Does ovarian ecdysone stimulate mosquitoes to synthesize vitellogenin?

Physiological amounts of 20-hydroxyecdysone do not initiate vitellogenin synthesis in unfed, non-vitellogenic mosquitoes. Injecting more than 10,000 times the physiological amount induced synthesis, but considerably less than was induced by a blood meal. A dose of 20-hydroxyecdysone which exceeded the physiological level only several hundred times, did not sustain vitellogenin synthesis, when blood-fed mosquitoes were ovariectomized just prior to injection. Transplanting ovaries from vitellogenic to non-vitellogenic females did not initiate synthesis of vitellogenin in the recipient. In vitro, neither 20-hydroxyecdysone nor the ovaries of vitellogenic females were able to induce synthesis of vitellogenin in non-vitellogenic fat bodies. These experiments suggest that ecdysteroid, released by the ovaries, does not initiate ovarian development in mosquitoes.     

The relationship between nutrition,vitellogenin, vitellin and ovarian development in the housefly, Musca domestica L.

The effect of adult nutrition on oögenesis during the first gonotropic cycle was studied in three strains of the housefly, Musca domestica. Two of the strains were anautogenous and the third was autogenous. In these strains, three subunits (51, 43 and 42 kdaltons) of vitellogenin and vitellin were electrophoretically identical using SDS-PAGE electrophoresis for haemolymph proteins of vitellogenic females and for egg extracts. Each developmental stage of the ovary in individual females flies of both autogenous and anautogenous strains fed on either sugar or protein clearly reflected the appearance of electrophoretic bands for vitellogenin and vitellin. Using immunological analysis, a very small amount of vitellogenin was detectable in the haemolymph of previtellogenic flies. The highest level of vitellogenin appeared in the haemolymph at the middle of vitellogenic phase and reached about 25% of the total haemolymph protein. There were differences in vitellogenin concentration in females with mature eggs between the two anautogenous strains: vitellogenin was not detectable in one strain, and the other showed 30% of the maximal level.     

Vitellogenin titre in haemolymph of Locusta migratoria in normal adults,after ovariectomy,and in response to methoprene

Vitellogenin in the haemolymph of Locusta migratoria was assayed by rocket immunoelectrophoresis to elucidate aspects of its regulation. In many normal adult females, vitellogenin first appeared on days 5–9, rose quickly to peak levels, and declined before a second vitellogenic cycle; in others, it appeared later and built up more slowly. The timing of first appearance of vitellogenin, and proportions of early and late-developing individuals, differed markedly in groups from the same colony assayed in different years, suggesting effects of both genetic and environmental variation. Average peak levels of vitellogenin were 25–30 mg/ml. After ovariectomy, vitellogenin appeared near the normal time and increased for several weeks to about 300 mg/ml; haemolymph volume also increased greatly, so that the total haemolymph-vitellogenin pool reached about 300 mg/individual, or 100 times the normal amount. After ovariectomy, no cyclicity of vitellogenin accumulation was apparent. These results show that the ovary is not required for stimulation of vitellogenin synthesis, and suggest that normal cycling may depend on inhibition by the mature ovary. Females treated with ethoxyprecocene on day 1 of adult life to inactivate the corpora allata did not produce vitellogenin, but were induced to do so with the juvenile hormone analogue, methoprene. After injection of 150 μg of methoprene in mineral oil, there was one day lag, then vitellogenin increased in the haemolymph to the normal peak level and declined slowly to zero during 5 weeks; after a second injection of methoprene, vitellogenin re-appeared more rapidly, with less lag, reflecting accelerated secondary hormonal stimulation of vitellogenin synthesis in the fat body. Adult males showed no detectable haemolymph vitellogenin even after injection of large doses of methoprene.     

Vitellogenin and vitellin from the blowfly Calliphora vicina: Occurrence,purification and antigenic characterization

The occurrence and purification of vitellogenin and vitellin from Calliphora vicina Rob.-Dev. (= C. erythrocephala (Meig.)) are described together with the preparation of specific anti-vitellogenin antibodies. C. vicina vitellogenin and vitellin were purified from ovaries and eggs respectively; both proteins contain two polypeptide subunits identical to the dominating polypeptides in the growing oocytes. The polypeptides show molecular weights of 52,000 and 48,500 respectively, and are associated with carbohydrate and lipid. Polypeptides of similar size could be identified in haemolymph from yolk-depositing females, but were absent in ovariectomized females. The anti-bodies specifically precipitated the vitellogenin polypeptides from fat body homogenates of females depositing yolk or from the purified vitellogenin. Therefore, these antibodies were judged suitable for use in a study on the ultrastructural localization of vitellogenin in fat body cells (Thomsenet al., 1980).     

