Vitellogenin synthesis in andrectomized males of the terrestrial isopod, Armadillidium vulgare (malacostracan Crustacea)

Feminising Wolbachia disrupt Armadillidium vulgare insulin-like signalling pathway

The endosymbiont Wolbachia feminises male isopods by making them refractory to the insulin-like masculinising hormone, which shunts the autocrine development of the androgenic glands. It was, therefore, proposed that Wolbachia silences the IR receptors, either by preventing their expression or by inactivating them. We describe here the two IR paralogs of Armadillidium vulgare. They displayed a conventional structure and belonged to a family widespread among isopods. Av-IR1 displayed an ubiquist expression, whereas the expression of Av-IR2 was restricted to the gonads. Both were constitutively expressed in males and females and throughout development. However, upon silencing, altered gland physiology and gene expression therein suggested antagonistic roles for Av-IR1 (androinhibiting) and Av-IR2 (androstimulating). They may function in tandem with regulating neurohormones, as a conditional platform that conveys insulin signalling. Wolbachia infection did not alter their expression patterns: leaving the IRs unscathed, the bacteria would suppress the secretion of the neurohormones, thus inducing body-wide IR deactivation and feminisation. Adult males injected with Wolbachia acquired an intersexed physiology. Their phenotypes and gene expressions mirrored the silencing of Av-IR1 only, suggesting that imperfect feminisation stems from a flawed invasion of the androstimulating centre, whereas in fully feminised males invasion would be complete in early juveniles. TAKE AWAY: Two antagonistic Insulin Receptors were characterised in Armadillidium vulgare. The IRs were involved in androstimulating and androinhibiting functions. Wolbachia-induced feminisation did not prevent the expression of the IRs. Imperfectly feminised intersexes phenocopied the silencing of Av-IR1 only. Wolbachia would deactivate the IRs by suppressing neurosecretory co-factors.

Protandrous Hermaphroditic Reproductive System in the Adult Phases of Mothocya renardi (Bleeker, 1857) (Cymothoidae: Isopoda: Crustacea) -Light and Electron Microscopy Study

The reproductive system of Mothocya renardi (Bleeker, 1857), a protandrous hermaphroditic cymothoid that infects the belonid fish Strongylura leiura Bleeker, 1850, is characterized using light and electron microscopy. Three protandrous hermaphroditic adult phases are identified: male, transitional and female. Each phase includes a paired reproductive system, one on either side of the gut. Each consists of three lobed testes, followed by an ovary, then a vas deferens that opens into a penis on the same side. During the male phase, all testis lobes are filled with germ cells at various stages of spermatogenesis and spermeogenesis. Primary and secondary spermatogonial cells are confined to the peripheral side of the testis lobe. The ovary shows peripheral germarium and a large number of yolkless oocytes encircled by follicle cells. The oviduct emerged from the ovary mid laterally and its distal end was found to be sealed. The exceptionally elongated spermatozoon consists of a head and a long filamentous tail. The spermatozoa are found organized into characteristic bundles to form spermatophores, and these are also packed in the vas deferens during the male phase. During the transitional phase, on the other hand, testes appear to be withered, but the vas deferens contains spermatophores. The ovary shows yolky oocytes encircled by follicle cells. During the female phase, the testis lobes appear as thin, empty, and sac like, and the extremity of the vas deferens is closed. Ovaries contain yolky oocytes and more prominent oviducts than male and transitional phases. The present paper also discusses the pattern of correlation between 1) the ovarian and brood cycles and 2) the ovarian and molt cycles.

Vitellogenin2: spermatozoon specificity and immunoprotection in mud crabs

As the precursor of vitellin (Vn), vitellogenin (Vg) has initially been considered as a female-specific protein involved in vitellogenesis, while it was also present in males induced by hormones or organs manipulation. Distinct from vtg1 we previously found in female mud crab Scylla paramamosain, vtg2 was intriguingly detected in male testis under normal physiological conditions in this study. Sequence analysis showed that vtg2 and vtg1 were actually two isoforms of Vg caused by different types of alternative splicing. PCR and in situ hybridization analysis revealed that vtg2 was localized only in the testicular spermatozoa, while Vn was detected in both the spermatozoa of the testis and seminal vesicle. Therefore, we speculated that Vn was initially translated in testicular spermatozoa, then migrated with spermatozoa, and finally stored in the seminal vesicle, where spermatozoa gradually accomplished maturation. We presumed that vtg2/Vn might act as an immune-relevant molecule in the male reproduction system. In the subsequent experiment, the expression of vtg2/Vn in testis was significantly induced in response to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) injection at both transcriptional and translational levels. In the light of the results presented above, we deemed that vtg2/Vn is a novel candidate of immune-relevant molecules involved in immunoprotection during the spermatozoon maturation, and this research helps to open a new avenue for further exploring the role of Vg.

