Development of an anti-vitellin ELISA for the assessment of reproduction in the ridgeback shrimp, Sicyonia ingentis

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.

Induction of vitellogenesis, methyl farnesoate synthesis and ecdysteroidogenesis in two edible crabs by arachidonic acid and prostaglandins

The present study investigated the effect of arachidonic acid (AA) and selected prostaglandins on the regulation of vitellogenesis, ecdysteroidogenesis and methyl farnesoate (MF) synthesis in the freshwater crab Oziotelphusa senex senex and the giant mud crab, Scylla serrata Administration of AA and prostaglandin F_2α (PGF_2α) and prostaglandin E₂ (PGE₂) significantly increased ovarian index, oocyte diameter and ovarian vitellogenin levels and ecdysteroid and MF levels in the hemolymph of crabs. Secretions of MF and ecdysteroids from in vitro cultured mandibular organs (MO) and Y-organs (YO) isolated from intermolt crabs injected with AA, PGF_2α and PGE₂ were greater when compared with controls. In contrast, injection of prostaglandin D₂ (PGD₂) had no effect on vitellogenesis, ecdysteroid and MF levels in circulation. In vitro secretion of MF from MO explants isolated from avitellogenic crabs incubated with AA, PGF_2α and PGE₂ increased in a time-dependent manner. Conversely, incubation of YOs isolated from avitellogenic crabs with AA, PGF_2α and PGE₂ had no effect on secretion of ecdsyteroids. These results implicate prostaglandins in the regulation of reproduction by inducing the synthesis of MF and consequent ecdysteroid synthesis in brachyuran crabs, and provide an alternative molecular intervention mechanism to the traditional eyestalk ablation methodology to induce vitellogenesis and ovarian maturation in crustaceans.

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.

Bioaccumulation of TBT and Its Cellular Toxic Effects on the Freshwater Prawn Macrobrachium rosenbergii

To test the toxic effects of tributyltin (TBT), Macrobrachium rosenbergii were exposed to three concentrations of TBT viz. 10 ng/L, 100 ng/L and 1000 ng/L for 90 days. The bioaccumulation of TBT level varied in hepatopancreas based upon dose dependent manner. Histopathological results revealed the reduction in basement membrane thickness, disruption of the hepatopancreatic tubules and abnormal lumen in hepatopancreas of TBT treated prawns. The ultrastructure of the control prawn showed normal architecture of cellular organelles with prominent nuclei in hepatocytes. On the other hand, many vacuoles, irregular arrangements of microvilli, swollen mitochondria, distorted rough endoplasmic reticulum cisternaes and abnormal nucleus were seen in the TBT treated group. Further, the biochemical and vitellogenin content were altered remarkably due to TBT exposure. It directly indicated that TBT had conspicuously inhibited the vitellogenesis. Therefore, it was inferred that the administration of TBT has considerably affected the hepatopancreatic functions in M. rosenbergii.

Controversial use of vitellogenin as a biomarker of endocrine disruption in crustaceans: New adverse pieces of evidence in the copepod Eurytemora affinis

In recent years, the interest in the use of vitellogenin (VTG) as a biomarker of endocrine disruption in fish has led to VTG being considered as a potential tool in invertebrates. Among aquatic invertebrate models in ecotoxicology, the copepods are considered as reference species in marine, estuarine and freshwater ecosystems. In this context, we identified a VTG cDNA in Eurytemora affinis. The Ea-VTG2 cDNA is 5416bp in length with an open reading frame (ORF) of 5310bp that encodes a putative protein of 1769 amino acids residues. Phylogenetic analysis confirmed the hypothesis of a VTG duplication event before the emergence of the copepod species. The analysis of the Ea-VTG2 expression by qPCR in males and females according to their reproductive stages allowed transcript basal levels to be determined. The expression pattern revealed a gradual increase of transcript levels during maturation in females. Important inter-sex differences were observed with a VTG level in males ranging from about 1900- to 6800-fold lower than in females depending on their stage. Moreover, the protein was only detected in ovigerous females. The inducibility of Ea-VTG2 by chemicals was studied in males exposed to either a model of endocrine disruptor in vertebrates i.e. 4-nonylphenol (4-NP) or a crustacean hormone i.e. Methyl Farnesoate (MF), and in males sampled from a multi-contaminated estuary. No induction was highlighted. The VTG should not be considered as an appropriate biomarker in E. affinis as previously suggested for other crustaceans.