Subcellular localization of vitellogenin in crustacean adipocytes by the unlabelled antibody enzyme method

The subepidermal fat body of the Amphipod Crustacean Orchestia gammarellus shows ultrastructural modifications related to vitellogenin synthesis. In the adipocytes of vitellogenic females, the rough endoplasmic reticulum is well developed whereas in those of males and non-vitellogenic females it is almost entirely absent; lipids and glycogen are, on the contrary, less abundant. The unlabelled antibody enzyme method shows the presence of vitellogenin in the dense bodies of the adipocytes of vitellogenic females. Adipocytes of males and non-vitellogenic females are not immunoreactive.     

An electrophoretic study of proteins of the ovary,fat body,and haemolymph in the migratory grasshopper, Melanoplus sanguinipes

Electrophoretic separation of saline extracts from the ovary revealed 14 proteins. Twelve proteins were detected in the fat body, of which seven had electrophoretic mobilities identical to those in the ovary. Similarly, eight of 16 proteins in the haemolymph of vitellogenic females ahad electrophoretically identical counterparts in the ovary. As these proteins accumulate in the haemolymph of ovariectomized females, the findings suggest that most yolk proteins are synthesized in the fat body. Although most female haemolymph proteins are present in males, two of the predominant yolk protiens are absent and represent female-specific proteins.Although certain proteins accumulate in the haemolymph of allatectomized females, the major ovarian proteins are absent or present in low concentrations. However, 48 hr after allatectomized females are treated with a juvenile hormone analogue, the haemolymph protein pattern resembles that of a normal female. This suggests that the corpora allata stimulate the synthesis of female-specific and other vitellogenic proteins. The median neurosecretory cells (mNSC) are also necessary for synthesis of female-specific proteins. Furthermore, proteins which are present in allatectomized females are absent in mNSC-cauterized insects suggesting that the mNSC stimulate general protein synthesis.     

EFFECT OF ECDYSTERONE ON VITELLOGENIN CONCENTRATION IN HAEMOLYMPH OF MALE AND FEMALE SARCOPHAGA BULLATA

Using Polyacrylamide gel electrophoresis, cycloheximide, incorporation of ³H-labelled amino acids and immunological methods, we have demonstrated that injection of ecdy- sterone induces de novo synthesis and release of vitellogenin in both sexes of Sarcophaga bullata. Vitellogenin concentrations were measured by the Mancini-radial immunodiffusion technique. In males a dose as low as 1 ng always makes vitellogenin appear in the haemolymph but very reproducible results are only obtained when doses varying from 10 to 250 ng were injected. In this range, the dose-response curve was linear on a semi- logarithmic scale.

In females, vitellogenin concentration remained low until a few hours after liver feeding and thereafter it rose sharply and reached its maximum about 24 h after the protein meal. 100 μg 6-hydroxydopamine HCl, injected before liver feeding in 4-day-old females, inhibited vitellogenin synthesis and yolk deposition, probably by interfering with the release of a brain hormone. This inhibitory effect on vitellogenin synthesis, but not that on yolk deposition, could be overruled by injection of ecdysterone. Juvenile hormone was ineffective on both. Females, ovariectomized on day 2 or 3, accumulated vitellogenin in their haemolymph, indicating that the continuous presence of the ovaries was not required for vitellogenin synthesis. The possible relation between the gonadotrophs hormone from the brain, vitellogenin synthesis and moulting hormone metabolism is discussed.     

Vitellogenin synthesis in blood-fed Aedes aegypti in the absence of the head,thorax and ovaries

A blood meal initiates oöcyte maturation in Aedes aegypti, and we have used rocket immunoelectrophoresis to investigate the function of midgut, ovaries, and head in the onset of vitellogenin synthesis. Non-blood-fed females and those fed blood (by enema) containing soybean trypsin inhibitor never contained vitellogenin. This demonstrates that the pressure of an undigested blood meal on stretch receptors of the midgut plays no role in the induction of vitellogenin synthesis, rather the stimulus is a digestion product of blood.When females were ovariectomized or decapitated and then fed blood, the haemolymph contained newly synthesized vitellogenin 24 h later. This was also demonstrated in isolated ovariectomized abdomens. Apparently, induction of vitellogenin synthesis does not require factors from either the head, thorax, or ovaries. When ovariectomy or decapitation was postponed after a blood meal, the level of vitellogenin in the haemolymph rose. Therefore, interaction of factors from the head and ovaries maintain the synthesis needed for oöcyte maturation.     