Molecular characterization of insulin-like androgenic gland hormone-binding protein gene from the oriental river prawn Macrobrachium nipponense and investigation of its transcriptional relationship with the insulin-like androgenic gland hormone gene

Insulin-like androgenic gland hormone-binding protein (IAGBP) has been investigated in crustaceans in vitro. However, the relationship between IAGBP and its putative binding protein partner insulin-like androgenic gland hormone (IAG) has not been studied at the transcriptional level in vivo. In the current study, we cloned the full-length cDNA of IAGBP from the oriental river prawn Macrobrachium nipponense (Mn-IAGBP) and investigated the transcriptional patterns of Mn-IAGBP and the M. nipponense IAG gene (Mn-IAG) at different developmental stages and in different tissues. Mn-IAGBP mRNA was detected in all examined tissues from adult male prawns, with the highest transcriptional levels in the testis. Mn-IAG mRNA was detected in the androgenic gland and hepatopancreas. The genomic sequences of Mn-IAGBP and Mn-IAG were isolated by genome walking and two gene copies were found in both Mn-IAGBP and Mn-IAG. The relationship between Mn-IAGBP and Mn-IAG at the transcriptional level was studied by RNA interference. Injection of Mn-IAGBP double-stranded RNA (dsRNA) significantly reduced the transcription of Mn-IAG, while injection of Mn-IAG dsRNA significantly reduced the transcription of Mn-IAGBP in testis, muscle, androgenic gland, and hepatopancreas. These results demonstrate the involvement of the IAGBP gene in IAG signaling in M. nipponense.

Molecular characterization and expression analysis of an insulin-like gene from the androgenic gland of the oriental river prawn, Macrobrachium nipponense

The androgenic gland (AG), a male-specific endocrine organ in crustacean, is responsible for the maintenance of male characteristics and gender differentiation. In this study, an AG-specific gene, the Macrobrachium nipponesne insulin-like androgenic gland factor (MnIAG) was isolated from a transcriptome library of M. nipponesne and its full-length cDNA sequences were obtained by RACE method. The cDNA was 1,547 bp in length and encoded a precursor protein of 175 amino acids. The deduced precursor protein consisted of a signal peptide, B chain, C peptide and an A chain, which exhibited the same structural organization as that of previously identified insulin-like androgenic gland in crustacean. The mature peptide of the MnIAG owned two additional conserved cysteine residues, which were also found in the Palaemonidae species reported. Results of the tissue distribution and in situ hybridization showed the MnIAG expressed exclusively in androgenic gland. The quantitative RT-PCR results demonstrated that the MnIAG transcript was present at blastula stage and later developmental stages with low levels, which suggested that the primordial cells of the AG might form at these stages.

Vitellogenin-like proteins in the freshwater amphipod Gammarus fossarum (Koch, 1835): functional characterization throughout reproductive process, potential for use as an indicator of oocyte quality and endocrine disruption biomarker in males

This work focused on the validation of biological specificity of the quantitative LC-MS/MS assay by checking the natural variability of Vg levels during the reproductive cycle in Gammarus fossarum (i.e., including oogenesis and embryogenesis). Laboratory tests were performed for 21 days under controlled conditions to assess Vg changes in male and female gammarids after exposure to chemical stress. Females were exposed to two crustacean hormones, 20-hydroxyecdysone (0.01, 1 and 100 μg L⁻¹) and methyl-farnesoate (0.01, 1 and 100 μg L⁻¹). No effect was recorded for 20-hydroxyecdysone, whereas in females exposed to methyl-farnesoate a deleterious impact on Vg production was observed. Males were exposed to crustacean hormones 20-hydroxyecdysone (0.01, 1 and 100 μg L⁻¹) and methyl-farnesoate (0.01, 1 and 100 μg L⁻¹), the insecticide methoxyfenozide (0.001, 0.1 and 10 μg L⁻¹), the fungicide propiconazole (0.001, 0.1, 10 and 1000 μg L⁻¹), and the pharmaceutical products benzophenone, carbamazepine, cyproterone, and R-propranolol (0.001, 0.1, 10 and 1000 μg L⁻¹). Induction of Vg synthesis was recorded in males exposed to cyproterone, methoxyfenozide, methyl-farnesoate, and propiconazole. Finally, we validated the function of the ILIPGVGK peptide used to track vitellogenin in G. fossarum across reproductive processes (vitellogenesis and embryogenesis), and results confirmed the energy reserve role of Vg during embryo development. We show that oocyte surface measurement is directly related to Vg levels in the oocyte, constituting a reliable indicator of egg quality in G. fossarum. Consequently, it could be used as a reliable tool for biomonitoring programs. We recorded induction of Vg in male G. fossarum; however, the possible use of this tool as a specific biomarker of exposure to endocrine disruption should be confirmed in further studies.