Molecular cloning and expression of the vitellogenin gene and its correlation with ovarian development in an invasive pest Octodonta nipae on two host plants

There is an ongoing relationship between host plants and herbivores. The nutrient substances and secondary compounds found in the host plant can not only impact the growth and development process of herbivores, but, more importantly, may also affect their survival and reproductive fitness. Vitellogenesis is the core process of reproductive regulation and is generally considered as a reliable indicator for evaluating the degree of ovarian development in females. Vitellogenin (Vg) plays a critical role in the synthesis and secretion of yolk protein. In this study, the full-length cDNA of the Vg gene in an alien invasive species, the nipa palm hispid beetle Octodonta nipae Maulik (Coleoptera: Chrysomelidae) (OnVg) was cloned and, the effect of host plant on the OnVg expression level and ovarian development was investigated. The results revealed that the OnVg was highly and exclusively expressed in adult females, but barely detectable in larvae, pupae and adult males. The relative expression level of OnVg and egg hatchability were much higher in females fed on Phoenix canariensis (their preferred host) than those fed on Phoenix roebelenii. A positive correlation relationship between OnVg expression and egg hatchability was also detected. Additionally, the anatomy of the female reproductive system showed that the ovaries of individuals fed on P. canariensis were considerably more developed than in females fed on P. roebelenii. The results may be applicable to many pest management situations through reproductive disturbance by alternating host plant species or varieties or by reproductive regulation through vitellogenesis mediated by specific endocrine hormones.

Effect of 17α-hydroxyprogesterone and 17α-hydroxypregnenolone on sperm quality and sperm quantity in male mud spiny lobster (Panulirus polyphagus)

The present study aimed to determine the effect of 17α-hydroxyprogesterone (17α-OHP) and 17α-hydroxypregnenolone (17α-OHPL) on sperm quality and sperm quantity in male mud spiny lobster (Panulirus polyphagus). The mean of sperm quality was increased in 17α-OHP and 17α-OHPL treated hormones. In 17α-OHP injected animals, the mean of sperm quantity of dose 0.01 μg g(-1) b.wt. was increased than 17α-OHPL. Meanwhile, 17α-OHP and 17α-OHPL concentrations were lower when injected with the hormones but 17α-OHP was higher at only day 15 (dose 0.01 and 0.1 μg g(-1) b.wt.). For 17α-OHPL, the hormone was a prohormone in the body of P. polyphagus and only required smaller to increase the sperm quantity. Besides, when the higher dose of 17α-OHPL (0.1 μg g(-1) b.wt.) was used in P. polyphagus, the development of P. polyphagus was inhibited and decreased the sperm quantity and 17α-OHPL concentration in hemolymph was lower. Injection of 17α-OHP in P. polyphagus has increased the sperm quality and quantity for both 17α-OHP dosage of 0.01 and 0.1 μg g(-1) b.wt. However, injection of 17α-OHPL in P. polyphagus has decreased the sperm quantity only, also for both dosage of 0.01 and 0.1 μg g(-1) b.wt. and lower on hormone concentration.

