Ecdysteroid levels during ovarian development and embryogenesis in the spider crab Acanthonyx lunulatus

Function Analysis of Cholesterol 7-Desaturase in Ovarian Maturation and Molting in Macrobrachium nipponense: Providing Evidence for Reproductive Molting Progress

The Cholesterol 7-desaturase gene plays an important role in insect ecdysone synthesis, but its role in ovarian development has not been reported. In this study, characteristics and the phylogenetic relationship of Cholesterol 7-desaturase were identified by bioinformatics. qPCR showed that the Mn-CH7D gene was highly expressed in the ovary, which was much higher than that in other tissues, and the expression level of Mn-CH7D reached the highest level at the third stage of the ovarian development stage (O-III). During embryonic development, the Mn-CH7D gene expression was highest in the zoea stage. The function of the Mn-CH7D gene was explored by RNA interference. The experimental group was injected with Mn-CH7D dsRNA through the pericardial cavity of M. nipponense, while the control group was injected with the same volume of dsGFP. Statistical analysis of gonadal development and GSI calculation showed that the silencing of Mn-CH7D resulted in the suppression of gonadal development. In addition, the molting frequency of the experimental group was significantly lower than that of the control group during the second molting cycle after silencing Mn-CH7D. On the seventh day after silencing, ecdysone content in the experimental group was significantly reduced. These results demonstrated that the Mn-CH7D gene played a dual role in ovarian maturation and molting of M. nipponense.

Functional expression patterns of four ecdysteroid receptor isoforms indicate their different functions during vitellogenesis of Chinese mitten crab, Eriocheir sinensis

In arthropods, alternative splicing of ecdysteroid receptor gene (EcR) leads to multiple functions of different EcR isoforms during metamorphosis, growth and ovarian development via ecdysteroid signaling pathway. This study was conducted to investigate the expression patterns of four EcRs of Eriocheir sinensis (EsEcRs) and the changes of haemolymph ecdysteroid titer during the ovarian development. The results showed that four EsEcR isoforms had the tissue-specific expression among 12 examined tissues, and the highest transcript levels of the four EsEcR isoforms were detected in Y-organ or sinus gland. During the ovarian development, EsEcR1 showed the highest transcript abundance of the four EsEcR isoforms. The expression profiles of all the EsEcR isoforms were similar in the hepatopancreas during the ovarian maturation cycle of E. sinensis with a trend of "high-low-high-low". In ovary, the highest expression levels of EsEcR1 and EsEcR4 were both found at stage V ovary, while the peaks of EsEcR2 and EsEcR3 were found on stage III ovary and stage IV ovary, respectively. Meanwhile, the ecdysteroid titer in haemolymph decreased gradually during ovarian maturation cycle. Further regression analysis revealed significant negative correlations were found between the ovarian EsEcR3/ EsEcR4 expression levels and haemolymph ecdysteroid titer during part or whole ovarian development cycle. These results together indicated that four EsEcR isoforms may have different functions during ovary maturation of E. sinensis. All EcR isoforms and ecdysteroid seemed to have important roles in the hepatopancreas during early ovarian development stages, while EsEcR3 and EsEcR4 were closely related to the mid-late vitellogenesis stages.

Changes in ecdysteroid levels and expression patterns of ecdysteroid-responsive factors and neuropeptide hormones during the embryogenesis of the blue crab, Callinectes sapidus

