The role of hormones in the acquisition of sperm motility in salmonid fish

Disruptive effects of genistein and daidzein on steroidogenesis, testicular development and maturation of Cyprinus carpio (Linn, 1758) males

A 60-day feeding trial was conducted to evaluate the combined effect of dietary soy phytoestrogens, specifically genistein and daidzein, on the gonadal recrudescence and maturation of male Cyprinus carpio (Linnaeus, 1758). Adult male C. carpio (60 ± 10 g) were fed with a diet with no added genistein or daidzein (C), 110 mg/100 mg genistein (GL), 210 mg/100 g genistein (GH), 4 mg/100 g daidzein (DL), 8 mg/100 g daidzein (DH), combination of 110 mg/100 mg genistein and 4 mg/100 g daidzein (DGL, equivalent to 17.5% soybean meal) and combination of 210 mg/100 g genistein and 8 mg/100 g daidzein (DGH, equivalent to 35% soybean meal) for 60 days. The fish were spent by injection of the inducing agent before the experiment to maintain the homogeneity in maturity stages. Serum 11-ketotestosterone and 17β-estradiol levels increased substantially (p < 0.05), while serum cortisol and 17α,20β dihydroxy progesterone levels were significantly (p < 0.05) lower in GH, DH, DL, DGL and DGH groups. The gene expression of cyp19a1a and 20β-HSD were significantly downregulated (p < 0.05) in GH, DH, and DGH. The ratio of spermatozoa to spermatocytes was lower in high doses of phytoestrogens and their combination treatments (GH, DH and DGH) than in the lower dose fed groups. The GSI (gonad somatic index) values showed a dose-dependent increase in the isoflavone-fed groups. Hence, the study concluded that the feeding of diets with a combination of 210 mg/100 g genistein and 8 mg/100 g daidzein (DGH), which is equivalent to 35% of soybean meal in the diet, disrupted the sex steroid profile and steroidogenic enzymes expression and caused a delay in maturation in the male common carp. Thus, soybean meal can be included in the diet of male common carp broodstock at levels up to 17.5%. However, inclusion levels above 35% have been shown to impair normal reproductive function.

Human and fish differences in steroid receptors activation: A review

Steroid receptors (SRs) are transcription factors activated by steroid hormones (SHs) that belong to the nuclear receptors (NRs) superfamily. Several studies have shown that SRs are targets of endocrine disrupting chemicals (EDCs), widespread substances in the environment capable of interfering with the endogenous hormonal pathways and causing adverse health effects in living organisms and/or their progeny. Cell lines with SRs reporter gene are currently used for in vitro screening of large quantities of chemicals with suspected endocrine-disrupting activities. However, most of these cell lines express human SRs and therefore the toxicological data obtained are also extrapolated to non-mammalian species. In parallel, in vivo tests have recently been developed on fish species whose data are also extrapolated to mammalian species. As some species-specific differences in SRs activation by natural and synthetic chemicals have been recently reported, the aim of this review is to summarize those between human and fish SRs, as representatives of mammalian and non-mammalian toxicology, respectively. Overall, this literature study aims to improve inter-species extrapolation of toxicological data on EDCs and to understand which reporter gene cell lines expressing human SRs are relevant for the assessment of effects in fish and whether in vivo tests on fish can be properly used in the assessment of adverse effects on human health.

Deleterious effect of gestagens from wastewater effluent on fish reproduction in aquatic environment: A review

Gestagens are common pollutants accumulated in the aquatic ecosystem. Gestagens are comprised of natural gestagens (i.e. progesterone) and synthetic gestagens (i.e. progestins). The major contributors of gestagens in the environment are paper plant mill effluent, wastewater treatment plants, discharge from pharmaceutical manufacturing, and livestock farming. Gestagens present in the aquatic environment interact with progesterone receptors and other steroid hormone receptors, negatively influencing fish reproduction, development, and behavior. In fish, the gonadotropin induces 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) production, an important steroid hormone involved in gametogenesis. DHP interacts with the membrane progestin receptor (mPR), which regulates sperm motility and oocyte maturation. Gestagens also interfere with the hypothalamic-pituitary-gonadal (HPG) axis, which results in altered hormone levels in fish. Moreover, recent studies showed that even at low concentrations exposure to gestagens can have detrimental effects on fish reproduction, including reduced egg production, masculinization, feminization in males, and altered sex ratio, raising concerns about their impact on the fish population. This review highlights the hormonal regulation of sperm motility, oocyte maturation, the concentration of environmental gestagens in the aquatic environment, and their detrimental effects on fish reproduction. However, the long-term and combined impacts of multiple gestagens, including their interactions with other pollutants on fish populations and ecosystems are not well understood. The lack of standardized regulations and monitoring protocols for gestagens pollution in wastewater effluent hampers effective control and management. Nonetheless, advancements in analytical techniques and biomonitoring methods provide potential solutions by enabling better detection and quantification of gestagens in aquatic ecosystems.