TBT effects on the development of intersex (ovotestis) in female fresh water prawn Macrobrachium rosenbergii

The impact of tributyltin (TBT) on the female gonad and the endocrine system in Macrobrachium rosenbergii was studied. Prawns were exposed to environmentally realistic concentrations of 10, 100, and 1000 ng/L of TBT for 6 months. Dose dependent effects were noticed in TBT exposed prawns. At 1000 ng/L TBT caused ovotestis formation (formation of male germ cells in ovary). Presence immature oocytes, fusion of developing oocytes, increase in interstitial connective tissues, and its modification into tubular like structure and abundance of spermatogonia in the ovary of TBT treated prawns. The control prawn ovary showed normal architecture of cellular organelles such as mature oocytes with type 2 yolk globules, lipid droplets, normal appearance of yolk envelop, and uniformly arranged microvilli. On the other hand, type 1 yolk globules, reduced size of microvilli, spermatogonial cells in ovary, spermatogonia with centrally located nucleus, and chromatin distribution throughout the nucleoplasm were present in the TBT treated group. Immunofluorescence staining indicated a reduction in vitellin content in ovary of TBT treated prawn. Moreover, TBT had inhibited the vitellogenesis by causing hormonal imbalance in M. rosenbergii. Thus, the present investigation demonstrates that TBT substantially affects sexual differentiation and gonadal development in M. rosenbergii.

Effect of testosterone undecanoate hormone on sperm and its level in the hemolymph of male mud spiny lobster, Panulirus polyphagus

The present study aimed to determine the effect of testosterone undecanoate hormone on sperm quality (sperm viability) and sperm quantity (sperm counts) and its levels in the hemolymph of male mud spiny lobster, Panulirus polyphagus. Male P. polyphagus was injected laterally in fifth abdominal segment of pure hormone, Testosterone Undecanoate (TU) and ethanol at days 1, 8, 15, 22 and 29. Hemolymph of P. polyphagus was taken every two weeks and checked with Enzyme-linked immunosorbent assay (ELISA) to measure hormone levels. The mean sperm quality and quantity were increased due to increase the TU dose and TU levels also increase. The sperm quality, quantity and hormone levels were relevance each others. These findings indicate that TU injection should be evaluated as a practical way of improving sperm quality and quantity in commercial operations.

Impact of TBT on the vitellogenesis and sex hormones in freshwater prawn Macrobrachium rosenbergii (De Man, 1879)

BACKGROUND

Tributyltin (TBT) is a ubiquitous persistent xenobiotic that can be found in freshwater, estuarine and marine ecosystem. TBT is a strong endocrine disrupting compound (EDC) that can cause toxic threat to aquatic organisms. Imposex, sexual deformities and endocrine dysfunctions are the causes of TBT to most of the aquatic organisms. Effect of TBT on the vitellogenesis and sex hormonal changes in Macrobrachium rosenbergii has never been reported. Hence, the present investigation was undertaken to find out the impact of TBT on histological changes in the different reproductive tissues, sex hormonal alterations and level of biomarkers like vitellogenin and vitellin in M. rosenbergii.

RESULTS

The present investigation documents the possible impact of tributyltin (TBT) on the vitellogenesis in freshwater female prawn M. rosenbergii. TBT at 10 ng/l, 100 ng/l and 1000 ng/l concentrations were exposed individually to prawns for a period of three months. At higher concentration of 1000 ng/l, the ovarian development was arrested and ovary remained at spent stage. At lower concentration of TBT (10 ng/l), the development proceeded up to early vitellogenic stage. At intermediate concentration of 100 ng/l TBT, the ovary remained at pre vitellogenic stage and thereafter no development was noticed. Histological results indicated the normal ovarian development with vitellogenic oocytes, filled with yolk globules in control prawn. On the other hand, the TBT treated groups showed reduction in yolk globules, fusion of developing oocytes and abundance of immature oocytes. Immunofluorescence staining denoted the remarkable reduction in vitellin content in ovary of TBT treated prawn. Hence, TBT had conspicuously inhibited the vitellogenesis by causing hormonal imbalance in M. rosenbergii.

CONCLUSION

TBT had notably inhibited the vitellogenesis due to hormonal imbalance. This endocrine dysfunction ultimately impaired the oogenesis in the freshwater female prawn M. rosenbergii.