Embryogenesis requires the involvement and coordination of multiple networks of various genes, according to a timeline governing development. Crustacean embryogenesis usually includes the first molt, a process that is known to be positively controlled by ecdysteroids. We determined the amounts of ecdysteroids, as well as other related factors: the ecdysone receptor (CasEcR), the retinoid X receptor (CasRXR), the molt-inhibiting hormone (CasMIH), and crustacean hyperglycemic hormone (CasCHH) during the ovarian and embryonic developments of Callinectes sapidus. In summary, the ovaries at stages 1-4 have expression levels of maternal CasEcR and CasRXR 10-50 times higher than levels seen in embryos at the yolk stage. This large difference in the amount of the these factors in C. sapidus ovaries suggests that these maternal ecdysteroid-responsive factors may be utilized at the initiation of embryogenesis. During embryogenesis, the changes in total ecdysteroids and levels of CasEcR and CasRXR expression are similar to those observed in juvenile molts. The full-length cDNA sequence of the C. sapidus BTB domain protein (CasBTBDP) initially isolated from Y-organ cDNA, contains only Broad-Complex, Tramtrack, and Bric a brac (BTB) domains. The levels of CasBTBDP are kept constant throughout embryogenesis. The expression profiles of CasMIH and CasCHH are similar to the titers of ecdysteroids. However, the timing of their appearance is followed by increases in CasEcRs and CasRXRs, implying that the expressions of these neuropeptides may be influenced by ecdysteroids. Moreover, the ecdysteroid profile during embryogenesis may track directly with the timing of organogenesis of Y-organs and their activity. Our work reports, for first time, the observed expression and changes of ecdysteroid-responsive factors, along with CasCHH and CasMIH, during embryogenesis in the crustacean C. sapidus.

Reproductive regulators in decapod crustaceans: an overview

Control of reproductive development in crustaceans requires neuropeptides, ecdysone and methyl farnesoate (MF). A major source of neuropeptides is the X-organ-sinus gland (XO-SG) complex located in the eyestalk ganglia of crustaceans. The other regulatory factors (either peptides or neuromodulators) are produced in the brain and thoracic ganglia (TG). Two other regulatory non-peptide compounds, the steroid ecdysone and the sesquiterpene MF, are produced by the Y-organs and the mandibular organs, respectively. In the current review, I have tried to recapitulate recent studies on the role of gonadal regulatory factors in regulating crustacean reproduction.

The effects of farnesoic acid and 20-hydroxyecdysone on vitellogenin gene expression in the lobster, Homarus americanus, and possible roles in the reproductive process

Reproduction in female lobster (Homarus americanus) is characterized by the maturation of the ovary, with a gradual increase in its size as a result of uptake of yolk protein precursor, vitellogenin (Vg) to the final product vitellin (Vn). Vn is formed by aggregation of several Vg subunits. In most decapods, the hepatopancreas is the major site of vitellogenin biosynthesis. The production of vitellogenin is controlled by endocrine factors. In this study, the effect of farnesoic acid (FA) and 20-hydroxyecdysone (20E) on production of vitellogenin by hepatopancreas (HaVg1) was investigated by in vitro organ explant HaVg1 gene expression was stimulated by FA or 20E in a dose-dependent manner. A 2-fold and 2.2-fold increase in HaVg1 gene expression was observed with 4.2 microM FA and 0.7 microM 20E, respectively. The stimulatory effect by either FA or 20E was observed principally during the first 90 min. Stimulation of HaVg1 gene expression by FA and 20E together is greater (3.3-fold increase) than that of either hormone alone. This stimulation was also observed within the first 90 min. To study the synergistic effect of these two hormones, FA and 20E were tested separately and together at low concentration (42.3 nM and 6.7 nM, respectively). Combined use of FA and 20E increased HaVg1 gene expression synergistically, but not additively. These findings should contribute to our understanding of lobster reproduction and provide insights into manipulation of lobster reproduction in aquaculture or under captive conditions.