Seasonal and age-related changes in sperm quality of farmed arctic charr (Salvelinus alpinus)

BACKGROUND

Substantial variation in male fertility is regularly observed in farmed Arctic charr. However, detailed investigations of its fluctuation during a reproductive season and across years are lacking. Furthermore, information about the effect of underlying genetic factors influencing sperm quality is scarce. The current study focused on seasonal and age-related factors that may affect sperm quality characteristics in males reared in natural and delayed photoperiods. Animals were sampled three times for two consecutive years, and sperm quality parameters were recorded using a computer-assisted sperm analysis (CASA) system. Thereafter, high-throughput sequencing technologies were applied, aiming to identify genomic regions related to the variation of sperm quality throughout the reproductive season.

RESULTS

An across-season variation in the recorded sperm quality parameters was evident. Overall, 29% and 42% of males from the natural and delayed spawning groups had a highly variable total progressive motility. Males at four years of age showed significantly higher sperm motility and velocities during the early October and November recordings compared to the following year when the same animals were five years of age. On the other hand, the opposite was observed regarding sperm concentration during the last sampling. A genome-wide FST scan detected SNP differentiation among males with high and low variability in total progressive motility (PM) on eight chromosomes (FST > 0.17), Genome wide windows with the highest FST contained SNPs in proximity (within 250 kb up- and downstream distance) to 16 genes with sperm quality biological functions in mammalian species.

CONCLUSION

Our findings provide a detailed view of seasonal, age-related, and genetic effects on sperm quality and can be used to guide decisions on broodstock selection and hatchery management.

A progestin regulates the prostaglandin pathway in the neuroendocrine system in female mudskipper Boleophthalmus pectinirostris

Sex hormones regulate the reproductive cycle through brain-pituitary axis, but the molecular mechanism is still enigmatic. In the reproductive season, the mudskipper Boleophthalmus pectinirostris possesses a semilunar periodicity spawning rhythm, which coincides with the semilunar periodicity variations in 17α-hydroxyprogesterone, the precursor of 17α,20β-dihydroxy-4-pregnen-3-one (DHP), a sexual progestin in teleosts. In the present study, we investigated in vitro the brain transcriptional differences between DHP-treated tissues and control groups using RNA-seq. Differential expression analysis revealed that 2700 genes significantly differentially expressed, including 1532 up-regulated and 1168 down-regulated genes. The majority of prostaglandin pathway-related genes were dramatically up-regulated, especially the prostaglandin receptor 6 (ptger6). Tissue distribution analysis revealed that ptger6 gene was ubiquitously expressed. In situ hybridization results showed that ptger6, nuclear progestin receptor (pgr), and DHP-induced c-fos mRNA were co-expressed in the ventral telencephalic area, the ventral nucleus of ventral telencephalic area, the anterior part of parvocellular preoptic nucleus, the magnocellular part of magnocellular preoptic nucleus, the ventral zone of periventricular hypothalamus, the anterior tubercular nucleus, the periventricular nucleus of posterior tuberculum, and the torus longitudinalis. DHP significantly enhanced promoter activities of ptger6 via Pgr. Together, this study suggested that DHP regulates the prostaglandin pathway in the neuroendocrine system of teleost fish.

Sex steroid profile during oocyte development and maturation in the intertidal worm Marphysa madrasi (Polychaeta: Eunicidae) from the east coast of India

