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.     

Changes in progesterone levels and distribution of progesterone receptor during vitellogenesis in the female mud crab (Scylla paramamosain)

Vertebrate-type steroids, such as progesterone, have been identified in crustaceans. The physiological activity of progesterone during vitellogenesis is still not well understood. In this study, progesterone levels in the female mud crab, Scylla paramamosain, were determined by enzyme-linked immunosorbent assay. Peak levels of progesterone were detected during the previtellogenic stage in the hemolymph, ovary, and hepatopancreas, whereas the progesterone level decreased significantly in vitellogenic stage I. During vitellogenic stage II, progesterone levels rose again in the hemolymph and ovary, but continued to decrease in the hepatopancreas. By using western blotting, progesterone receptor (PR), with an apparent molecular weight of 70 kDa, was identified in the ovary during both vitellogenic stages I and II. By means of immunohistochemistry, PR was detected mainly in the follicle cells during vitellogenic stage I and in the nuclei of oocytes in vitellogenic stage II. Our results strongly suggest that progesterone promotes vitellogenesis in the mud crab, S. paramamosain via a classical genomic mechanism.     

Fibroblast Growth Factor May Regulate the Initiation of Oocyte Growth in the Developing Ovary of the Medaka, Oryzias latipes

The distribution of fibroblast growth factor (FGF) was investigated in developing and matured ovaries of the medaka, Oryzias latipes. In the fry, FGF localized in the cytoplasmic region of all oocytes in the ovary at the pre-vitellogenic stage. Before the initiation of vitellogenesis, it disappeared in the cytoplasmic region and newly appeared around each oocyte, and then it localized around all oocytes in the ovary at the vitellogenic stage. Interestingly, the change in FGF distribution was orderly occurring from the posterior to anterior region of the ovary. In the adult, FGF was detected by immunofluorescence staining around the oocytes. These results suggest that FGF plays a significant role in the initiation of oocyte development through follicle cells, and the expression of FGF is rigidly regulated in the developing ovary of O. latipes.     

Temporal events of gypsy moth vitellogenesis and ovarian development

Abstract The vitellogenic period of gypsy moth ovarian development starts on day 3 of the pupal stage and continues through adulthood. During this period, rapid increases occur in follicle size, protein content, and wet weight of the ovary. Patency is observed on day 3 of the pupal stage.
Pre-vitellogenic follicles are formed in the last larval stadium. Newly formed follicles detach from the germarium on day 4, and increase rapidly to 140 per ovariole at the end of the last larval stadium. The pre-vitellogenic follicles are uniformly around 50 um in diameter. No vitellogenin is incorporated into the oocytes until the pupal stage.
Polyacrylamide gel electrophosesis (PAGE) in the presence of sodium dodecylsulphate (SDS) analysis of male and female haemolymph samples and vitellogenic ovaries demonstrates the presence of two female-specific subunits of vitellogenin of 180 kD and 160 kD. These proteins are detected only in haemolymph and ovarian extracts of vitellogenic females. The molecular weight of the native protein determined by size exclusion chromatography is approximately 400–420 kD.
A highly sensitive double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed to monitor the temporal changes in vitellogenin titre in haemolymph. Vitellogenin production starts on day 2 of the last larval stadium, reaching a maximum level by day 6 of the last larval stadium, and decreasing in the late pupal stage as vitellogenin was internalized into the oocytes. This is the first report of vitellogenin production occurring in the larval stage of a holometabolous insect. The fact that vitellogenin production and uptake occur during different stages of development in the gypsy moth, opens up some interesting questions concerning the underlying regulatory mechanisms controlling each process.     

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.     

Juvenile Hormone titre and vitellogenin gene expression related to ovarian development in primary reproductives compared with nymphs and nymphoid reproductives of the termite Reticulitermes speratus

To elucidate the reproductive cycle of termite queens, incipient colonies of Reticulitemes speratus (Isoptera: Rhinotermitidae) are established under laboratory conditions, and the transition of colony development is observed at 0.5, 1.5, 2.5, 3.5, and 7.5 months (stages I–V, respectively) after colony foundation. Ovarian development, vitellogenin gene expression and Juvenile Hormone (JH) titres are examined in the queens and in nonphysogastric nymphoids collected from natural colonies. A reproductive cycle in queens is observed, in which the oviposition rate is relatively higher during stages I and II, and then decreases during stages III and IV. Vitellogenic oocytes are not observed in the ovaries during stages III and IV, and the expression level of the vitellogenin gene is low, suggesting that egg production in queens is repressed during these stages. However, vitellogenin gene expression and egg deposition in queens resumes during stage V. Juvenile Hormone levels rise during the transition from nymphs to stage I queens, and elevated JH titres are observed also during stages III and IV. The decrease in JH titre in queens at stage II precedes the decline in vitellogenesis at stages III and IV. Thus, JH titre and vitellogenesis are correlated in an offset pattern. However, nonphysogastric nymphoid reproductives do not have vitellogenic oocytes in their ovaries, and their JH titre is two‐fold higher than that of queens, suggesting that elevated JH titre precedes vitellogenesis, as in queens.     

