Effects of estradiol and progesterone on the reproduction of the freshwater crayfish Cherax albidus

Evaluation of the Role of Soybean Lecithin, Egg Yolk Lecithin, and Krill Oil in Promoting Ovarian Development in the Female Redclaw Crayfish Cherax quadricarinatus

The optimal supplementation of lipid nutrients in the diet showed crucial physiological functions in gonadal development and maturation in adult female aquatic animals. Four isonitrogenous and isolipidic diets with no extra lecithin supplementation (control), 2% soybean lecithin (SL), egg yolk lecithin (EL), or krill oil (KO) supplementation were formulated for Cherax quadricarinatus (72.32 ± 3.58 g). Ovary development and physiological characteristics of crayfish were evaluated after a 10-week feeding trial. The results indicated that SL, EL, or KO supplementation all significantly increased the gonadosomatic index, especially in the KO group. Crayfish fed the diet with SL showed the highest hepatosomatic index compared with those fed the other experimental diets. KO was more efficient than SL and EL in promoting triacylglycerol and cholesterol deposition in the ovary and hepatopancreas but also showed the lowest concentration of low-density lipoprotein cholesterol in the serum. KO significantly increased yolk granule deposition and accelerated oocyte maturation than other experimental groups. Furthermore, dietary phospholipids significantly enhanced the gonad-stimulating hormone concentration in the ovary and reduced the secretion of gonad-inhibiting hormones in the eyestalk. KO supplementation also significantly improved organic antioxidant capacity. From the ovarian lipidomics results, phosphatidylcholine and phosphatidylethanolamine are two main glycerophospholipids that respond to different dietary phospholipids. Polyunsaturated fatty acids (especially C18:2n-6, C18:3n-3, C20:4n-6, C20:5n-3, and C22:6n-3) were pivotal participants during ovarian development of crayfish regardless of lipid type. Combined with the ovarian transcriptome, the best positive function of KO was due to activated steroid hormone biosynthesis, sphingolipid signaling, retinol metabolism, lipolysis, starch and sucrose metabolism, vitamin digestion and absorption, and pancreatic secretion. As a consequence, dietary supplementation with SL, EL, or KO all improved the ovarian development quality of C. quadricarinatus, especially KO, which was the optimum choice for promoting ovary development in adult female C. quadricarinatus.

Characterization, expression, and function of the pyrokinins (PKs) in the giant freshwater prawn, Macrobrachium rosenbergii

Pyrokinins (PKs) are neuropeptides that have been found to regulate a variety of physiological activities including reproduction in various insect and crustacean species. However, the reproductive roles of PKs in the giant freshwater prawn have not yet been investigated. In this study, we identified the MroPK gene from next-generation sequence resources, which encodes a MroPK precursor that shares a high degree of conservation with the C-terminal sequence of FxPRLamide in other arthropods. MroPK is expressed within most tissues, except the hepatopancreas, stomach, and gill. Within developing ovarian tissue, MroPK expression was found to be significantly higher during the early stages (stages 1-2) compared with the late stages (stages 3-4), and could be localized to the oogonia, previtellogenic, and early vitellogenic oocytes. A role for PK in M. rosenbergii reproduction was supported following experimental administration of MroPK to ovarian explant cultures, showing an increase in the productions of progesterone and estradiol and upregulation of steroidogenesis-related genes (3β-HSD and 17β-HSD) and vitellogenin (Vg) expressions. Together, these results support a role for MroPK in regulating ovarian maturation via steroidogenesis.

Xenobiotics Result in Hormonal and Enzymatic Dysregulations in the Red Mussel Mytilus galloprovincialis (Lamarck, 1819) (Bivalvia, Mytilidae)

<b>Background and Objective:</b> The contaminants in a marine ecosystem like mercury and synthetic hormones can disrupt the regulation of natural endocrine and reproductive systems of most organisms. This study aims to study the effect of organic and inorganic mercury on the viscera of <i>Mytilus galloprovincialis</i> after intracoelomic injection of 17α-ethinylestradiol, 17β-estradiol and Dichlorodiphenyltrichloroethane (DDT) and check the histological changes in the gonads. <b>Materials and Methods:</b> Mussels are collected during June-August, 2018 from Ras el tin beach of the Mediterranean Sea of Alexandria, Egypt. This study aims to: test the effect of 17α-ethinylestradiol, 17β-estradiol and DDT on vitellogenin (VTG) synthesis, enzymes dysfunction through intracoelomic injection of methyl mercury in a 0.75 μg/0.1 mL and mercury chloride to a 75 μg/0.1 mL. Gonads are studied histologically in control and treated mussels. Water-administered E2 and EE2 at 120 μL dose induced VTG expression in males 14 days exposure. <b>Results:</b> The relative concentration of VTG in the induced groups increases significantly as compared to the control. Alterations in the gonadal tissues and the maturation stages of the mussels are observed. The imposex mussels are characterized by concomitant secondary male sexual characteristics and the female gonad shows testicular structure. Superoxide Dismutase (SOD) activity in mussel digestive glands differed significantly (p = 0.002) after 72 hrs of MeHg exposure. <b>Conclusion:</b> Significant correlation can be observed between the activities of Glutathione S-Transferases (GST) and Glutathione Reductase (GR) in the digestive glands of mussels treated with MeHg, the enzyme activities of digestive glands treated with HgCl<sub>2</sub> and between Superoxide Dismutase<i>-</i>Catalase (SOD-CAT), SOD-GR and GST-GR.