Vitellogenin and lipovitellin from the prawn Macrobrachium borellii as hydrocarbon pollution biomarker

During reproduction vitellogenin (VTG) is transported to vitellogenic oocytes as a precursor of egg yolk lipovitellin (LV). As VTG synthesis is affected by environmental stressors, it is widely used as biomarker in endocrine disruption studies. However, it has seldom been employed to evaluate invertebrate hydrocarbon pollution. An ELISA with anti-LV antibody was developed to evaluate the impact of water-soluble fraction of crude oil (WSF) on Macrobrachium borellii vitellogenesis. Prawn VTG concentration was within the range reported for other crustaceans; LV values were positively correlated with gonadosomatic index (GSI). Females at different vitellogenic stages were exposed to a sub-lethal concentration of WSF for 7 days. Exposed animals with GSI>7 increased their VTG and LV titer as compared to control organisms (190% and 140%, respectively). VTG levels in M. borellii were upregulated and highly sensitive to WSF exposure. This assay could be employed as a biomarker for freshwater hydrocarbon pollution.

Immunolocalization of estrogen receptor α in Neomysis japonica oocytes and follicle cells during ovarian development

Estrogen induces oocytes development and vitellogenesis in crustacean by interacting with estrogen receptor (ER) subtypes. In the present study, we detect for the first time the ERα in oocytes and follicle cells and hepatopancreas cells of mysis by immunohistochemistry using a specific ERα antibody. ERα was mainly localized in the nuclei of oocytes and follicle cells, while mainly detected in nuclei of oogonia (OG), previtellogenic oocyte (PR) and endogenous vitellogenic oocyte (EN) at previtellogenic and early vitellogenic stage (I-early III). Follicle cells in all stages of ovary (all vitellogenic stages) showed strong ERα positive reaction, and they were able to gradually move to oocytes during the development of oocytes. In addition, ERα was also localized in the nuclei and cytoplasm of four hepatopancreas cells (including E-, R-, F- and B-cell) in all ovary stages. These findings suggest, for the first time to our knowledge, that there could be a close link between oogenesis, follicle cells, hepatopancreas cells and endocrine regulation, and estrogens might be involved in the regulation of oocytes at early ovarian stage in mysis.

Effects of 17 beta-estradiol on the vitellogenin synthesis and oocyte development in the ovary of kuruma prawn (Marsupenaeus japonicus)

The effects of 17 beta-estradiol on induction of vitellogenin synthesis and oocyte development were investigated in previtellogenic ovary of immature kuruma prawn (Marsupenaeus japonicus) incubated with Medium 199. After three days incubation of previtellogenic ovary, Vg concentrations in media containing 3.6 nM, 36.7 nM, 367 nm and 3671 nM 17 beta-estradiol were significantly (p<0.01) greater than that of Ringer solution or the pure ethanol vehicle. Furthermore, a more advanced stage of oocyte development at oil globule stage (primary vitellogenic stage), which is surrounded by round and greatly expanded follicle cells, was observed in previtellogenic ovarian pieces incubated in media containing 3.6, 36.7, 367 and 3671 nM 17 beta-estradiol. The results of these studies show that 17 beta-estradiol induces Vg synthesis and appearance of primary vitellogenic oocyte in the ovary of immature prawns.

Characterization of vitellin from the ovaries of the banana shrimp Litopenaeus merguiensis

Vitellin (Vt) was purified from ovary extracts of mature females of the banana shrimp Litopenaeus merguiensis using DEAE-Sephacel and Superdex 200 columns. Native Vt had an apparent molecular mass of 398 kDa as determined by native PAGE and by gel filtration chromatography. Under reducing and denaturing conditions (SDS-PAGE), Vt is composed of two major subunits of 87 and 78 kDa, although some faint bands were also detected. The N-terminal 10 amino acids sequence of the 78 kDa subunit is identical to that of Litopenaeus vannamei Vt and very similar to that of Litopenaeus japonicus vitellogenin (Vg) as well as Litopenaeus semisulcatus Vt, with an identity of 89%. Anti-Vt polyclonal antibody raised against purified Vt shows a high specificity with only ovarian Vt and hemolymph Vg of vitellogenic shrimps in double immunodiffusion and Western blot assays. Vg and Vt concentrations in hemolymph, hepatopancreas and ovaries were measured by ELISA. Vg concentrations increased in the hemolymph in the early stages of ovarian development and declined in the maturation stages. As there were undetectable concentrations of Vg in the hepatopancreas while an elevation of Vg levels occurred in the hemolymph, during the time that Vt was accumulating in the ovaries during oogenesis, this would suggest that the contribution of Vg synthesized by the hepatopancreas only might be not sufficient for adequate development of the oocytes in the banana shrimp L. merguiensis during vitellogenesis.