The insulin-like androgenic gland hormone in crustaceans: From a single gene silencing to a wide array of sexual manipulation-based biotechnologies

Due to the over-harvesting and deterioration of wild populations, the ever-growing crustacean market is increasingly reliant on aquaculture, driving the need for better management techniques. Since most cultured crustacean species exhibit sexually dimorphic growth patterns, the culture of monosex populations (either all-male or all-female) is a preferred approach for gaining higher yields, with the ecological benefit of reducing the risk of invasion by the cultured species. Sexual manipulations may also render sustainable solutions to the environmental problems caused by the presence of invasive crustacean species with detrimental impacts ranging from aggressive competition with native species for food and shelter, to affecting aquaculture facilities and harvests and causing structural damage to river banks. Recent discoveries of androgenic gland (AG)-specific insulin-like peptides (IAGs) in crustaceans and the ability to manipulate them and their encoding transcripts (IAGs) have raised the possibility of sexually manipulating crustacean populations. Sexual manipulation is already a part of sustainable solutions in fish aquaculture and in the bio-control of insect pest species, and attempts are also being made to implement it with crustaceans. As recently exemplified in a commercially important prawn species, IAG silencing, a temporal, non-genetically modifying and non-transmissible intervention, has enabled the production of non-breeding all-male monosex populations that are the progeny of sexually reversed males ('neo-females'). IAG manipulations-based biotechnologies therefore have the potential to radically transform the entire industry. We review here how this proof of concept could be broadened to meet both aquacultural and environmental needs. We include the major cultured decapod crustacean groups and suggest a sustainable solution for the management of invasive and pest crustacean species. We also review the key considerations for devising a biotechnological approach that specifically tailors the molecular technological abilities to the management of each target group.

From the discovery of the crustacean androgenic gland to the insulin-like hormone in six decades

Over the past six decades, a unique crustacean endocrine organ, the androgenic gland (AG), has occupied the minds of groups researching Crustacea the world over. Unlike male sexual differentiation and maintenance of sexual characteristics in other arthropods, in crustaceans these processes are regulated by the unique male AG. Crustaceans present a particular case in which the gametogenic organ (testis) is clearly separated from the organ regulating sex differentiation (the AG), enabling endocrine manipulations. The AG was first discovered in a decapod species and later investigated in detail not only in decapods but also in amphipods and isopods. The key role of the AG in regulating sex differentiation was subsequently validated in a number of representative species of a wide array of Malacostraca. It was in an isopod species that the AG hormone was first discovered. Later, orthologous genes were found in isopods and decapods, with all these genes sharing the key features of the insulin-like superfamily of peptides. This review unfolds the story of the AG and AG-specific insulin-like factors (IAGs) from a historical perspective, highlighting the main achievements in the field and giving a glimpse of future challenges to be addressed.

Vitellogenin-like gene expression in freshwater amphipod Gammarus fossarum (Koch, 1835): functional characterization in females and potential for use as an endocrine disruption biomarker in males

The induction of vitellogenin (Vtg) synthesis is widely accepted as a biomarker of estrogenic exposure in male and juvenile fish. Vtg synthesis has emerged as an interesting endpoint to assess endocrine disruptor (ED) effects in crustaceans. However, studies reporting induction of Vtg in male crustaceans are lacking. This study investigated the expression of the Vtg gene in a freshwater amphipod, Gammarus fossarum, using calibrated real-time reverse transcription polymerase chain reaction (real-time RT PCR). First, we described the basal pattern of expression in healthy male and female organisms at different reproductive moult stages, in order to validate the function of this gene. Females expressed from 200 to 700 times more Vtg transcripts than males, depending on the female reproductive stage. Females displayed significant elevation of Vtg mRNA levels at the end of the inter-moult phase and at the beginning of the pre-moult phase. Second, male gammarids were exposed to the estrogenic compound nonylphenol (NP) (0.05, 0.5, 5 and 50 μg L(-1)) and to the anti-androgen cyproterone (1, 10, 100 and 1000 μg L(-1)) for 2, 4, 8 and 16 days. Both chemicals altered the pattern of interindividual variability of Vtg gene expression in males with strong induction in some individuals. Finally, the impact of urban wastewater treatment plants (WWTP) on male Vtg gene expression was assessed in organisms transplanted in the field during in situ bioassay campaigns in three different watersheds. Induction of the Vtg mRNA level was observed in males transplanted downstream from WWTP effluent discharge in two of the three study sites.