Sex Hormones in Hemolymph of Red King Crabs from the Barents Sea

Simple Summary

Well-known sex hormones, testosterone and 17β-estradiol, play a crucial role in the reproduction of vertebrates. Biochemical assays have detected these substances in a few crustaceans, and it has been hypothesized that these hormones are involved in the regulation of crustacean reproduction. Red king crab is a large commercially important species harvested both in their native areas (North Pacific) and in the area of its introduction (Barents Sea). The presence of 17β-estradiol and testosterone and fluctuations of their concentrations in relation to different factors have not yet been investigated. For this reason, we provided a pilot study to reveal the levels of sex hormones in hemolymph of red king crabs captured in the coastal Barents Sea. These hormones were detected in the crabs and we compared our data with previously published data involving a wide range of crustaceans. We found seasonal variations in the level of testosterone with the maximum in the spawning period. Our data expand the current knowledge about the red king crab physiology and may be used for the development of its aquaculture.

Abstract

The presence of vertebrate-related steroid sex hormones has been reported in both freshwater and marine crustaceans. However, despite the commercial importance of king crabs, many aspects of their endocrinology are still unknown. For this reason, we examined hemolymph samples of the red king crab Paralithodes camtschaticus from the Barents Sea population for the presence of testosterone and 17β-estradiol using radioimmunoassay. The mean testosterone concentration was 0.46 ± 0.04 (range 0.08–1.39) ng mL^–1, whereas the mean 17β-estradiol concentration was 1248.9 ± 91.4 (range 217.7–4100.1) pg mL^–1. In general, the levels of 17β-estradiol and testosterone in red king crabs were higher than reported for the hemolymph of amphipods, crabs, and shrimps from warm and temperate waters, probably because the king crabs analyzed were larger and heavier than the other crustaceans. The concentrations of sex steroids did not differ significantly between males and females and between immature and mature red king crabs. Seasonal variations in the level of testosterone with the maximum value in the spawning period (May) indicate a potential role of the sex hormones in the maturation and reproduction processes of red king crab. Taking into account the slow growth rate in P. camtschaticus, our data could be useful not only for further physiological studies but also for the development of reliable techniques for red king crab aquaculture.

Comparative proteomics elucidates the dynamics of ovarian development in the Chinese mitten crab Eriocheir sinensis

Ovarian development is a complex physiological process for crustacean reproduction that is divided into the oogonium proliferation stage, endogenous vitellogenic stage, exogenous vitellogenic stage, and oocyte maturation stage. Proteomics analysis offers a feasible approach to reveal the proteins involved in the complex physiological processes of any organism. Therefore, this study performed a comparative proteomics analysis of the ovary and hepatopancreas at three key ovarian stages, including stages I (oogonium proliferation), II (endogenous vitellogenesis) and IV (exogenous vitellogenesis), of the Chinese mitten crab Eriocheir sinensis using a label-free quantitative approach. The results showed that a total of 2,224 proteins were identified, and some key proteins related to ovarian development and nutrition metabolism were differentially expressed. The 26 key proteins were mainly involved in the ubiquitin/proteasome pathway (UPP), cyclic AMP-protein kinase A (cAMP-PKA) signaling pathway, and mitogen-activated protein kinase (MAPK) signaling pathway during oogenesis. Fifteen differentially abundant proteins (DAPs) were found to participate in vitellogenesis and oocyte development, such as vitelline membrane outer layer protein 1 homolog, vitellogenin, vitellogenin receptor, heat shock 70 kDa protein cognate 3 and farnesyl pyrophosphate synthase. Forty-seven DAPs related to nutrition metabolism were identified, including the protein digestion, fatty acid metabolism, prostaglandin metabolism, lipid digestion and transportation, i.e. short-chain specific acyl-CoA dehydrogenase, acyl-CoA desaturase, fatty acid-binding protein, long-chain fatty acid CoA ligase 4, and hematopoietic prostaglandin D synthase. These results not only indicate proteins involved in ovarian development and nutrient deposition but also enhance the understanding of the regulatory pathways and physiological processes of crustacean ovarian development.

Identification of Sex-Related Genes from the Three-Spot Swimming Crab Portunus sanguinolentus and Comparative Analysis with the Crucifix Crab Charybdis feriatus

Simple Summary

Crabs within the family Portunidae are important marine species in both aquaculture and fishery sectors. The current aquaculture status of most portunids still relies on wild-caught fisheries due to the lack of essential knowledge regarding their reproductive biology and underlying governing mechanism. In the present study, we compared the differentially expressed genes (DEGs) between the different sexes of Portunus sanguinolentus based on their gonadal transcriptome profiles and subsequently contrasted them with the gonadal DEGs of Charybdis feriatus, the other member of the family Portunidae. In total, 40,964 DEGs between the ovaries and testes of P. sanguinolentus were uncovered, with 27,578 up-regulated and 13,386 down-regulated in females. After comparison, C. feriatus has approximately 63.5% of genes in common with P. sanguinolentus, with 62.6% showing similar expression patterns. Interestingly, the DMRT gene was specifically expressed in male P. sanguinolentus, while its homologous gene—doublesex (DSX)—was specifically expressed in male C. feriatus. The DEGs obtained from the gonadal transcriptome of P. sanguinolentus are a beneficial resource for future genetic and genomic research in P. sanguinolentus and its close species. The transcriptomic comparison analysis might provide references for better understanding the sex determination and differentiation mechanisms among portunids.