Development of a quantitative enzyme-linked immunosorbent assay for vitellin in the mysid Neomysis integer (Crustacea: Mysidacea)

Mysid crustaceans have been put forward by several regulatory bodies as suitable test organisms to screen and test the potential effects of environmental endocrine disruptors. Despite the well-established use of mysid reproductive endpoints such as fecundity, egg development time, and time to first brood release in standard toxicity testing, little information exists on the hormonal regulation of these processes. Control of vitellogenesis is being studied intensively because yolk is an excellent model for studying mechanisms of hormonal control, and vitellogenesis can be chemically disrupted. Yolk protein or vitellin is a major source of nourishment during embryonic development of ovigorous egg-laying invertebrates. The accumulation of vitellin during oocyte development is vital for the production of viable offspring. In this context, we developed a competitive enzyme-linked immunosorbent assay (ELISA) for vitellin of the estuarine mysid Neomysis integer. Mysid vitellin was isolated using gel filtration, and the purified vitellin was used to raise polyclonal antibodies. The ELISA was sensitive within a working range of 4 to 500 ng vitellin/mL. Serial dilutions of whole body homogenates from female N. integer and the vitellin standard showed parallel binding curves, validating the specificity of the ELISA. The intra- and interassay coefficients of variation were 8.2% and 13.8%, respectively. Mysid vitellin concentrations were determined from ovigorous females and eggs at different developmental stages. The availability of a quantitative mysid vitellin ELISA should stimulate further studies on the basic biology of this process in mysids. Furthermore, it could provide a means to better understand and predict chemically induced reproductive effects in mysids.

Purification and characterization of vitellin from the estuarine mysid Neomysis integer (Crustacea; Mysidacea)

Invertebrates account for roughly 95% of all animals, yet surprisingly, little effort has been invested to understand their value in signaling potential environmental endocrine disruption. There has been, however, much recent attention on vitellogenin induction in egg-laying invertebrates and vertebrates as indicators of exposure to estrogenic xenobiotics. Mysid shrimp (Crustacea: Mysidacea) have been put forward by several researchers and regulatory bodies (e.g., US-EPA) as suitable test organisms for the evaluation of environmental endocrine disruption. In view of developing sensitive assays to study endocrine disruption in the estuarine mysid Neomysis integer, we isolated and characterized vitellin, the major yolk protein in eggs. Vitellin was purified using gel filtration and characterized by electrophoresis using different staining procedures. Specific (as shown by Western blotting) polyclonal antibodies were produced in rabbit against the purified vitellin of N. integer. These antisera will be used to develop immunoassays to study vitellogenesis in mysids and to detect potential stimulatory or inhibitory effects of endocrine disruptors on the production of vitellin.

Purification of vitellin from the ovary of Chinese mitten-handed crab (Eriocheir sinensis) and development of an antivitellin ELISA

Vitellin was purified from ovaries of mature female Chinese mitten-handed crab (Eriocheir sinensis) using gel filtration chromatography. Analysis by native PAGE showed the vitellin had a native molecular mass of 520 kDa, while denaturing SDS-PAGE revealed two subunits of 97 and 74 kDa. Purified vitellin was used to raise polyclonal antisera, with which an enzyme-linked immunosorbent assay (ELISA) was developed. The ELISA was sensitive and could effectively detect vitellin in the range of 7.8-500 ng. Furthermore, vitellin levels in various developmental stages of oogenesis were measured with the ELISA assay. The results indicated that levels of vitellin increased significantly from 0.22 mg/ovary at Stage II to 360.31 mg/ovary at Stage IV.