Crustacean endocrine toxicology: a review

Crustaceans are major constituents to aquatic ecosystems that provide a variety of ecological and economic services. Individual crustacean species are adept at occupying diverse niches and their success, in part, stems from neuro-endocrine signaling cascades that regulate physiology in response to environmental and internal cues. Peptide hormones are major signal transducers in crustaceans. The crustacean hyperglycemic hormone family of peptides regulates various aspects of growth, reproduction, and metabolism. These peptides may function as the terminal hormone to regulate some physiological activities or may function as intermediates in a signaling cascade. Ecdysteroids and terpenoids are two major classes of terminal signaling molecules in these cascades. Hormones from these two classes function independently or in concert to regulate various processes. Ecdysteroid signaling is subject to toxicological disruption through disturbances in ecdysteroid synthesis or binding of toxicants to the ecdysteroid receptor. Methyl farnesoate is the major terpenoid hormone of crustaceans and also is susceptible to disruption by environmental chemicals. However, the methyl farnesoate signaling pathway is poorly understood and only limited mechanistic confirmation for disruption of this endocrine signaling pathway exists. Disruption of the ecdysteroid/terpenoid signaling pathways in crustaceans has been associated with aberrations in growth, metamorphosis, reproductive maturation, sex determination, and sex differentiation. Population studies have revealed disruptions in crustacean growth, molting, sexual development, and recruitment that are indicative of environmental endocrine disruption. However, environmental factors other that pollution (i.e., temperature, parasitism) also can elicit these effects and definitive causal relationships between endocrine disruption in field populations of crustaceans and chemical pollution is generally lacking.

Dynamics of vitellogenin synthesis in juvenile giant freshwater prawnMacrobrachium rosenbergii

The dynamics of vitellogenin (Vg) mRNA expression and patterns of Vg and vitellin distribution in the hepatopancreas and ovary of juvenile Macrobrachium rosenbergii were examined using real-time RT-PCR and immunohistochemical methods. Eyestalk ablation was seen to induce rapid development of the gonads and Vg synthesis in females. In the female hepatopancreas, Vg mRNA expression was observed several days following ablation, after which levels increased gradually with increasing gonadosomatic index (GSI). Vitellin accumulation in the oocytes also increased with increasing Vg mRNA synthesis; expression was however negligible in the ovary. Hemolymph Vg levels in females ranged from 0.04 to 2.2 mg/ml. SDS PAGE/Western blotting analysis of hemolymph samples revealed that juvenile Vg was composed of 199 and 90 kDa subunits; the 102 kDa subunit present in adult female Vg (Okuno et al., 2002. J Exp Zool 292:417-429) could not be detected at any stage of vitellogenesis in juveniles. Vg was not detectable in non-ablated juveniles. The results of this study confirmed that the mode of involvement of eyestalk factors in regulating vitellogenesis is intrinsic to both juveniles and adults, and that a basic pattern of Vg synthesis and processing is conserved. However, the fact that juveniles are not able to produce the same Vg levels observed in adult females, and do not reach high GSI levels culminating in spawning suggests that other factors and physiological conditions specific to adult females are necessary to demonstrate full reproductive ability.

Expression of the Reproductive Female-Specific Vitellogenin Gene in Endocrinologically Induced Male and Intersex Cherax quadricarinatus Crayfish1