Onset of vitellogenin production and vitellogenesis,and their relationship to changes in the midgut epithelium and oocytes in the tickDermacentor variabilis

InDermacentor variabilis (Say), the onset of vitellogenin production and vitellogenesis (up-take of vitellogenin into oocytes) began during the rapid-engorgement feeding period. Mating was required for both vitellogenin production and vitellogenesis to complete the tick's life cycle. Complete immunological identity, as measured by Ouchterlony's double diffusion test, existed between vitellogenin from the fat body, midgut and hemolymph, and vitellin from the ovaries and eggs. Antivitellin antibody did not react with host hemoglobin nor with fat body, midgut, and ovary extracts from feeding females prior to rapid engorgement, feeding unmated females, or unfed or fed males. Some unmated females fed for 13 days and then hand-detached from the host eventually began oviposition after going through a preoviposition period. In these ticks, organ extracts from the midgut, fat body and ovary reacted with antivitellin antibody. The presence or absence of presumed vitellogenic cells in the midgut and yolk bodies in oocytes corresponded with the presence or absence of vitellogenin and vitellogenesis as measured by Ouchterlony's test. Presumed vitellogenic cells increased in size during the preoviposition period. These cells reached their greatest size during the time when the most eggs were being produced, and then declined in size toward the end of oviposition. Vitellogenin was deposited directly into developing yolk bodies in oocytes and was not processed through lysosomes. Feeding was the process that initiated the formation of eggshell cuticle. Detachment from the host was required for the initiation of oviposition.     

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)     

Morphology of the female reproductive system and reproductive cycle of the mangrove land crab Ucides cordatus (L.) in the Baía de Antonina,Paraná, Brazil

Ucides cordatus is a species of considerable ecological and socioeconomic importance. The goal of this study is to contribute to the understanding of the reproduction biology of this species by describing the macroscopic anatomy, the histology of the female reproductive system and the reproductive cycle of U. cordatus. A total of 367 females were obtained from October of 2002 to March of 2005 during monthly collections in the Baía de Antonina, Paraná, Brazil. Specimens were submitted to necropsy and their reproductive systems (ovary and spermathecae) were analysed histologically. Permanent slides were stained with Harris' hematoxylin and eosin, Mallory's trichromic and the periodic acid‐Schiff reaction. Ovarian analysis allowed for the determination of five developmental stages based on the prevalence of oocytes in different phases of vitellogenesis. During stage V, when ovaries recover from spawning, the presence of oocytes in advanced stages of vitellogenesis was detected, suggesting that there could be more than one spawning in a single reproductive period. Females in stage IV were most common in the spring (November through February), whereas females with their egg mass exposed were most frequent from November through March. The reproductive period of U. cordatus in mangroves of the study region occurred from October to March. The reproductive events observed in the present study suggest that spermatophores acquired during copulation, which takes place during the ‘andada’, are only used in the reproductive period of the following year.     

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.     

The dynamics of oocyte growth during vitellogenesis in the rainbow trout (Oncorhynchus mykiss)

This report describes the dynamics of oocyte growth during vitellogenesis in a population of virgin female rainbow trout. Indices of ovarian development increased dramatically during the period of study: the gonadosomatic index (GSI) increased over 50-fold, reaching a peak of 20 just before ovulation; the mean oocyte diameter increased from less than 1 mm to 5.4 mm; and plasma levels of vitellogenin increased from less than 1.5 mg/ml to 25 mg/ml. There were no changes in the numbers of developing oocytes (measuring 0.5 mm or greater in diameter) from the time when the majority of oocytes undergoing secondary development had entered vitellogenesis in August to ovulation in February (averaging 4000 oocytes per fish). The increase in ovary weight during vitellogenesis was, therefore, due to an increase in the size of oocytes rather than to recruitment of more maturing oocytes. The numbers of vitellogenic oocytes in the ovary during the entire study also suggested that atresia of vitellogenic oocytes does not play a prominent role in determining fecundity. During early vitellogenesis, the volume of maturing oocytes within an ovary varied by as much as 250-fold. From September onwards, when all oocytes to be ovulated that season had entered vitellogenesis, a gradual uniformity in size began to develop, such that at ovulation, in February, all the eggs were very similar in size (there was less than a 2-fold variation in volume). The pattern of growth of oocytes in an ovary during vitellogenesis suggests that growth between oocytes is closely coordinated.     