Abstract

Crabs within the family Portunidae are important marine species in both aquaculture and fishery sectors. The current aquaculture status of most portunids, however, still relies on wild-caught fisheries due to the lack of essential knowledge regarding their reproductive biology and underlying governing mechanism. With the advancement of sequencing technology, transcriptome sequencing has been progressively used to understand various physiological processes, especially on non-model organisms. In the present study, we compared the differentially expressed genes (DEGs) between sexes of Portunus sanguinolentus based on their gonadal transcriptome profiles and subsequently contrasted them with the gonadal DEGs of Charybdis feriatus, the other member of Family Portunidae. In total, 40,964 DEGs between ovaries and testes were uncovered, with 27,578 up- and 13,386 down-regulated in females. Among those, some sex-related DEGs were identified, including a dmrt-like (DMRT) gene which was specifically expressed in males. C. feriatus has approximately 63.5% of genes common with P. sanguinolentus, with 62.6% showing similar expression patterns. Interestingly, the DMRT gene was specifically expressed in male P. sanguinolentus while its homologous gene—doublesex (DSX)—was specifically expressed in male C. feriatus. The DEGs obtained from the gonadal transcriptome of P. sanguinolentus are a beneficial resource for future genetic and genomic research in P. sanguinolentus and its close species. The transcriptomic comparison analysis might provide references for better understanding the sex determination and differentiation mechanisms among portunids.

A Crab Is Not a Fish: Unique Aspects of the Crustacean Endocrine System and Considerations for Endocrine Toxicology

Crustaceans-and arthropods in general-exhibit many unique aspects to their physiology. These include the requirement to moult (ecdysis) in order to grow and reproduce, the ability to change color, and multiple strategies for sexual differentiation. Accordingly, the endocrine regulation of these processes involves hormones, receptors, and enzymes that differ from those utilized by vertebrates and other non-arthropod invertebrates. As a result, environmental chemicals known to disrupt endocrine processes in vertebrates are often not endocrine disruptors in crustaceans; while, chemicals that disrupt endocrine processes in crustaceans are often not endocrine disruptors in vertebrates. In this review, we present an overview of the evolution of the endocrine system of crustaceans, highlight endocrine endpoints known to be a target of disruption by chemicals, and identify other components of endocrine signaling that may prove to be targets of disruption. This review highlights that crustaceans need to be evaluated for endocrine disruption with consideration of their unique endocrine system and not with consideration of the endocrine system of vertebrates.

Ovarian development pattern and vitellogenesis of ridgetail white prawn, Exopalaemon carinicauda

The ridgetail white prawn Exopalaemon carinicauda has the potential to be used as a model organism in crustacean research because it has a transparent body, available draft genome, and short life cycle. However, their ovarian development pattern remains unclear under laboratory culture conditions. This study investigated the changes of ovarian external feature, ovarian histology, gonadosomatic index (GSI), and hepatosomatic index (HSI), as well as the expression and localization of vitellogenin in the ovary and the hepatopancreas during the first ovarian development cycle of E. carinicauda under laboratory-reared condition. The results demonstrated that (1) the first ovarian development cycle of E. carinicauda could be divided into 5 different stages in which the ovary changes its color from white to yellow during the vitellogenesis process in parallel with increasing GSI. (2) After pubertal molt, most females reached ovarian stage II while the females reached stage V after premating molt. (3) During the ovarian development, GSI increased smoothly and HSI relatively stable during the period of stages I to IV, while GSI increased but HSI decreased significantly from stages IV to V. (4) In situ hybridization (ISH) revealed that EcVg was slightly expressed in the oocyte cytoplasm of previtellogenic oocytes. The positive signal was mainly detected in hepatopancreatic fibrillar cells, and a strong signal was found in the hepatopancreas at stage IV. Moreover, the expression level of EcVg-mRNA in the hepatopancreas is stage-specific, and the hepatopancreas contributes majority of vitellin precursor protein to support the ovarian development of E. carinicauda.

Insights on Molecular Mechanisms of Ovarian Development in Decapod Crustacea: Focus on Vitellogenesis-Stimulating Factors and Pathways

Vitellogenesis in crustaceans is an energy-consuming process. Though the underlying mechanisms of ovarian maturation in decapod Crustacea are still unclear, evidence indicates the process to be regulated by antagonistically-acting inhibitory and stimulating factors specifically originating from X-organ/sinus gland (XO/SG) complex. Among the reported neuromediators, neuropeptides belonging to the crustacean hyperglycemic hormone (CHH)-family have been studied extensively. The structure and dynamics of inhibitory action of vitellogenesis-inhibiting hormone (VIH) on vitellogenesis have been demonstrated in several species. Similarly, the stimulatory effects of other neuropeptides of the CHH-family on crustacean vitellogenesis have also been validated. Advancement in transcriptomic sequencing and comparative genome analysis has led to the discovery of a large number of neuromediators, peptides, and putative peptide receptors having pleiotropic and novel functions in decapod reproduction. Furthermore, differing research strategies have indicated that neurotransmitters and steroid hormones play an integrative role by stimulating neuropeptide secretion, thus demonstrating the complex intertwining of regulatory factors in reproduction. However, the molecular mechanisms by which the combinatorial effect of eyestalk hormones, neuromediators and other factors coordinate to regulate ovarian maturation remain elusive. These multifunctional substances are speculated to control ovarian maturation possibly via the autocrine/paracrine pathway by acting directly on the gonads or by indirectly exerting their stimulatory effects by triggering the release of a putative gonad stimulating factor from the thoracic ganglion. Acting through receptors, they possibly affect levels of cyclic nucleotides (cAMP and cGMP) and Ca²⁺ in target tissues leading to the regulation of vitellogenesis. The "stimulatory paradox" effect of eyestalk ablation on ovarian maturation continues to be exploited in commercial aquaculture operations, and is outweighed by the detrimental physiological effects of this procedure. In this regard, the development of efficient alternatives to eyestalk ablation based on scientific knowledge is a necessity. In this article, we focus principally on the signaling pathways of positive neuromediators and other factors regulating crustacean reproduction, providing an overview of their proposed receptor-mediated stimulatory mechanisms, intracellular signaling, and probable interaction with other hormonal signals. Finally, we provide insight into future research directions on crustacean reproduction as well as potential applications of such research to aquaculture technology development.