In oviparous females, the synthesis of the yolk precursor vitellogenin is an important step in ovarian maturation and oocyte development. In decapod Crustacea, including the red-claw crayfish (Cherax quadricarinatus), this reproductive process is regulated by inhibitory neurohormones secreted by the endocrine X-organ-sinus gland (XO-SG) complex. In males, the C. quadricarinatus vitellogenin gene (CqVg), although present, is not expressed under normal conditions. We show here that endocrine manipulation by removal of the XO-SG complex from male animals induced CqVg transcription. The CqVg gene was expressed differentially during the molt cycle in these induced males: no expression was seen in the intermolt stages, but expression was occasionally detected in the premolt stages and always detected in the early postmolt stages. Relative quantitation with a real-time reverse transcriptase-polymerase chain reaction showed that expression of CqVg in induced early postmolt males was an order of magnitude lower than that in reproductive females, a finding that was consistent with RNA in situ hybridization results. The SDS-PAGE of high-density lipoproteins from the hemolymph of endocrinologically induced early postmolt males did not show the typical vitellogenin-related polypeptide profile found in reproductive females. On the other hand, removal of the XO-SG complex from intersex individuals, which are chromosomally female but functionally male and possess an arrested female reproductive system, induced the expression, translation, and release of CqVg products into the hemolymph, as was the case for vitellogenic females. The expression of CqVg in endocrinologically manipulated molting males and intersex animals provides an inducible model for the investigation and understanding of the endocrine regulation of CqVg expression and translation in Crustacea as well as the relationship between the endocrine axes regulating molt and reproduction.

High-density lipoprotein associated with secondary vitellogenesis in the hemolymph of the crayfish Cherax quadricarinatus

The high-density lipoproteins LPI and LPII were isolated from the hemolymph of the crayfish Cherax quadricarinatus by gradient ultracentrifugation and high-performance liquid chromatography (HPLC). Both lipoproteins contained a carotenoid moiety. LPI is comprised of a single polypeptide with an approximate molecular mass of 96 kDa. LPII was composed of two similar native components, LPIIa and LPIIb, both having polypeptides of 80 and 177 kDa. Both under natural conditions and after endocrine manipulations, LPI was present in males and in females, regardless of the female reproductive stage. LPII was present only in secondary-vitellogenic females, but not during the winter reproductive arrest period. LPII was also absent from young females that had received androgenic gland implants. LPII also appeared in the hemolymph of intersex individuals from which the androgenic gland had been removed. It is therefore suggested that LPII serves as a marker indicating the onset of secondary vitellogenesis in C. quad'iariicarintus females.

Androgenic gland hormone is a sex-reversing factor but cannot be a sex-determining factor in the female crustacean isopods Armadillidium vulgare

Sex reversal of female isopods, Armadillidium vulgare, has been induced by implantation of the androgenic gland (AG) into individuals after the initiation of morphological sex differentiation. The focus of the present study is to examine whether female gonads are reversed by the androgenic gland hormone (AGH) during the sexually undifferentiated period through postembryonic development in A. vulgare. Instead of injections of AGH, three AGs were implanted into each genetic female at various developmental stages to induce sex reversal. Before implantation fresh AGs were treated with ethanol to stop AGH synthesis, but then still contained AGH. These AGs have been referred to as ethanol-treated AGs (t-AGs). Development of a testis was used as an indicator of gonadal sex reversal. The gonads of genetic females were transformed into testes by implantations of t-AGs during the sex differentiation period. However, when genetic females received implants at sexually undifferentiated stages, development of their gonads was not reversed in the male direction. These results suggest that after the onset of gonadal sex differentiation, AGH is a sex-reversing factor that can turn a female gonad into a male gonad. AGH cannot be a sex-determining factor in female A. vulgare, as undifferentiated gonads of genetic females are not sex reversed by the hormone.

Sex reversal by implantations of ethanol-treated androgenic glands of female isopods, Armadillidium vulgare (Malacostraca, crustacea)

The androgenic glands (AGs) of malacostracan crustaceans are responsible for differentiation of male sexual characteristics, and sex reversal is readily obtained by implantation of AGs in female crustaceans. In order to induce sex reversal, we implanted inactive AGs (dead cells) into young females of Armadillidium vulgare. Before implantation fresh AGs (living cells) were treated twice with 80% ethanol for 3 min and kept in crustacean physiological saline for 30 s. We refer to these AGs as ethanol-treated AGs (t-AGs). Stage 6 females were used as recipients of t-AG implantation. They received an implant of three t-AGs (3 t-AGs) three times, once each week. Testis formation in recipients was used as an indicator of the masculinized levels of female gonads. Female sexual characteristics were masculinized in proportion to the number of 3 t-AG implantations. Three implantations (total number of t-AGs, nine glands) induced development of testes, penes, and male copulatory organs in the recipient females. Furthermore, they could produce progeny. These results show that t-AG implantations are capable of inducing masculinization of female sexual characteristics. The procedure of three implantations with 3 t-AGs at stage 6 is enough to transform the sex from a genetic female into a functional male. If t-AGs are used to implant instead of fresh AGs, we can detect the effects induced by newly formed AGs of recipient females, not by implanted donor's AGs. The present method may be useful for examining the regulatory mechanism of sex differentiation of female A. vulgare.