Autonomous yolk protein synthesis in ovaries ofDrosophila cultured in vivo

Summary Immature ovaries ofDrosophila mercatorum were injected into young larvae and into adult males ofD. mercatorum, D. melanogaster, D. hydei, D. virilis, andZaprionius vittiger. These homo- and heteroplastic transplantations allow normal vitellogenesis to occur in the donor ovary. By SDS gel electrophoresis, we identified the major species-specific yolk proteins of mature eggs (stage 14) which were exclusively of donor-specific origin. Other experiments withD. hydei andZ. vittiger showed that, when females were used as hosts, the host-specific yolk proteins became incorporated into the donor eggs. When two immature ovaries, one ofD. mercatorum and one ofD. hydei, were co-cultured in males, again only the donor-specific yolk proteins were found in the mature eggs implying that these yolk proteins were not released into the host hemolymph.A parthenogenetic strain ofD. mercatorum was used to demonstrate the ability of transplanted immature ovaries to produce viable eggs which can give rise to fertile adults.The role of the species-specific yolk proteins is discussed with respect to the dual origin of these proteins during normal vitellogenesis, i.e., an autonomous synthesis within the ovary itself in addition to the well-known production by the fat body. Further experiments with pupae as hosts indicate that even in the absence of juvenile hormone and in the presence of high doses of ecdysone, vitellogenesis can proceed within the donor ovary.Based on these experiments, a new hyopthesis on the hormonal control of vitellogenesis inDrosophila is presented. We propose that yolk proteins derived from the fat body are controlled by juvenile hormone, whereas the independent and autonomous vitellogenesis within the ovary itself is controlled by endogenously synthesized ecdysone.     

Gonad history of the Antarctic krill Euphausia superba dana during its breeding season

Summary Krill were collected in January–February 1986, north of Prydz Bay, Antarctica. Their gonad history was reconstructed from observations of live krill maintained on board ship, and subsequently fixed for histology. Size, molt-stage and external stage of sexual maturity were recorded for each individual. Males appeared to be continually producing sperm. Among mature females, the ovaries had various compositional zones: germinal zones and 1 to 3 batches of maturing oocytes (in primary or secondary vitellogenesis) were simultaneously present. Therefore a female can successively lay at least three batches of eggs, at short intervals corresponding to the duration of one cycle of secondary vitellogenesis. Most post-spawn females had reverted to juvenile status (ovary reduced to germinal zones). Large females were found with an already reorganized ovary with numerous secondary oogonia and very young oocytes. It is concluded that oogenesis occurs before the winter rest and that only the vitellogenetic cycles are postponned until the next reproductive season.     

Ion current activity and molecules modulating maturation and growth stages of ascidian (Ciona intestinalis) oocytes

Electrophysiological techniques were used to study ion currents in the ascidian Ciona intestinalis oocyte plasma membranes during different stages of growth and meiosis. Three stages (A, B, C) of immature oocytes were discriminated in the ovary, with the germinal vesicle (GV) showing specific different features of growth and maturation. Stage A (pre‐vitellogenic) oocytes exhibited the highest L‐type Ca²⁺current activity, and were incompetent for meiosis resumption. Stage B (vitellogenic) oocytes showed Na⁺ currents that remained high during the maturation, up to the post‐vitellogenic stage C oocytes. The latter had acquired meiotic competence, undergoing spontaneous maturation and interacting with the spermatozoon. However, fertilized oocytes did not produce normal larvae, suggesting that cytoplasmic maturation plays a specific role in embryo development. Spontaneous maturation was inhibited at low pH whereas trypsin was able to trigger germinal vesicle breakdown (GVBD) regardless of pH; in addition spontaneous maturation was not affected by removal of follicle cells or by inhibiting junctional communication between oocyte and follicle cells. Taken together these results imply: (i) Ca²⁺ and Na⁺ currents are involved in meiotic progression, growth, and acquisition of meiotic competence; (ii) trypsin‐like molecules may have a role as candidates for providing the physiological stimulus to resume meiosis. Finally, we provide evidence that follicle cells in Ciona are not involved in triggering GVBD as it occurs in other ascidians. Mol. Reprod. Dev. 76: 1084–1093, 2009. © 2009 Wiley‐Liss, Inc.     