Marphysa madrasi is a commercially valuable maturation diet in crustacean aquaculture. This study presents the first detailed investigation of oogenesis in the intertidal polychaete worm M. madrasi and reports the steroid profile during oocyte growth and development. Oogenesis is extraovarian type I, originating from coelomic epithelial cells, with four stages of development - primary growth, early vitellogenic, late vitellogenic, and maturation. The primary growth phase contains oogonial cells and previtellogenic oocyte clusters in the early, mid, and late stages of development form a dispersed ovary attached to blood vessels. The late previtellogenic oocytes detach from the ovary at the onset of vitellogenesis. The detached oocytes complete vitellogenesis and final maturation in the coelomic fluid as solitary free-floating cells without any connection with follicle cells. The worms display asynchronous reproduction with a heterogeneous population of developing oocytes. Steroid extracts from the polychaete homogenates in different stages of oogenesis were identified by HPLC and confirmed by LC-MS/MS. In M. madrasi, two vertebrate-type steroids, pregnenolone (P5) and 17α-hydroxyprogesterone (17-OHP) were detected and quantified. The P5 levels were low in immature worms but increased significantly by ∼ 8.3-fold in the previtellogenic stage and peaked during oocyte maturation. 17-OHP levels were low in immature worms but gradually increase as the oogenesis progress to the primary growth and early vitellogenic phase, with a significant increase (p < 0.001) during the late vitellogenic phase. Although an increase in the concentration of P5 and 17-OHP during vitellogenesis and maturation of oocytes points to a possible role in reproduction, the absence of other vertebrate-type steroids in the investigated polychaete signifies a plausible uptake of P5 and 17-OHP from the environment.

Tenets in Microbial Endocrinology: A New Vista in Teleost Reproduction

Climate vulnerability and induced changes in physico-chemical properties of aquatic environment can bring impairment in metabolism, physiology and reproduction in teleost. Variation in environmental stimuli mainly acts on reproduction by interfering with steroidogenesis, gametogenesis and embryogenesis. The control on reproductive function in captivity is essential for the sustainability of aquaculture production. There are more than 3,000 teleost species across the globe having commercial importance; however, adequate quality and quantity of seed production have been the biggest bottleneck. Probiotics are widely used in aquaculture as a growth promoter, stress tolerance, pathogen inhibition, nutrient digestibility and metabolism, reproductive performance and gamete quality. As the gut microbiota exerts various effects on the intestinal milieu which influences distant organs and pathways, therefore it is considered to be a full-fledged endocrine organ. Researches on Gut-Brain-Gonad axis (GBG axis) and its importance on physiology and reproduction have already been highlighted for higher mammals; however, the study on fish physiology and reproduction is limited. While looking into the paucity of information, we have attempted to review the present status of microbiome and its interaction between the brain and gut. This review will address a process of the microbiome physiological mechanism involved in fish reproduction. The gut microbiota influences the BPG axis through a wide variety of compounds, including neuropeptides, neurotransmitter homologs and transmitters. Currently, research is being conducted to determine the precise process by which gut microbial composition influences brain function in fish. The gut-brain bidirectional interaction can influence brain biochemistry such as GABA, serotonin and tryptophan metabolites which play significant roles in CNS regulation. This review summarizes the fact, how microbes from gut, skin and other parts of the body influence fish reproduction through the Gut-Brain-Gonad axis.

A chronic exposure to bisphenol A reduces sperm quality in goldfish associated with increases in kiss2, gpr54, and gnrh3 mRNA and circulatory LH levels at environmentally relevant concentrations

The bisphenol A (BPA)-disrupted reproductive functions have been demonstrated in male animals. In fish, it has been shown that environmentally relevant concentrations of BPA decrease sperm quality associated with inhibition of androgen biosynthesis. However, BPA effects on neuroendocrine regulation of reproduction to affect testicular functions are largely unknown. In the present study, reproductive functions of hypothalamus and pituitary were studied in mature male goldfish exposed to nominal 0.2, 2.0 and 20.0 μg/L BPA. At 90 d of exposure, sperm volume, velocity, and density and motility were decreased in goldfish exposed to 0.2, 2.0, and 20.0 μg/L BPA, respectively (p < 0.05). At 30 d of exposure, there were no significant changes in circulatory LH levels and mRNA transcripts of kiss1, Kiss2, gpr54, and gnrh3. At 90 d of exposure, circulatory LH levels showed trends toward increases in BPA exposed goldfish, which was significant in those exposed to 2.0 μg/L (P < 0.05). At this time, Kiss2, gpr54, and gnrh3 mRNA levels were increased in goldfish exposed to any concentrations of BPA (p < 0.05). This study shows that BPA-diminished sperm quality was accompanied by an increase in circulatory LH levels associated with increases in mRNA transcripts of upstream neuroendocrine regulators of reproduction in goldfish. Further, this is the first study to report circulatory levels of LH in fish exposed to BPA.