Presence of serotonin and its receptor in the central nervous system and ovary and molecular cloning of the novel crab serotonin receptor of the blue swimming crab, Portunus pelagicus

Serotonin (5-HT) plays pivotal roles in many physiological processes including reproduction of crustaceans, which are mediated 5-HT receptors. The distributions of 5-HT and its receptor have never been explored in Portunus pelagicus. To validate the targets which indirectly indicate the roles of 5-HT in this crab, we have investigated the distribution of 5-HT in the central nervous system (CNS) and ovary using immunohistochemistry and tissue expression of its receptor by RT-PCR. In the brain, 5-HT immunoreactivity (-ir) was detected in clusters 6, 7, 8, 11, 14, 15 and the fibers. In the ventral nerve cord (VNC), 5-HT-ir was detected in pairs of neurons and the fibers connected to the neurons. In the ovary, 5-HT-ir was intense in the oocyte step 1 (Oc1) and Oc2, and its intensity was slightly decreased in Oc3 and Oc4. The 5-HT receptor was molecularly characterized to be type 7, and it was strongly expressed in the eyestalk, brain, VNC, mature ovary and muscle. Due to the presence of 5-HT receptor we suggest that 5-HT acts primarily at the CNS and ovary, thus implicating its role in reproduction especially in the development of oocytes though its exact function in this crab needed to be explored further.

Comparative transcriptome reveals the potential modulation mechanisms of estradiol affecting ovarian development of female Portunus trituberculatus

Estradiol is an important sex steroid hormone that is involved in the regulation of crustacean ovarian development. However, the molecular regulatory mechanisms of estradiol on ovarian development are largely unknown. This study performed transcriptome sequencing of ovary, hepatopancreas, brain ganglion, eyestalk, and mandibular organ of crabs after estradiol treatment (0.1μg g^-1 crab weight). A total of 23, 806 genes were annotated, and 316, 1300, 669, 142, 383 genes were expressed differently in ovary, hepatopancreas, brain ganglion, eyestalk, and mandibular organ respectively. Differentially expressed gene enrichment analysis revealed several crucial pathways including protein digestion and absorption, pancreatic secretion, insect hormone biosynthesis, drug metabolism-cytochrome P450 and signal transduction pathway. Through this study, some key genes in correlation with the ovarian development and nutrition metabolism were significantly affected by estradiol, such as vitelline membrane outer layer 1-like protein, heat shock protein 70, Wnt5, JHE-like carboxylesterase 1, cytochrome P302a1, crustacean hyperglycemic hormone, neuropeptide F2, trypsin, carboxypeptidase B, pancreatic triacylglycerol lipase-like, and lipid storage droplet protein. Moreover, RT-qPCR validation demonstrated that expression of transcripts related to ovarian development (vitelline membrane outer layer 1-like protein and cytochrome P302a1) and nutrition metabolism (trypsin, glucose dehydrogenase and lipid storage droplet protein) were significantly affected by estradiol treatment. This study not only has identified relevant genes and several pathways that are involved in estradiol regulation on ovarian development of P. trituberculatus, but also provided new insight into the understanding of the molecular function mechanisms of estradiol in crustacean.

De novo gonad transcriptome analysis of the common littoral shrimp Palaemon serratus: novel insights into sex-related genes

BACKGROUND

The common littoral shrimp Palaemon serratus is an economically important decapod resource in some European communities. Aquaculture practices prevent the genetic deterioration of wild stocks caused by overfishing and at the same time enhance the production. The biotechnological manipulation of sex-related genes has the proved potential to improve the aquaculture production but the scarcity of genomic data about P. serratus hinders these applications. RNA-Seq analysis has been performed on ovary and testis samples to generate a reference gonadal transcriptome. Differential expression analyses were conducted between three ovary and three testis samples sequenced by Illumina HiSeq 4000 PE100 to reveal sex-related genes with sex-biased or sex-specific expression patterns.

RESULTS

A total of 224.5 and 281.1 million paired-end reads were produced from ovary and testis samples, respectively. De novo assembly of ovary and testis trimmed reads yielded a transcriptome with 39,186 transcripts. The 29.57% of the transcriptome retrieved at least one annotation and 11,087 differentially expressed genes (DEGs) were detected between ovary and testis replicates. Six thousand two hundred seven genes were up-regulated in ovaries meanwhile 4880 genes were up-regulated in testes. Candidate genes to be involved in sexual development and gonadal development processes were retrieved from the transcriptome. These sex-related genes were discussed taking into account whether they were up-regulated in ovary, up-regulated in testis or not differentially expressed between gonads and in the framework of previous findings in other crustacean species.

CONCLUSIONS

This is the first transcriptome analysis of P. serratus gonads using RNA-Seq technology. Interesting findings about sex-related genes from an evolutionary perspective (such as Dmrt1) and for putative future aquaculture applications (Iag or vitellogenesis genes) are reported here. We provide a valuable dataset that will facilitate further research into the reproductive biology of this shrimp.