On the relative importance of juvenile hormone and vitellogenin for oöcyte growth in the cockroach Nauphoeta cinerea

The corpora allata of castrated females of Nauphoeta grow only very slightly and do not reach a volume greater than that of the glands of normal females during gestation. These small corpora allata are, however, active and are responsible for the synthesis of vitellogenin (female specific protein) in large amounts. Besides vitellogenin the other haemolymph proteins are also synthesized and accumulated in the haemolymph in much higher concentrations than in normal females. Implanted oöcytes grow in castrated as well as in normal females at about the same rate until the tenth day of the oöcyte maturation period. Thereafter they only grow in castrated females. If castrated and normal females are decapitated, their protein content decreases. At the same time the growth stimulating capacity of their haemolymph decreases at a much faster rate. If oöcytes are implanted in castrated and decapitated females after 4 days they cannot grow any more although the vitellogenin titre of the haemolymph is still much higher than it is at any time in normal females. It can be concluded that vitellogenin alone cannot induce oöcyte growth and that juvenile hormone is necessary as well for vitellogenin synthesis as for its incorporation into the oöcytes. However, in insects rich in vitellogenin juvenile hormone leads to a more rapid oöcyte growth than in insects containing only small amounts of this protein.     

Vitellogenin fluctuations in haemolymph and fat body and dynamics of uptake into oöcytes during the reproductive cycle of Diploptera punctata

Haemolymph and fat body soluble protein titres have been examined during the reproductive cycle of Diploptera punctata, with particular emphasis on the occurrence of vitellogenin and its uptake into the developing oöcytes. Vitellogenin was first detected in the haemolymph of mated females 2 days after adult eclosion at about the same time that vitellin deposition in basal oöcytes began. Peak haemolymph titres of vitellogenin occurred on day 6, correlated with the completion of yolk uptake. Thereafter vitellogenin levels declined and were generally undetectable throughout most of gestation, rising again shortly before parturition in association with the second gonotrophic cycle. Total haemolymph protein levels were not correlated with vitellogenesis.Soluble fat body vitellogenin titres of mated females remained low during the first oöcyte growth period but then rose several-fold at its completion and remained high throughout pregnancy and the second gonotrophic cycle. Total fat body soluble proteins decline after adult eclosion in association with oöcyte growth.Vitellin accumulation in basal oöcytes was related linearly to increase in volume until the onset of chorion formation. Thus no post-vitellogenic growth period was detected.     

Vitellins and vitellogenins of Dysdercus koenigii (Heteroptera: Pyrrhocoridae)--identification, purification and temporal pattern

Two vitellins, VtA and VtB, were purified from the eggs of Dysdercus koenigii by gel filtration and ion exchange chromatography. VtA and VtB have molecular weights of 290 and 260 kDa, respectively. Both Vts are glycolipoproteinaceous in nature. VtA is composed of three polypeptides of M(r) 116, 92 and 62 kDa while VtB contained an additional subunit of M(r) 40 kDa. All subunits except the 116-kDa subunit are glycolipopolypeptides. Polyclonal antibody raised against VtA (anti-VtA antibody) cross-reacted with VtB and also with vitellogenic haemolymph and ovaries and pre-vitellogenic fat bodies, but not with haemolymph from either adult male, fifth instar female, or pre-vitellogenic females demonstrating sex and stage specificity of the Vts. Immunoblots in the presence of anti-VtA revealed two proteins (of 290 and 260 kDa) in both vitellogenic haemolymph and pre-vitellogenic fat bodies that are recognised as D. koenigii Vgs. In newly emerged females, Vgs appeared on day 1 in fat bodies and on day 3 in haemolymph and ovaries. Vg concentration was maximum on day 2 in fat body, day 4 in haemolymph and day 7 in ovary. Although the biochemical and temporal characteristics of these proteins show similarity to some hemipterans, they are strikingly dissimilar with those of a very closely related species.     