The Effect of Hormonal Treatment on Selected Sperm Quality Parameters and Sex Steroids in Tropical Cyprinid Bala Shark Balantiocheilos melanopterus

Hormone treatments are routinely employed with bala shark Balantiocheilos melanopterus male broodstock to stimulate the production of high-quality sperm. In the current trial, three spermiation-inducing treatments were evaluated: 20 μg/kg body weight (BW) recombinant hCG; 20 μg/kg BW [D-Ala6, Pro9, NEt]- gonadotropin-releasing hormone (GnRHa) with 20 mg/kg BW metoclopramide; and poly(lactic-co-glycolic acid) (PLGA) microparticles with slow release of 10 μg/kg BW GnRHa. A 0.9% saline AS negative control was also included. Administration of the GnRHa through the form of slow release of PLGA microparticles 24 h after treatment resulted in a significantly higher sperm volume, motility percentage, and total sperm count compared to the control. Injection of GnRHa with metoclopramide induced sperm parameters that did not differ from the control, with the exception of motility percentage. The lowest potency to induce spermiation in bala sharks was in the treatment with recombinant hCG. Both PLGA microparticles and GnRHa with metoclopramide significantly increased blood plasma concentrations of testosterone and 11-ketotestosterone compared to the control. The PLGA microparticle system with continuous release of 10 μg/kg BW GnRHa was the most effective treatment in inducing spermiation in bala sharks.

The Comparative Survey of Coordinated Regulation of Steroidogenic Pathway in Japanese Flounder (Paralichthys olivaceus) and Chinese Tongue Sole (Cynoglossus semilaevis)

Steroidogenesis controls the conversion of cholesterol into steroid hormones through the complex cascade reaction of various enzymes, which play essential roles in sexual differentiation and gonadal development in vertebrates, including teleosts. Japanese flounder (Paralichthys olivaceus) and Chinese tongue sole (Cynoglossus semilaevis) are important marine cultured fishes in China and have remarkable sexual dimorphism with bigger females and sex reversal scenarios from female to neo-male. Several steroidogenic genes have been analyzed individually in the two species, but there is a lack of information on the coordinated interaction of steroidogenic gene regulation. Therefore, in this study, through genomic and transcriptomic analysis, 39 and 42 steroidogenic genes were systematically characterized in P. olivaceus and C. semilaevis genomes, respectively. Phylogenetic and synteny analysis suggested a teleost specific genome duplication origin for cyp19a1a/cyp19a1b, hsd17b12a/hsd17b12b, ara/arb and esr2a/esr2b but not for star/star2 and cyp17a1/cyp17a2. Comparative transcriptome analysis revealed conserved expression patterns for steroidogenic genes in P. olivaceus and C. smilaevis gonads; star/star2, cyp11a/cyp11c, cyp17a1/cyp17a2, cyp21a, hsd3b1, hsd11b and hsd20b were strongly expressed in testis, while cyp19a1a and hsd17b genes were highly expressed in ovaries. Only a few genes were differentially expressed between male and neo-male testis of both P. olivaceus and C. semilaevis, and even fewer genes were differentially regulated in the brains of both species. Network analysis indicated that cyp11c, cyp17a1 and hsd3b1 actively interacted with other steroidogenic genes in P. olivaceus and C. semilaevis, and may play a more sophisticated role in the steroid hormone biosynthesis cascade. The coordinated interaction of steroidogenic genes provided comprehensive insights into steroidogenic pathway regulation with a global biological impact, as well as sexual development in teleost species.

Hdh-Tektin-4 Regulates Motility of Fresh and Cryopreserved Sperm in Pacific Abalone, Haliotis discus hannai

As structural components of sperm, tektins are thought to play a fundamental role in sperm flagellar motility. In this study, Tektin-4 (Hdh-TEKT4) gene was successfully cloned and characterized from the testis tissue in Pacific abalone, Haliotis discus hannai. The full-length cDNA of Hdh-TEKT4 was 1,983 bp, with a coding region of 1,350 bp encoding 51.83 kDa putative protein of 449 deduced amino acids. Hdh-TEKT4 contains a tektin domain including a nonapeptide signature motif (RPGVDLCRD). Fluorescence in situ hybridization revealed that Hdh-TEKT4 localized in the spermatids of Pacific abalone testis. qRT-PCR analysis showed that Hdh-TEKT4 was predominantly expressed in testis tissues. Hdh-TEKT4 mRNA expression was upregulated during the fully mature testicular developmental stage in both seasonal development and EAT exposed abalone. Furthermore, mRNA expression of Hdh-TEKT4 was significantly higher in sperm with higher motility than in sperm with lower motility during peak breeding season, induced spawning activity stages, and after cryopreservation in different cryoprotectants. Taken together, these results indicate that the expression of Hdh-TEKT4 in Pacific abalone sperm might have a positive correlation with sperm motility.