Molecular insights into ovary degeneration induced by environmental factors in female oriental river prawns Macrobrachium nipponense

The oriental river prawn, Macrobrachium nipponense, is an important breeding species in China. The ovary development of this prawn is regulated by the genetic factors and external environmental factors and has obvious seasonal regularity. However, the molecular mechanism of regulating ovary degradation in M. nipponense remains unclear. To address this issue, we performed transcriptome sequencing and gene expression analyses of eyestalks, cerebral ganglia (CG) and thoracic ganglia (TG) of female M. nipponense between the full ovary stage and degenerate ovary stage. Differentially expressed genes enrichment analysis results identified several important pathways such as "phototransduction-fly," "circadian rhythm-fly" and "steroid hormone biosynthesis secretion." In the period of ovarian degeneration, the expressions of Tim, Per2 and red pigment concentration hormone (RPCH) were significantly decreased in the eyestalk, CG and TG. And expression of 7 genes in the steroid synthesis pathway, including steryl-sulfatase, cytochrome P450 family 1 subfamily A polypeptide 1, estradiol 17β-dehydrogenase 2, glucuronosyltransferase, 3-oxo-5-alpha-steroid 4-dehydrogenase 1, estradiol 17-dehydrogenase 1 and estrone sulfotransferase was significantly decreased in the CG. Food and light signals affect the expression of clock genes and thereby decrease the expression of RPCH and the estradiol synthesis-related genes in the nervous system, which may be the main cause of ovarian degeneration in M. nipponense. The results will contribute to a better understanding of the molecular mechanisms of ovarian development regulation in crustaceans.

Effect of estradiol on hepatopancreatic lipid metabolism in the swimming crab, Portunus trituberculatus

Estradiol is an important sex steroid hormone that involved in regulation of animal lipid metabolism. However, the effect of estradiol on lipid metabolism in swimming crab (Portunus trituberculatus) is unclear. The present study investigated the effect of four concentrations of exogenous estradiol (0, 0.01, 0.1 and 1 μg g^-1 crab weight) on the expression levels of lipid metabolism-related genes, lipid composition and histology of hepatopancreas in the P. trituberculatus. The results showed that the mRNA levels of carnitine palmitoyltransferase I and II (CPT-I and CPT-II) increased significantly at the low concentrations (0.01 μg g^-1 and 0.1 μg g^-1), while decreased significantly in the highest concentration (1 μg g^-1). The mRNA levels of acyl-CoA oxidase (ACOX), fatty acid transport protein (FATP), fatty acid-binding protein (FABP), diacylglycerol acyltransferase 1 (DGAT1) and acetyl-CoA carboxylase (ACC) were significantly down-regulated. The transcripts of fatty acid synthase (FAS) and fatty acyl desaturase (FAD) decreased significantly only in 1 μg g^-1 treatment. All estradiol treatments (0.01, 0.1 and 1 μg g^-1) had significantly higher percentages of 20:4n6, 20:5n3 and 22:6n3, but lower percentages of total monounsaturated fatty acids and polar lipids than the control treatment (0 μg g^-1). Histological observations indicated the size of B cell became larger under estradiol treatment. The results indicated that estradiol promoted lipid catabolism in the hepatopancreas of P. trituberculatus.

Establishment and Characterization of a Novel Tissue-specific DNA Construct and Culture System with Potential for Avian Bioreactor Generation

Transgenic chickens are of great interest for the production of recombinant proteins in their eggs. However, the use of constitutive strong promoters or the tissue-specific ovalbumin promoter for the generation of the transgenic chickens have different drawbacks that have to be overcome in order to make chicken bioreactor an efficient production system. This prompted us to investigate the use of an alternative tissue-specific promoter, the vitellogenin promoter, which could overcome the difficulties currently found in the generation of chicken bioreactors. In the present work we establish and characterize a DNA construct consisting of a fragment of the 5´-flanking region of the chicken vitellogenin II gene cloned in a reporter vector. This construct is capable of showing the ability of the promoter to drive expression of a reporting gene in a tissue-specific manner and in a way that closely resembles physiologic regulation of vitellogenin, making it an ideal candidate to be used in the future for generation of avian bioreactors. Besides, we validate an in vitro culture system to test the performance of the DNA construct under study that could be used as a practical tool before generating any transgenic chicken. These results are important since they provide the proof of concept for the use of the vitellogenin promoter for future genetic modification of chickens bioreactors with improved characteristics in terms of quality of the recombinant protein produced.

Immunolocalization and changes of 17beta-estradiol during ovarian development of Chinese mitten crab Eriocheir sinensis' [corrected]

17beta-estradiol (E₂) is important for crustacean ovarian development. This study aims to investigate the distribution and change pattern of E₂ in the ovary, hepatopancreas, thoracic ganglion and brain ganglion as well as Vg-mRNA expression level during ovarian development of Chinese mitten crab Eriocheir sinensis. Results showed that strongly positive signals of E₂ were mainly distributed in follicle cells of ovaries for all developmental stages as well as oocyte cytoplasm of stages III to V ovaries. In hepatopancreas, the E₂-positive signal was mainly detected in the cytoplasm and nucleus of fibrillar cells and the nucleus of resorptive cells, while the maximum fluorescence intensity was observed in stage III hepatopancreas. On the contrary, the E₂ immunoreactivities in nervous tissues were relatively stable during ovarian development. Moreover, the changing pattern of E₂ concentration was similar within hemolymph, ovary and hepatopancreas during the ovarian development. From stages I to III, the E₂ content in three tissues increased significantly, then decreased gradually until stage V. As for the Vg-mRNA expression level in hepatopancreas and ovaries, an increasing trend was found in ovaries but no significant difference was detected during the period of ovarian stages III to V. Hepatopancreatic Vg-mRNA expression level increased significantly during stages I to IV and dramatically decreased at stage V. In conclusion, our study suggests that ovary, hepatopancreas, hemolymph and nervous tissues are the target organs of E₂ in E. sinensis and E₂ concentrations in different tissues are closely related to vitellogenesis in ovary and hepatopancreas during ovarian development.