Ecdysteroid levels in Daphnia magna during a molt cycle: determination by radioimmunoassay (RIA) and liquid chromatography-mass spectrometry (LC-MS)

Despite their abundance and their enormous significance for various ecological processes, endocrine systems of microcrustaceans have been poorly investigated. Here, we used a highly sensitive radioimmunoassay (RIA) to determine free and conjugated ecdysteroid levels in whole-body extracts of adult Daphnia magna during a complete molt cycle. Ecdysteroid levels were predominated by free ecdysteroids. Starting from basal levels in the postmolt stage the concentration of free ecdysteroids increased sharply in the early premolt stage, followed by a sharp decline back to basal levels just prior to ecdysis. Polar and apolar ecdysteroid conjugates were found in rather low amounts with little variation during the molt cycle. Only small amounts of ecdysteroids were found in newly deposited eggs of D. magna, which suggest a sparing investment of maternal ecdysteroids into the eggs for early embryogenesis. As in whole-body extracts, free ecdysteroids were the predominant ecdysteroids found in eggs of D. magna, together with small amounts of polar and intermediary amounts of apolar conjugates. Hence, the pathways leading to polar and apolar ecdysteroid conjugates appear to be of minor importance in D. magna. Analyses of the immunodetectable peak in free ecdysteroids by liquid chromatography-mass spectrometry (LC-MS) revealed that molting is induced most probably by an increased level of 20-hydroxyecdysone. Microcrustaceans of the genus Daphnia are key components in freshwater food webs. Examination of the functional role of ecdysteroids in controlling developmental processes might help to understand the performance of the herbivorous grazer in its environment, in particular with regard to the adverse effects of environmental xenobiotics acting as endocrine disrupters.

Steroids in aquatic invertebrates

Steroid molecules are present in all invertebrates, and some of them have established hormonal roles: this is the case for ecdysteroids in arthropods and, to a lesser extent, for vertebrate-type steroids in molluscs. Steroids are not only hormones, they may also fulfill many other functions in chemical communication, chemical defense or even digestive physiology. The increasing occurrence of endocrine disruption problems caused by environmental pollutants, which interfere in particular with reproductive physiology of vertebrates but also of invertebrates has made necessary to better understand the endocrine physiology of the latter and the role of steroids in these processes. So many attempts are being made to better understand the endocrine roles of steroids in arthropods and molluscs, and to establish whether they also fulfill similar functions in other invertebrate phyla. At the moment, both the precise identification of these steroids, the determination of their origin (endogenous versus exogenous) and of their mechanism of action are under active investigation. This research takes profit of the development of genome sequencing programs on many invertebrate species, which allow the identification of receptors and/or biosynthetic enzymes, when related to their vertebrate counterparts, but the story is not so simple, as will be exemplified by estrogen receptors of molluscs.

Hormonal coordination of molting and female reproduction by ecdysteroids in the mole crab Emerita asiatica (Milne Edwards)

The measurement of hemolymph ecdysteroids using radioimmunoassay (RIA) indicates a biphasic increase during intermolt and premolt stages of the mole crab Emerita asiatica. The gradual rise during intermolt stage corresponds to vitellogenic activities in the ovary; whereas a distinctive premolt peak is characteristic of molting crustaceans. Injection experiments with 20-hydroxyecdysone (20E) during different molt cycle stages revealed the onset of precocious premolt changes, as determined by the epidermal retraction and setal development. Injection of 20E augmented protein synthesis in the ovary, hepatopancreas and integumentary tissues. Quantification of ecdysteroids in different developmental stages of ovary also indicated a progressive increase of ovarian ecdysteroids. Interestingly, the ovarian ecdysteroids after reaching a peak at C3 stage, start declining drastically to reach the lowest level at D(3-4) stage. This decline in the ovarian ecdysteroids is inversely related to rising hemolymph ecdysteroids during these active premolt stages. The hatching of the embryos, attached to the pleopods of the ovigerous females also occurs under a high titer of hemolymph ecdysteroids. In support, 20E injection at C3 stage crabs indicated a significant reduction in time duration of pleopodal embryonic development leading to hatching of zoea larvae. Understandably, the augmented hemolymph ecdysteroid titer helps in the synchronization of embryo hatching and the premolt changes, as occurring under the normal premolt conditions.