Isolation and characterization of the female-specific protein (vitellogenin) in mature female hemolymph of the freshwater prawn, Macrobrachium rosenbergii: comparison with ovarian vitellin

Purification and characterization of the female-specific protein (vitellogenin) from the hemolymph of mature female prawn, Macrobrachium rosenbergii, were the objectives of this study. The comparison of biochemical characteristics between vitellogenin and ovarian vitellin was also conducted. Hemolymph vitellogenin was purified with DEAE, hydroxylapatite, and another DEAE chromatographic column. The specific protein (vitellogenin) was shown in the fractions of chromatographic columns on the basis of ELISA, Western blotting, and immunoprecipitation. A purified vitellogenin was obtained with an apparent molecular weight of 700 kDa as determined by PAGE. The purified vitellogenin was considered as a lipoglycoprotein on the basis of staining data. Three subunits (170, 100, and 89 kDa) in purified vitellogenin and two subunits (100 and 89 kDa) in vitellin were detected with SDS-PAGE. Nondisulfide bonds were found in the binding of polypeptide subunits. Only the 89-kDa subunit was a glycopolypeptide in both vitellogenin and vitellin. The amino acid composition of vitellogenin differed from that of vitellin in a few amino acids. Eight amino acid sequences from the N-terminal end of 89- and 100-kDa subunits were determined and they were identical between vitellogenin and vitellin. Seven amino acid sequence from the N-terminal end of the 170-kDa subunit were also identical to the 100-kDa subunit. Purified vitellogenin was more susceptible to precipitation in a solution with low ionic strength than vitellin. This study suggests a close relationship between vitellogenin and vitellin in M. rosenbergii in their biochemical characteristics.

Sexual bipotentiality of developing ovaries in the terrestrial isopod Armadillidium vulgare (Malacostraca, Crustacea)

The androgenic glands (AG) of crustaceans are responsible for differentiation of male sexual characters. The process of gonadal differentiation in females was studied morphologically in Armadillidium vulgare given a masculinizing AG implant. Gonadal masculinization was induced by implantation of an AG into females at various stages of postembryonic development. Functional sex reversal always occurred when an AG was implanted into females that were in stages 5 and 6 of development. Partial formation of testes was induced after implantation of an AG into stage 7 and 8 females. When an AG was implanted into a stage 9 female, development of a functional testis was not observed, but the ovaries were partially masculinized. These results show that after the onset of sex differentiation female gonads retain sexual bipotentiality through several stages of postembryonic development. Implantation of one AG into a female is enough to induce gonadal masculinization and sex reversal in this species. The AG implant up to stage 6 (3.4 mm in body length) is an experimental procedure certain to transform a genetic female into a functional male. The process of gonadal development in female A. vulgare is discussed.

Ovarian control of oostegite formation in the terrestrial isopod, Armadillidium vulgare (Malacostraca, Crustacea)

The correlation between oostegite formation and ovarian maturation was investigated in the isopod Armadillidium vulgare. Females whose ovaries had been removed and males whose androgenic glands had been removed were used in these experiments. Ovariectomy of puberal females did not stop oostegite formation. Whether oostegites develop in puberal females whose ovaries have been removed depends upon the degree of maturation of the ovaries at the time of removal. On the other hand, ovariectomized juvenile females and andrectomized juvenile males were unable to form oostegites when they attained puberty. An extract of vitellogenic ovaries induced oostegite formation in ovariectomized females and andrectomized males, but not in intact males. The ability of ovarian extracts to induce oostegite formation was dose-dependent. The nature of this ovarian factor that induces oostegite formation in A. vulgare remains to be elucidated.

Sex-reversal of male Armadillidium vulgare (Isopoda, Malacostraca, Crustacea) following andrectomy and partial gonadectomy

Evidence is presented for the first time for the complete sex-reversal of genetic males of the terrestrial isopod Armadillidium vulgare into functional females following partial gonadectomy. Fifth-instar males were used. The anterior half of their rudimentary reproductive organs along with the attached androgenic glands were removed. Six months later these animals formed oostegites and laid eggs, and when bred with normal males, produced only male offspring. These results show that in the absence of the androgenic gland, female sex characteristics differentiate and oogenesis occurs in genetic males.