Effects of atrazine on vitellogenesis, steroid levels and lipid peroxidation, in female red swamp crayfish Procambarus clarkii

Atrazine, a widely use herbicide, has been classified as a potential endocrine disruptor, especially for freshwater species. In this study, we tested the hypothesis that atrazine can affect reproduction in crayfish through dysregulation of vitellogenin expression and hormone synthesis. Adult female crayfish (Procambarus clarkii) were exposed during one month to atrazine at concentrations of either 1 or 5 mg/L. At the end of the exposure, ovaries, hepatopancreas, and hemolymph samples were harvested for analysis of vitellogenin expression and steroid hormone levels. Ovarian tissue was also sampled for both biochemical and histological analyses. Our results show that atrazine-exposed crayfish had a lower expression of vitellogenin in the ovary and hepatopancreas, as well as smaller oocytes, and reduced vitellogenin content in the ovary. Despite these effects, circulating levels of estradiol increased in females exposed to 5 mg/L of atrazine, showing that the inhibiting effect of atrazine on vitellogenin production was not related to a lower secretion of sexual steroids. Instead, some early stimulating effects of estradiol on vitellogenesis could have occurred, particularly in the hepatopancreas. On the other hand, atrazine caused a higher metabolic effort, in terms of lactate production, presumably triggered to provide the energy needed to face the unspecific stress produced by the herbicide. Lipid peroxidation was not affected by atrazine, but glutathione levels were significantly increased.

Three-dimensional organization of the brain and distribution of serotonin in the brain and ovary, and its effects on ovarian steroidogenesis in the giant freshwater prawn, Macrobrachium rosenbergii

The giant freshwater prawn, Macrobrachium rosenbergii, is an economically important crustacean species which has also been extensively used as a model in neuroscience research. The crustacean central nervous system is a highly complex structure, especially the brain. However, little information is available on the brain structure, especially the three-dimensional organization. In this study, we demonstrated the three-dimensional structure and histology of the brain of M. rosenbergii together with the distribution of serotonin (5-HT) in the brain and ovary as well as its effects on ovarian steroidogenesis. The brain of M. rosenbergii consists of three parts: protocerebrum, deutocerebrum and tritocerebrum. Histologically, protocerebrum comprises of neuronal clusters 6-8 and prominent anterior and posterior medial protocerebral neuropils (AMPN/PMPN). The protocerebrum is connected posteriorly to the deutocerebrum which consists of neuronal clusters 9-13, medial antenna I neuropil, a paired lateral antenna I neuropils and olfactory neuropils (ON). Tritocerebrum comprises of neuronal clusters 14-17 with prominent pairs of antenna II (AnN), tegumentary and columnar neuropils (CN). All neuronal clusters are paired structures except numbers 7, 13 and 17 which are single clusters located at the median zone. These neuronal clusters and neuropils are clearly shown in three-dimensional structure of the brain. 5-HT immunoreactivity (-ir) was mostly detected in the medium-sized neurons and neuronal fibers of clusters 6/7, 8, 9, 10 and 14/15 and in many neuropils of the brain including anterior/posterior medial protocerebral neuropils (AMPN/PMPN), protocerebral tract, protocerebral bridge, central body, olfactory neuropil (ON), antennal II neuropil (Ann) and columnar neuropil (CN). In the ovary, the 5-HT-ir was light in the oocyte step 1(Oc₁) and very intense in Oc₂-Oc₄. Using an in vitro assay of an explant of mature ovary, it was shown that 5-HT was able to enhance ovarian estradiol-17β (E₂) and progesterone (P₄) secretions. We suggest that 5-HT is specifically localized in specific brain areas and ovary of this prawn and it plays a pivotal role in ovarian maturation via the induction of female sex steroid secretions, in turn these steroids may enhance vitellogenesis resulting in oocyte growth and maturation.

Starvation Promotes Autophagy-Associated Maturation of the Ovary in the Giant Freshwater Prawn, Macrobrachium rosenbergii

Limitation of food availability (starvation) is known to influence the reproductive ability of animals. Autophagy is a lysosomal driven degradation process that protects the cell under metabolic stress conditions, such as during nutrient shortage. Whether, and how starvation-induced autophagy impacts on the maturation and function of reproductive organs in animals are still open questions. In this study, we have investigated the effects of starvation on histological and cellular changes that may be associated with autophagy in the ovary of the giant freshwater prawn, Macrobachium rosenbergii. To this end, the female prawns were daily fed (controls) or unfed (starvation condition) for up to 12 days, and the ovary tissue was analyzed at different time-points. Starvation triggered ovarian maturation, and concomitantly increased the expression of autophagy markers in vitellogenic oocytes. The immunoreactivities for autophagy markers, including Beclin1, LC3-II, and Lamp1, were enhanced in the late oocytes within the mature ovaries, especially at the vitellogenic stages. These markers co-localized with vitellin in the yolk granules within the oocytes, suggesting that autophagy induced by starvation could drive vitellin utilization, thus promoting ovarian maturation.

Elucidation of the role of estradiol and progesterone in regulating reproduction in the edible crab, Oziothelphusa senex senex

Vertebrate sex steroids are ubiquitous and important bioactive mediators for many physiological functions.

Gonadal transcriptomic analysis and differentially expressed genes in the testis and ovary of the Pacific white shrimp (Litopenaeus vannamei)

Background

The Pacific white shrimp (Litopenaeus vannamei) is the world’s most prevalent cultured crustacean species. However, the supply of high-quality broodstocks is limited and baseline information related to its reproductive activity and molecular issues related to gonad development are scarce. In this study, we performed transcriptome sequencing on the gonads of adult male and female L. vannamei to identify sex-related genes.