Comparative immunohistochemistry and cellular distribution of farnesoic acid O-methyltransferase in the shrimp and the crayfish

Farnesoic acid O-methyltransferase (FAMeT) catalyzes the conversion of farnesoic acid (FA) to methylfarnesoate (MF) by the mandibular organ (MO) of crustaceans. Here we report the cellular localization of FAMeT and radiochemical assay of endogenous FAMeT activity in shrimp (Metapenaeus ensis) and crayfish (Procambarus clarkii) tissues. As in the eyestalk (ES), FAMeT is concentrated in specific neurosecretory cells of the ventral nerve cord (VNC) whereas only weak FAMeT immunoreactivity was observed in the MO. FAMeT was also detected in the ventral nerve cord, heart (HET), eyestalk, and muscle of the juvenile shrimp. Although the VNC shows the greatest FAMeT immunoreactivity, the heart extract exhibited the highest FAMeT enzymatic activity. These results suggest that FAMeT in the VNC may be inactive or inactivated at the stages of development tested. Contrary to the previous reports in other crustaceans, MO extract in shrimp shows only low FAMeT activity. The eyestalk, epidermis, ovary and testis show appreciable FAMeT activity. The presence of FAMeT in neurosecretory cells of VNC and eyestalk of shrimp and crayfish implies a possible interaction of FAMeT with the eyestalk CHH-family of neuropeptides. The widespread activity of FAMeT suggests that it has a wide spectrum of action in many tissues that contribute to the function and regulation of MF synthesis in shrimp and crayfish.

Breeding biology of the intertidal sand crab, Emerita (Decapoda: Anomura)

Emerita is a burrowing mole crab or sand crab, adapted to life in wave-washed sandy beaches of temperate and tropical seas. The reproductive biology of this anomuran crab presents several peculiarities, all contributing to its adaptation to this harsh environmental niche. We discuss the following aspects: 1) sex ratio and size at sexual maturity, 2) neoteny and protandric hermaphroditism, 3) mating behaviour and sperm transfer strategy, 4) synchronisation of moulting and reproduction, 5) environmental impact on reproductive cycle and egg production, 6) biochemistry of yolk utilisation and energetics, 7) larval development, dispersal and settlement and 8) the value of Emerita as indicator species. These aspects are discussed in the light of the life history pattern, comprising a sedentary adult and pelagic larval phases. The successful colonisation of the physically challenging habitat of the sandy beach by Emerita is attributable largely to reproductive strategy and the larval developmental and recruitment pattern. Sensitivity to changing environmental conditions, including pollution, make this intertidal crab an indicator species for monitoring anthropogenic impact.

Function and cellular localization of farnesoic acid O-methyltransferase (FAMeT) in the shrimp, Metapenaeus ensis

The isoprenoid methyl farnesoate (MF) has been implicated in the regulation of crustacean development and reproduction in conjunction with eyestalk molt inhibiting hormones and ecdysteroids. Farnesoic acid O-methyltransferase (FAMeT) catalyzes the methylation of farnesoic acid (FA) to produce MF in the terminal step of MF synthesis. We have previously cloned and characterized the shrimp FAMeT. In the present study, recombinant FAMeT (rFAMeT) was produced for bioassay and antiserum generation. FAMeT is widely distributed in shrimp tissues with the highest concentration observed in the ventral nerve cord. Interestingly, an additional larger protein in the eyestalk also showed immunoreactivity to anti-FAMeT serum. FAMeT was localized in the neurosecretory cells of the X-organ-sinus gland complex of the eyestalk. As shown by RT-PCR, FAMeT mRNA is constitutively expressed throughout the molt cycle in the eyestalk and the ventral nerve cord. To show that our cloned gene product had FAMeT activity, we demonstrated that expressed rFAMeT gene product catalyzed the conversion of FA to MF in a radiochemical assay. The ubiquitous distribution of FAMeT suggests that this enzyme is involved in physiological processes in addition to gametogenesis, oocyte maturation and development and metamorphosis of the shrimp. We hypothesize that FAMeT directly or indirectly (through MF) modulates the reproduction and growth of crustaceans by interacting with the eyestalk neuropeptides as a consequence of its presence in the neurosecretory cells of the X-organ-sinus gland.