Anatomy and ultrastructure of the female reproductive system of Pleioplana atomata (Platyhelminthes: Polycladida)

The ultrastructure of the female reproductive system of the polyclad flatworm Pleioplana atomata is described. Numerous ovaries are scattered throughout the entire body but are mainly concentrated on the dorsal side. Within an ovary, a germinative zone with oogonia and prefolicular cells is located in the dorsal part of the ovary. The remaining part of the gonad is filled with previtellogenic and early vitellogenic oocytes enwrapped by follicular cells. During previtellogenesis, oocytes produce numerous eggshell globules, which are distributed into the cortical area of the cell in later stages. Eventually, these globules release their contents into the space between the eggshell cover and oolemma. Similar types of globules are also found in others flatworms, and may represent useful phylogenetic characters. Entolecital, vitellogenic oocytes pass to paired uteri, where vitellogenesis is completed. The remainder of the female reproductive system consists of paired thin uterine ducts that join a vagina. The distal part of the long, curved vagina forms a large Lang's vesicle, while the proximal part is connected to a female atrium leading to a female gonopore. We hypothesize that Lang's vesicle functions in the digestion of excess sperm received. Two kinds of different shell (cement) glands that release their secretion into the vagina are identified. Both are unicellular glands and each gland cell connects to the lumen of the vagina via an individual canal. Similar glands in other acotylean polyclads have been implicated in the formation of eggshell covers. J. Morphol. 2009. © 2008 Wiley‐Liss, Inc.     

Histological classification of oocyte growth and the dynamics of ovarian recrudescence in Tilapia zillii

Serum levels of 17β-oestradiol and testosterone peaked and fell within 6 days of spawning in Tilapia zillii suggesting that vitellogenic growth began as early as day 2 or 3 postspawning. As early as day 8, stage 6/7 (late nitellogenic and maturing) oocytes occupied 60–70% of the ovary. From day 8 onwards the proportion of stage 6/7 oocytes changed little, though I _G increased (as oocytes grew) to reach maximal levels of ∼ 5·5% by day 14. I _G was correlated significantly to the proportion of stage 6/7 oocytes. Postovulatory follicles were observed immediately following spawning occupying up to ∼ 7% of the ovary but were not present from day 3 onwards. Atretic oocytes were found throughout the time period monitored (generally occupying <2% of the ovary) but were more prevalent from day 18 onwards. Data suggest that previtellogenic oocytes are recruited into vitellogenic growth immediately after spawning and can complete vitellogenesis as early as day 8 postspawning. Knowledge of this timing is likely to be important in the development of spawning induction programmes in T. zillii and other related species.     

Insulin signaling is necessary for vitellogenesis in Drosophila melanogaster independent of the roles of juvenile hormone and ecdysteroids: female sterility of the chico1 insulin signaling mutation is autonomous to the ovary

It has been suggested that insulin signaling mutations of Drosophila melanogaster are sterile and long-lived because of juvenile hormone (JH) and ecdysteroid deficiency. However, female sterility of an insulin/IGF-like signaling mutant (chico(1)) of D. melanogaster is not mediated by downstream systemic signaling in terms of major alterations in JH or ecdysteroid levels. chico(1) is a null mutation in the insulin substrate protein (CHICO) gene of D. melanogaster. Homozygous chico(1) females are sterile and their oocytes do not mature beyond the last previtellogenic stage. Homozygous chico(1) females exhibit approximately wild-type rates of JH biosynthesis, ovarian release of ecdysteroids and haemolymph ecdysteroid levels, suggesting that these two major hormone systems play no role in producing the sterility. Previtellogenic wild-type ovaries transplanted into homozygous chico(1) females underwent vitellogenesis, showing that systemic factors present in mutant females are sufficient to support normal vitellogenesis. chico(1) ovaries transplanted into wild-type females did not undergo vitellogenesis indicating that CHICO is necessary in the ovary for vitellogenic maturation. The ovary transplant experiments corroborate the endocrine results and demonstrate that insulin/insulin-like signaling (IIS) is necessary for vitellogenesis even when sufficient levels of JH, ecdysteroids or other factors are present.