Results

A total of 25.16 gigabases (Gb) of sequences were generated from four L. vannamei gonadal tissue libraries. After quality control, 24.11 Gb of clean reads were selected from the gonadal libraries. De-novo assembly of all the clean reads generated a total of 65,218 unigenes with a mean size of 1021 bp and a N50 of 2000 bp. A search of all-unigene against Nr, SwissProt, KEGG, COG and NT databases resulted in 26,482, 23,062, 20,659, 11,935 and 14,626 annotations, respectively, providing a total of 30,304 annotated unigenes. Among annotated unigenes, 12,320 unigenes were assigned to gene ontology categories and 20,659 unigenes were mapped to 258 KEGG pathways. By comparing the ovary and testis libraries, 19,279 testicular up-regulated and 3,529 ovarian up-regulated unigenes were identified. Enrichment analysis of differentially expressed unigenes resulted in 1060 significantly enriched GO terms and 34 significantly enriched KEGG pathways. Nine ovary-specific, 6 testis-specific, 45 testicular up-regulated and 39 ovarian up-regulated unigenes were then confirmed by semi-quantitative PCR and quantitative real-time PCR. In addition, using all-unigenes as a reference, a total of 13,233 simple sequence repeats (SSRs) were identified in 10,411 unigene sequences.

Conclusions

The present study depicts the first large-scale RNA sequencing of shrimp gonads. We have identified many important sex-related functional genes, GO terms and pathways, all of which will facilitate future research into the reproductive biology of shrimp. We expect that the SSRs detected in this study can then be used as genetic markers for germplasm evaluation of breeding and imported populations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2219-4) contains supplementary material, which is available to authorized users.

De novo Transcriptome Analysis of Portunus trituberculatus Ovary and Testis by RNA-Seq: Identification of Genes Involved in Gonadal Development

The swimming crab Portunus trituberculatus is a commercially important crab species in East Asia countries. Gonadal development is a physiological process of great significance to the reproduction as well as commercial seed production for P. trituberculatus. However, little is currently known about the molecular mechanisms governing the developmental processes of gonads in this species. To open avenues of molecular research on P. trituberculatus gonadal development, Illumina paired-end sequencing technology was employed to develop deep-coverage transcriptome sequencing data for its gonads. Illumina sequencing generated 58,429,148 and 70,474,978 high-quality reads from the ovary and testis cDNA library, respectively. All these reads were assembled into 54,960 unigenes with an average sequence length of 879 bp, of which 12,340 unigenes (22.45% of the total) matched sequences in GenBank non-redundant database. Based on our transcriptome analysis as well as published literature, a number of candidate genes potentially involved in the regulation of gonadal development of P. trituberculatus were identified, such as FAOMeT, mPRγ, PGMRC1, PGDS, PGER4, 3β-HSD and 17β-HSDs. Differential expression analysis generated 5,919 differentially expressed genes between ovary and testis, among which many genes related to gametogenesis and several genes previously reported to be critical in differentiation and development of gonads were found, including Foxl2, Wnt4, Fst, Fem-1 and Sox9. Furthermore, 28,534 SSRs and 111,646 high-quality SNPs were identified in this transcriptome dataset. This work represents the first transcriptome analysis of P. trituberculatus gonads using the next generation sequencing technology and provides a valuable dataset for understanding molecular mechanisms controlling development of gonads and facilitating future investigation of reproductive biology in this species. The molecular markers obtained in this study will provide a fundamental basis for population genetics and functional genomics in P. trituberculatus and other closely related species.

The Y-organ secretory activity fluctuates in relation to seasons of molt and reproduction in the brachyuran crab, Metopograpsus messor (Grapsidae): Ultrastructural and immunohistochemical study

This paper presents a first-time report on the localization, structure and seasonal secretory activity of the Y-organ of a grapsid brachyuran crab (Metopograpsus messor). Having exhibited discrete seasonality with reference to the programming of molt and reproduction, this brachyuran crab has offered us an excellent model to obtain a clear picture of the fluctuating secretory nature of the Yorgan, all the way through the reproductive (August-December) as well as the molt-reproduction active (January-May) and inactive (June-July) seasons. Ultrastructural studies revealed that the secretion of the Y-organ was at its peak in premolt crabs during molt-reproduction season (January-May). Interestingly, the Y-organs of the intermolt females that engaged in breeding activity showed higher levels of secretion than those of the molt-reproduction inactive season (June-July), implicating the gland's involvement in reproduction. Immunohistochemical studies using the antiserum raised against 2-succinyl conjugate of ecdysone have demonstrated the ecdysteroid nature of the secretion from the Y-organ, and results of the quantitative assay of ecdysteroids (through radioimmunoassay) revealed that the hormone titer fluctuates in consonance with the Y-organ's secretory activity during seasons of molt and reproduction. Pertinently, not only that the paper gives us a comprehensive understanding on the secretory activity of the Y-organ in a season-dependent fashion, it also allows us to have a better insight into the gland's function related to molting and reproduction (for the first time) in a grapsid brachyuran crab.