Clustering of mandibular organ-inhibiting hormone and moult-inhibiting hormone genes in the crab, Cancer pagurus, and implications for regulation of expression

Development and reproduction of crustaceans is regulated by a combination of neuropeptide hormones, ecdysteroids (moulting hormones) and the isoprenoid, methyl farnesoate (MF), the unepoxidised analogue of insect juvenile hormone-III (JH-III). MF and the ecdysteroids are respectively synthesised under the negative control of the sinus gland-derived mandibular organ-inhibiting hormones (MO-IHs) and moult-inhibiting hormone (MIH) that are produced in eyestalk neural ganglia. Previous work has demonstrated the existence of two isoforms of MO-IH, called MO-IH-1 and -2, that differ by a single amino acid in the mature peptide and one in the putative signal peptide. To study the structural organisation of the crab MIH and MO-IH genes, a genomic DNA library was constructed from DNA of an individual female crab and screened with both MO-IH and MIH probes. The results from genomic Southern blot analysis and library screening indicated that the Cancer pagurus genome contains at least two copies of the MIH gene and three copies of the MO-IH genes. Upon screening, two types of overlapping genomic clone were isolated. Each member of one type of genomic clone contains a single copy of each of the convergently transcribed MO-IH-1 and MIH genes clustered within 6.5kb. The other type contains only the MO-IH-2 gene, which is not closely linked to an MIH gene. There are three exons and two introns in all MIH and MO-IH genes analysed. The exon-intron boundary of the crab MIH and MO-IH genes follows Chambon's rule (GT-AG) for the splice donor and acceptor sites. The first intron occurs within the signal peptide region and the second intron occurs in the coding region of the mature peptide. Sequence analysis of upstream regions of MO-IH and MIH genes showed that they contained promoter elements with characteristics similar to other eukaryotic genes. These included sequences with high degrees of similarity to the arthropod initiator, TATA box and cAMP response element binding protein. Additionally, putative CF1/USP and Broad Complex Z2 transcription factor elements were found in the upstream regions of MIH and MO-IH genes respectively. The implications of the presence of the latter two putative transcription factor binding-elements for control of expression of MIH and MO-IH genes is discussed. Phylogenetic analysis and gene organisation show that MO-IH and MIH genes are closely related. Their relationship suggests that they represent an example of evolutionary divergence of crustacean hormones.

Crustacean ecdysteriods in reproduction and embryogenesis

Ecdysteroids are the molting hormones in Crustacea, as in other arthropods. They also subserve functions in the control of reproduction and embryogenesis. The available evidence indicate that the ecdysteroids are sequestered into the ovary by binding to yolk precursor proteins. Steroidogenic ability of the ovary is yet to be demonstrated in Crustacea. Despite several investigations, the role of ecdysteroids in oocyte maturation is not fully known. However, the embryonic ecdysteroids undergo significant fluctuation, correlated to specific developmental stages, including the secretion of embryonic envelopes and cuticle. Ecdysteroid metabolism in the eggs seems to be active throughout embryogenesis inasmuch as the free ecdysteroids are rapidly converted into conjugates, and vice versa; in addition to their inactivation into excretory ecdysteroidic acids. Eyestalk neuropeptides such as molt inhibiting hormones have a dominant role on the ecdysteroid synthesis by Y-organ, although recent evidence suggests a stimulatory role for yet another endocrine gland, the mandibular organ on Y-organ synthesis.

