, Alcian Blue, Tioglycollate-Ferric-Ferricianide-FeIII and lectin (Con A and WGA) techniques. Finally, PAS reaction was positive in amphiphilic SL cells, which were PbH unreactive, while MSH and ACTH cells were stained with PbH technique.     

Mechanisms of maternal inheritance of dinoflagellate symbionts in the acoelomorph worm Waminoa litus

Waminoa litus is a zooxanthella-bearing acoel worm that infests corals. It is unique to Bilateria in that it transmits its algal symbionts vertically via eggs irrespective of the heterogeneity of the symbionts. It simultaneously harbors two dinoflagellate genera: Symbiodinium and Amphidinium. In this study, we examined the timing and vertical transmission pathway of algal symbionts in W. litus using light and electron microscopy. The oogenesis of the worm can be divided into three stages: stage I, in which the ovary is absent; stage II, the early vitellogenic zone containing immature oocytes formed in the ovary; and stage III, with both early and late vitellogenic zones in the body. In the early vitellogenic zone at stage II, oocytes are surrounded by accessory-follicle cells (AFCs). Both Symbiodinium and Amphidinium symbionts are not initially observed in the oocytes, but are observed in the AFCs. In the late vitellogenic zone at stage III, oocytes are enveloped by a complete sheath of AFCs; the algal symbionts are taken up by the late vitellogenic oocytes. These observations suggest that AFCs mediate the transfer of the algae from the parent to the oocytes. Ribotype analyses of the Symbiodinium symbionts revealed that they differ from those harbored by coral in the same experimental aquarium. These results indicate that W. litus has an active algal transport pathway and maintains a specific lineage of Symbiodinium via vertical transmission.     

南方鲶卵巢滤泡细胞和卵膜生成的组织学研究

南方鲶的卵巢滤泡细胞源于卵巢基质细胞,从发生到退化分为零散卵泡膜细胞期、单层扁平泡膜细胞期、多层扁平卵泡膜细胞期、立方形颗粒细胞期柱状颗粒细胞期、颗粒细胞分泌期和颗粒细胞退化期。精孔细胞中发育中滤泡细胞分化形成。初级卵精源于卵母细胞,次级卵膜由晚期滤泡细胞分泌形成。本文还对滤泡细胞和卵膜的作用进行了阐述。     

Oogenesis of Mozambique tilapia. IV. Yolk formation

Yolk globules in developing oocytes of Tilapia mosambique are formed by two processes: 1) biosynthetical activity of oocyte organoides; 2) vitellogenin migration by micropinocytosis and its further transformation. Undoubtedly, yolk globules of endogenic and exogenic origin are fused. The primary yolk globules are spherical, and the secondary ones are lobular. The latter originate by incorporating the former. The fast growth of the late vitellogenic stage oocytes occurs as a result of active migration of primary yolk globules into the central part of the oocyte and as their association with the secondary yolk globules. In vitellogenic oocytes of T. mosambique no yolk vesicles (cortical granules), were found by any existing methods.     

Histomorphological and histochemical characteristics of the intestine of the Senegal sole, Solea senegalensis.

The Senegal sole, Solea senegalensis has been exploited extensively in aquaculture from different countries; at present an intensive production of larvae and adults is being achieved with some nutritional problems. Since this species displays very different life styles and feeding habits at different stages of its life history (larvae, metamorphosis, adults), and because digestive mucins are implicated in different physiological processes including: increase of digestive efficiency, promotion of macromolecules-absorption, buffering of intestinal fluid, prevention of proteolytic damage to the epithelium and defence against bacteria, etc., we studied the histomorphological aspects, as well as the histochemical distribution of carbohydrates, (PAS, Alcian Blue), proteins (Bromophenol Blue), lipids (Oil Red O, Black Sudan B) and glycoproteins (Horseradish peroxidase-conjugated lectins) in the intestinal epithelium of adult Solea senegalensis specimens. Our data are compared with those obtained in larvae and adults of this and other fish species. Primary and secondary folds, microvilli of the intestinal enterocytes, as well as mucous or goblet cells were observed with a scanning electron microscope. Enterocytes and mucocytes of the intestine of adult Solea senegalensis were characterized by a rich supply of sugar and oligosaccharides. Carbohydrates (glycogen and mucins), proteins and lipids were present in cytoplasm and microvilli--brush border--of the enterocytes, which contain GalNAc, GlcNAc, Man, Glc and sialic acid-N-acetyl-D-galactosamine glycoconjugates. Intestinal mucous cells were strongly or weakly stained with Alcian Blue (pH 2.5 and 1). PAS reactivity was intense in numerous goblet cells, but some cells were PAS unreactive or weakly stained. Some goblet cells were positive for Bromophenol Blue but numerous cells were unstained; thus many proteins and possibly lipids may be conjugated with sugars. A similar reactivity to WGA and to neuraminidase-WGA was identified in some intestinal goblet, which were Con A unreactive, indicating the absence of Man and/or Glc and NANA glycoconjugates. GalNAc residues were only scarcely present in glycoproteins of some goblet cells.