Insights into hepatopancreatic functions for nutrition metabolism and ovarian development in the crab Portunus trituberculatus: gene discovery in the comparative transcriptome of different hepatopancreas stages

The crustacean hepatopancreas has different functions including absorption, storage of nutrients and vitellogenesis during growth, and ovarian development. However, genetic information on the biological functions of the crustacean hepatopancreas during such processes is limited. The swimming crab, Portunus trituberculatus, is a commercially important species for both aquaculture and fisheries in the Asia-Pacific region. This study compared the transcriptome in the hepatopancreas of female P. trituberculatus during the growth and ovarian maturation stages by 454 high-throughput pyrosequencing and bioinformatics. The goal was to discover genes in the hepatopancreas involved in food digestion, nutrition metabolism and ovarian development, and to identify patterns of gene expression during growth and ovarian maturation. Our transcriptome produced 303,450 reads with an average length of 351 bp, and the high quality reads were assembled into 21,635 contigs and 31,844 singlets. Based on BLASTP searches of the deduced protein sequences, there were 7,762 contigs and 4,098 singlets with functional annotation. Further analysis revealed 33,427 unigenes with ORFs, including 17,388 contigs and 16,039 singlets in the hepatopancreas, while only 7,954 unigenes (5,691 contigs and 2,263 singlets) with the predicted protein sequences were annotated with biological functions. The deduced protein sequences were assigned to 3,734 GO terms, 25 COG categories and 294 specific pathways. Furthermore, there were 14, 534, and 22 identified unigenes involved in food digestion, nutrition metabolism and ovarian development, respectively. 212 differentially expressed genes (DEGs) were found between the growth and endogenous stage of the hepatopancreas, while there were 382 DEGs between the endogenous and exogenous stage hepatopancreas. Our results not only enhance the understanding of crustacean hepatopancreatic functions during growth and ovarian development, but also represent a basis for further research on new genes and functional genomics of P. trituberculatus or closely related species.

Plasma sex steroid hormonal profile and gonad histology during the annual reproductive cycle of river catfish Hemibagrus nemurus (Valenciennes, 1840) in captivity

Plasma sex steroid hormonal profile and gonad histology were correlated to study the annual reproductive cycle of Hemibagrus nemurus. Hormones were measured by Enzyme Linked Immunosorbent Assay. Gonad tissues were observed by using light microscopy. The highest testosterone (T) value for male was observed in November and that of female was in October. 11-ketotestosterone (11-KT) and 17β-estradiol (E2) levels were highest in June and November, respectively. Hormonal profiles of T, 11-KT and E2 showed several peaks which indicated a non-seasonal pattern. There were significant differences (p < 0.05) in the monthly levels of T, 11-KT and E2. Gonadosomatic index of H. nemurus ranged from 1.14 ± 0.02 % to 7.06 ± 1.40 %, and high gonadosomatic indices were recorded in May, August and November. Gonad histology revealed that spermatozoa were always present in the testes which implied continuous spermatogenesis and asynchronous ovarian development pattern was observed in the ovaries. The annual reproductive cycle of H. nemurus did not show a seasonal pattern and this indicate that H. nemurus is a non-seasonal breeder with several spawning cycles and can be referred to as indeterminate batch spawner. The major significances of this study are annual sex steroid hormonal profile and asynchronous ovarian development of H. nemurus. This information will contribute to our knowledge of reproductive biology of H. nemurus.

Exposure to bisphenol A modulates hormone concentrations in Gammarus pseudolimnaeus

Bisphenol A (BPA) is an endocrine-disrupting compound that can enter aquatic systems through landfill leachate or wastewater effluent. Although impacts of BPA on vertebrates are well documented, its effects on invertebrates are less clear. Amphipods such as Gammarus pseudolimnaeus Bousfield, 1958 are often prevalent invertebrates in freshwater ecosystems and can provide a powerful invertebrate model system to investigate the endocrine-disruptive capabilities of BPA. However, techniques to assay hormone concentrations in amphipods, especially vertebrate-like steroid sex hormones, are not widespread. In this study, we (i) quantified estrogen concentrations in juveniles and in adult female amphipods; (ii) quantified testosterone concentrations in juveniles and in adult male amphipods; and (iii) delineated changes to estrogen and testosterone concentrations of adults and juveniles following a 9-day exposure to BPA at four levels: 0 (control), 10, 50, and 100 µg/L BPA. Tissue extracts from homogenized samples were analyzed for estrogen or testosterone concentrations via radioimmunoassay for each reproductive class of amphipod. Low concentrations of BPA significantly increased estrogen concentrations in adult females and in juveniles. Moderate and high concentrations of BPA significantly increased testosterone concentrations in adult males, and low and moderate concentrations of BPA significantly increased testosterone concentrations of juveniles.

Fate of endogenous steroid hormones in steer feedlots under simulated rainfall-induced runoff

Steroid hormones pose potential risks to fish and other aquatic organisms at extremely low concentrations. To assess the factors affecting the release of endogenous estrogenic and androgenic steroids from feedlots during rainfall, runoff, and soil samples were collected after simulated rainfall on a 14-steer feedlot under different rainfall rates and aging periods and analyzed for six steroid hormones. While only 17α-estradiol, testosterone, and progesterone were detected in fresh manure, 17β-estradiol, estrone, and androstenedione were present in the surficial soil after two weeks. In the feedlot surficial soil, concentrations of 17α-estradiol decreased by approximately 25% accompanied by an equivalent increase in estrone and 17β-estradiol. Aging of the feedlot soils for an additional 7 days had no effect on estrogen and testosterone concentrations, but androstenedione concentrations decreased substantially, and progesterone concentrations increased. Androstenedione and progesterone concentrations in the surficial soil were much higher than could be accounted for by excretion or conversion from testosterone, suggesting that other potential precursors, such as sterols, were converted after excretion. The concentration of androgens and progesterone in the soil were approximately 85% lower after simulated rainfall, but the estrogen concentrations remained approximately constant. The decreased masses could not be accounted for by runoff, suggesting the possibility of rapid microbial transformation upon wetting. All six steroids in the runoff, with the exception of 17β-estradiol, were detected in both the filtered and particle-associated phases at concentrations well above thresholds for biological responses. Runoff from the aged plots contained less 17α-estradiol and testosterone, but more estrone, androstenedione, and progesterone relative to the runoff from the unaged plots, and most of the steroids had a lower particle-associated fraction.

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.