Ecdysteroids in relation to the molt cycle of the American lobster, Homarus americanus. II. excretion of metabolites

Ecdysteroid (Ecd) excretion patterns were followed during the molt cycle of adult male and female lobsters. Homarus americanus. Urine was the major route of Ecd elimination, amounting to greater than or equal to 96% of the excreted radioimmunoassay activity for all molt stages. The other identified route of Ecd elimination from the hemolymph was the feces, which accounted for the remaining 4% of the total Ecd excretion. High polarity metabolites (HP), including 20,26-dihydroxyecdysone (2026E) and 20-hydroxyecdysonoic acid (20EA), were the major types of Ecds found in the urine. Other urinary Ecd components included 20-hydroxyecdysone (20E), ecdysone (E), and ponasterone A (P). The major portion of urinary HP was composed of conjugates of 2026E, 20E, E, P, and other unidentified metabolites. The fecal Ecds were predominately HP and apolar metabolites. Apolar fecal Ecds were hydrolyzable to release 20EA, 2026E, 20E, E, P, and other metabolites. By means of intubation, [3H]E was placed directly into the cardiac stomach of lobsters. The gut pathway formed an apolar conjugate of [3H]E which was found exclusively in the feces. Lobsters are therefore capable of excreting ingested Ecds without absorption.

Ecdysteroids in the embryos and sera of the crabs, Cancer magister and C. anthonyi

Ecdysteroids in the embryos and sera of ovigerous brachyuran crabs, Cancer magister and C. anthonyi, were measured and characterized by radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC). C. magister embryos displayed a biphasic pattern of ecdysteroid fluctuation during development; titers decreased until mid embryogenesis and then increased and peaked prior to hatching. HPLC-RIA analysis indicated increasing ecdysone concentrations from mid embryogenesis to hatching. Endogenous biosynthesis of ecdysone by the embryos is suggested. In contrast, ecdysteroid titers in the embryos of C. anthonyi showed a steady decrease from very high initial concentrations. The decrease in titers of ecdysone and 20-hydroxyecdysone is suggestive of utilization of maternally derived ecdysteroids rather than endogenous biosynthesis during the shorter embryogenic period for C. anthonyi. Ecdysteroid concentrations did not differ with respect to location of the embryo within the egg mass. Serum ecdysteroids in C. magister females generally showed a monotonic pattern during brooding. However, for C. anthonyi females, increasing and decreasing titers were observed during the brood and interbrood periods, respectively. These fluctuations suggest mobilization of the ecdysteroids to the ovaries for subsequent storage and utilization during embryogenesis. The evolutionary significance of these differing patterns of ecdysteroid metabolism in these congeners is discussed.

Ecdysteroids in relation to the molt cycle of the American lobster, Homarus americanus. I. Hemolymph titers and metabolites

Hemolymph ecdysteroid (Ecd) titers were measured using radioimmunoassay (RIA) during the molt cycle of the American lobster, Homarus americanus. Individual animals showed small, transitory rises of Ecds which increased in magnitude with the onset of premolt and culminated in a large premolt peak at morphological stages D2(2)-D3(1). Male lobsters had significant postmolt peaks and late premolt titers that remained high until ecdysis. In females, postmolt peaks were absent and late premolt titers reached basal levels before ecdysis. At least seven different Ecd metabolites were identified by high-performance liquid chromatography-RIA analyses. High polarity products (HP) were the most abundant metabolites in virtually every molt stage. Titers of HP were significantly higher in males during late postmolt-early intermolt and in late premolt. Levels of 20-hydroxyecdysone (20E) were equivalent in both sexes and correlated with the morphological changes associated with premolt. Evidence was also obtained for the presence of ecdysone, ponasterone A, and other as yet unidentified metabolites. The pattern of Ecd metabolites in the hemolymph supports other data indicative of 20E as the major molting hormone. Metabolism of 20E is primarily toward more polar compounds, including conjugates.