The neuro-endocrine control of protein metabolism in the migratory grasshopper, Melanoplus sanguinipes

In normal females, distinct fluctuations in the protein content of the fat body and haemolymph are evident during each gonotrophic period. These fluctuations partly reflect changes in the protein requirements of the developing oocytes. Almost one half of the total protein deposited in the mature ovary is sequestered during the final stages of vitellogenesis when protein accumulated in the fat body and haemolymph is rapidly depleted. Although similar amounts of protein are deposited in the ovary during the first and subsequent gonotrophic periods, significantly less extraovarian protein is present throughout the latter periods.The accumulation of large amounts of protein in the fat body and haemolymph of ovariectomized females suggests that most yolk protein is of extraovarian origin. As the total protein content of these insects is comparable to that of vitellogenic females, ovariectomy apparently has no immediate effect on protein synthesis.Allatectomy or cautery of the median neurosecretory cells (mNSC) prevents vitellogenesis. Although protein gradually accumulates in the fat body and haemolymph of allatectomized females, the total protein content of these insects is significantly lower than that of controls. Treatment of allatectomized females with juvenile hormone analogue leads to a temporary but significant increase in the protein content of the fat body. However, the subsequent decline in fat body protein is paralleled by a pronounced increase in the protein content of the ovary. These findings suggest that the corpora allata (CA) stimulate both yolk protein synthesis in the fat body and its uptake into the ovary. The total protein content of mNSC-cauterized females is less than that of allatectomized females. This observation supports the proposal that the mNSC have not only an allatotropic effect but also a direct effect on protein synthesis.     

Protein synthesis and secretion by the locust fat body after ovariectomy

The synthesis and secretion of proteins, including vitellogenin, by the locust fat body were investigated in vivo and in vitro at various times after ovariectomy. The rate of overall protein synthesis and secretion by the fat body in vivo is significantly less in ovariectomized animals than in the controls two to three weeks after the operation, the difference in the rates of secretion of vitellin antibody-precipitable protein being even more pronounced and detectable earlier. The significantly greater amount of newly synthesized vitellogenin retained in the fat body of ovariectomized animals is insufficient to account for this difference. The secretion of newly synthesized protein by the fat bodies of ovariectomized locusts in vitro is significantly less than that of control fat bodies, the difference being particularly marked in the case of vitellogenin. The polysome populations of fat bodies of ovariectomized and control females are quantitatively similar and the amounts of total protein and vitellin antibody-precipitable protein synthesized by these polysomes in a cell-free system do not differ significantly.     

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.     

The roles of juvenile hormone and 20-hydroxy-ecdysone during vitellogenesis in isolated abdomens of Drosophila melanogaster

Both juvenile hormone and 20-hydroxy-ecdysone seem to be involved in the regulation of vitellogenesis in Drosophila melanogaster. It is the purpose of this paper to begin to define the functions of these two hormones. Although vitellogenin synthesis does not occur at a high rate in 1-day-old female abdomens isolated from the head and thorax before 0.75 hr after eclosion, both ZR515 (a juvenile hormone analogue) and 20-hydroxy-ecdysone can cause in these preparations vitellogenin synthesis and secretion into the haemolymph. The synthesis and secretion into the haemolymph of all three vitellogenins which are detectable by electrophoresis in sodium dodecyl sulphate-containing gels of polyacrylamide is promoted by both hormones. That result excludes the hypothesis that these two hormones regulate the synthesis of different vitellogenins. A dose-response curve showed that an injection of 0.2 μl of a 10^?6 M 20-hydroxy-ecdysone solution was sufficient to promote vitellogenin synthesis and secretion in isolated abdomens. Ovaries from isolated female abdomens treated with juvenile hormone analogue showed nearly normal amounts of all three vitellogenins and morphologically normal advanced vitellogenic follicles, whereas ovaries from isolated abdomens treated with 20-hydroxy-ecdysone contained little vitellogenin and no vitellogenic follicles. We conclude that under the conditions used, juvenile hormone permits vitellogenin uptake into the oöcyte much more readily than does 20-hydroxy-ecdysone.     

Undegraded vitellogenin polysomes from female insect fat bodies

Fat body cells of vitellogenic females of the cockroach $\text{Leucophaea maderae}$ contain a prominent population of large polysomes of approximately 35–40 ribosomes whereas fat bodies of non-vitellogenic females or males of any age do not have these polysomes. Anti-vitellogenin recognizes newly synthesized nascent vitellogenin associated with these large polysomes. Adenosine labelled RNA is likewise precipitated by anti-vitellogenin primarily in the region of this class of polysomes. It is concluded that the class of large polysomes represents the vitellogenin polysomes.     