Ecdysteroid fluctuations during embryogenesis in the giant freshwater prawn, Macrobrachium rosenbergii

Ecdysteroid levels during the embryogenesis of the giant freshwater prawn, Macrobrachium rosenbergii, were determined by radioimmunoassay and high-performance liquid chromatography. Ecdysteroids consisting of significant amounts of 20-hydroxyecdysone and high-polarity products (HPP) and lesser amounts of ecdysone and low-polarity products (LPP) were detected in mature ovaries and newly laid eggs. All ecdysteroid groups decreased gradually during the nauplius phase. With the formation of the compound eye and the appearance of the carapace and other body-like structures, marking morphogenesis to the zoeal stage, embryos showed the beginning of a continuous and dramatic increase in ecdysteroid concentrations sustained until larval hatchout. Ecdysteroid levels at hatchout were above 20-fold greater than ecdysteroid levels in newly laid eggs. More specifically, HPP and 20-hydroxyecdysone increased concomitantly, with a decrease in 20-hydroxyecdysone only at the end of the embryogenic period, while ecdysone and LPP levels remained low or undetectable. It may be postulated that the presence of ecdysteroids in ovaries and eggs represents a reserve of maternal ecdysteroids which are necessary at the commencement of embryonic development; with the differentiation of embryonic tissue capable of ecdysteroid synthesis, ecdysteroids increase rapidly to play a role in later embryonic development.

Hemolymph ecdysteroids and molt cycle in males and females of Siriella armata M-Edw. (Crustacea: Mysidacea): possible control by the MI-ME X-organ of the eyestalk

Hemolymph ecdysteroids were quantified by radioimmunoassay (RIA) at successive stages of the molt cycle in the mysid Siriella armata. Profiles showed a single peak during premolt, at stage D1 for males, and D2 for reproducing females who displayed ecdysteroid levels 10 times higher than males. Titers were also measured for individuals which had been molt inhibited by early electrocauterization of the eyestalk MI-ME X-organ. In the case of total inhibition of molt preparation, the ecdysteroid peak was suppressed. It was displaced toward the end of the cycle when only ecdysis was inhibited. Ecdysone and 20-hydroxyecdysone were characterized in the hemolymph of both sexes using high-pressure liquid chromatography followed by RIA. High-polarity products, abundant in the female hemolymph, were resolved into 20-hydroxyecdysone and ecdysone by enzymatic hydrolysis and thin-layer chromatography. The quantitative and qualitative variations of ecdysteroid in the different situations (male or female, normal or inhibited cycles) are presented in relation to apolysis, epidermic activity, ecdysis, and secondary vitellogenesis in females, emphasizing the importance not only of ecdysteroids, but also of the MI-ME X-organ in monitoring molt and blood preparation in mysids.

Ecdysteroid levels during embryogenesis in the shrimp, Palaemon serratus (Crustacea Decapoda): quantitative and qualitative changes

During the embryogenesis of Palaemon serratus profound changes in ecdysteroid concentrations were found. Ecdysteroid concentrations increase at the appearance of the Y-organ and a slight decrease is observed just before hatching. Two peaks of ecdysteroid concentration occur between these two events if Palaemon is reared at 19 degrees, but only one broad maximum is observed after rearing at 11-12 degrees. The pattern of ecdysteroids changes during embryogenesis; the ecdysone level decreases, while the 20-OH-ecdysone concentration and the amount of high polarity products increase. During the embryonic stage C the ratio of 20-OH-ecdysone to ecdysone was shown by HPLC analysis to steadily increase. After enzymatic hydrolysis of high-polarity products the main RIA-positive material elutes from reversed-phase HPLC columns as 20-OH-ecdysone.

Changes in ecdysteroid and juvenile hormone titers correlated to the initiation of vitellogenesis in two Aedes species (Diptera, Culicidae)

Ecdysteroid and juvenile hormone titers were determined in the whole body of females of Aedes detritus and A. caspius. Since both hormones were assayed from the same extract, this method allowed determination of their simultaneous variations during egg formation, i.e., from the time the females emerged until the onset of oviposition. A drastic hormonal increase was observed at the beginning of vitellogenesis. This increase occurred as two high and sharp peaks, the first of ecdysteroids and the second, which took place 8 hr later, of juvenile hormones. The two peaks together lasted less than 12 hr, with the highest level at about 3 X 10(-7) mumol/mg fresh tissue. After the juvenile hormone peak, the oocytes entered into stage III/b, the time at which the intensive phase of vitellin accumulation in the eggs begins.