Juvenile hormone-dependent vitellogenin synthesis in Locusta migratoria fat body: Inducibility related to sex and stage

Juvenile hormone (JH)-dependent vitellogenin (Vg) synthesis in the fat body of Locusta migratoria is normally limited to sexually mature adult females. As a step toward examining the basis of this limitation, we have tested female and male locusts in a series of stages after the third larval molt for inducibility of Vg synthesis by the synthetic JH analog, methoprene. We find that in the fourth and fifth larval instars fat body of both sexes can be induced to produce Vg, but in the adult stage females respond strongly while no more than trace amounts can be induced in males. Quantitative assays show relative responsiveness in the order: adult female > fifth instar female > fifth instar male ? adult male. During the fifth instar of both sexes, maximal vitellogenic response was obtained in midinstar. After the larval-adult ecdysis, female fat body was unresponsive during the first 4 days, then responsiveness increased and by Day 8 after ecdysis fat bodies were fully as competent to produce Vg as at Day 14, the usual maximum of the first vitellogenic cycle due to endogenous JH. Larval and adult female fat bodies implanted into male larvae are competent for Vg synthesis after metamorphosis, so that the differences between adult male and female cannot be imposed by the male milieu intérieur during the larval-adult molt. In male and female precocious adults, produced by treatment of fourth instars with precocene, fat body responded to methoprene as in normal adults. We conclude that factors intrinsic to the fat body cells, determined early in development, are responsible for differential gene programing in males and females, which is partially expressed by the fifth instar but fully manifest only after a molt in the absence of JH.     

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.     

Release of egg development neurosecretory hormone in Aedes aegypti and Aedes taeniorhynchus induced by an ovarian factor

Ovariectomized Aedes aegypti do not synthesize vitellogenin after a blood meal, unless an ovary from a blood-fed donor is implanted. Decapitation, however, prior to implantation inhibits vitellogenin synthesis. A female ovariectomized and decapitated 6 hr after a blood meal, synthesizes vitellogenin if an ovary from a blood-fed donor is implanted. On the other hand, females that are fed on blood and immediately decapitated can not be stimulated to synthesize vitellogenin with implanted ovaries removed from blood-fed donors. These experiments led to the hypothesis that the blood meal stimulates the ovary to secrete a corpus cardiacum stimulating factor, that in turn promotes release of egg development neurosecretory hormone stored in the corpus cardiacum.Injection of 20-hydroxy-ecdysone or ovarian extract prepared from ovaries removed from unfed females does not release egg development neurosecretory hormone. Thus corpus cardiacum stimulating factor is not 20-hydroxy-ecdysone, and ovaries removed from unfed females do not store it.The rate of inactivation of egg development neurosecretory hormone released from the corpus cardiacum after a blood meal was investigated by implanting an ovary into females that were blood fed for various intervals than decapitated and ovariectomized. Seventy per cent of implants grow when the operation is done 18 hr after feeding, and 30% when the operation is done between 18 and 24 hr after feeding, indicating that egg development neurosecretory hormone is stable for the first 18 hr after a blood meal.Aedes taeniorhynchus females ovariectomized 24 hr after adult emergence do not synthesize vitellogenin. When such a female is implanted with an ovary removed from a sugar-fed or blood-fed Aedes aegypti donor vitellogenin synthesis is initiated, and the implant grows. Decapitation prior to implantation inhibit vitellogenin synthesis and implants do not grow. These results indicate that corpus cardiacum stimulating factor is not species specific.     

Haemolymph vitellogenin,juvenile hormone,and oöcyte growth in the adult cockroach Nauphoeta cinerea during first pre-oviposition period

In the cockroach Nauphoeta cinerea the incorporation of a protein of low solubility into the oöcytes begins at day 5 of its adult life. An immunologically identical protein appears in the haemolymph two days earlier. The concentration of this protein, i.e. ‘vitellogenin’ in the haemolymph increases up to the onset of yolk incorporation into the oöcytes. During ovarian development no correlation could be detected between vitellogenin titre and several other parameters (ovary dry weight, length of the basal oöcytes, haemolymph protein concentration, body weight and age when ovulation occurred). In young females vitellogenin titre depends on the age, i.e. the volume of the corpora allata and hence on the presence and the titre of JH. During the period of egg maturation the total haemolymph protein concentration generally tends to drop while materials not precipitable by trichloracetic acid circulate at higher concentration after ecdysis and before ovulation.Early decapitation prevents vitellogenin synthesis and oöcyte growth, but when JH is applied to decapitated females, the normal vitellogenin titre is re-established, ovarian development, however, cannot be fully resumed. A dose-response curve shows that serial application of the hormone is much more effective than single large doses. Farnesylmethylester, a JH mimic, is about a hundred times less active, but more persistent than JH. Copulation seems to enhance the synthesis and release of endogenous JH, while food and water uptake are necessary to guarantee and optimal ovarian development. JH and high vitellogenin titre never restore ovarian development in females deprived of food and/or water or in those decapitated shortly after ecdysis.