Augmentation of progestin signaling rescues testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling

Disruption of androgen signaling is known to cause testicular malformation and defective spermatogenesis in zebrafish. However, knockout of cyp17a1, a key enzyme responsible for the androgen synthesis, in ar-/- male zebrafish paradoxically causes testicular hypertrophy and enhanced spermatogenesis. Because Cyp17a1 plays key roles in hydroxylation of pregnenolone and progesterone (P4), and converts 17α-hydroxypregnenolone to dehydroepiandrosterone and 17α-hydroxyprogesterone to androstenedione, we hypothesize that the unexpected phenotype in cyp17a1-/-;androgen receptor (ar)-/- zebrafish may be mediated through an augmentation of progestin/nuclear progestin receptor (nPgr) signaling. In support of this hypothesis, we show that knockout of cyp17a1 leads to accumulation of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and P4. Further, administration of progestin, a synthetic DHP mimetic, is sufficient to rescue testicular development and spermatogenesis in ar-/- zebrafish, whereas knockout of npgr abolishes the rescue effect of cyp17a1-/- in the cyp17a1-/-;ar-/- double mutant. Analyses of the transcriptomes among the mutants with defective testicular organization and spermatogenesis (ar-/-, ar-/-;npgr-/- and cyp17a-/-;ar-/-;npgr-/-), those with normal phenotype (control and cyp17a1-/-), and rescued phenotype (cyp17a1-/-;ar-/-) reveal a common link between a downregulated expression of insl3 and its related downstream genes in cyp17a-/-;ar-/-;npgr-/- zebrafish. Taken together, our data suggest that genetic or pharmacological augmentation of the progestin/nPgr pathway is sufficient to restore testis organization and spermatogenesis in zebrafish with the depletion of androgen signaling.

Differential gene expression pattern and plasma sex steroids during testicular development in Genyatremus luteus (Perciforme: Haemulidae) (Bloch, 1790)

Abstract The aim of the current study is to evaluate gene expression patterns of LH (lhr) and estrogen (er) receptors and plasma steroid levels during testicular development in Genyatremus luteus. Males were histologically classified as immature (n=7), maturing (n=7) and mature (n=7), based on the cellular structure of their testes. Plasma 11-KT concentration recorded peak at the final maturation stage. The highest plasma 17α-OHP concentrations were observed at the immature stage; they decreased at the maturation and mature stages. On the other hand, 17β-estradiol (E2) recorded higher concentrations at the maturation stage. Er expression has significantly increased along the maturational development of animals’ testes. The mRNA observed for the LH receptor has decreased from immature to maturing stage; it presented expression peak at the mature stage. There was high association between receptor gene expression and plasma steroid levels, mainly E2. The current study was the first to feature different reproductive maturation stages in male G. luteus specimens, based on cellular, endocrine and molecular aspects. In addition, it has shown that the gene expression profile for er and lhr receptors, as well as plasma 11-KT and E2 concentrations, are directly linked to testicular maturation, although they are not necessarily associated with the gonadosomatic index.

Induction of Spermiation in Sterlet Acipenser ruthenus by PLGA Microparticle Delivery with Sustained Alarelin Release

Simple Summary

Cultured sterlet Acipenser ruthenus males do not usually undergo spontaneous spermiation, and if any sperm is obtained without hormone treatment, it is generally of diminished quality. We compared efficacy of stimulation of spermiation with carp pituitary extract to that of 35 µg kg⁻¹ or 200 µg kg⁻¹ body weight gonadotropin-releasing hormone analogue in a sustained release system. Hormone treatments caused a significant increase in testosterone and 11-ketotestosterone, as well as induced spermiation. The delivery system based on poly (lactic-co-glycolic acid) microparticles with slow release of Alarelin at 35 µg kg⁻¹ BW effectively induced spermiation, and was associated with extended sperm collection compared to carp pituitary treatment. The sustained delivery system offers an excellent option for spermiation induction in cultured sterlet, and possibly other sturgeon.

Abstract

Carp pituitary treatment versus poly (lactiac-co-glycolic acid) microparticles with slow release of Alarelin at 35 µg kg⁻¹ or 200 µg kg⁻¹ body weight to induce spermiation was compared in sterlet Acipenser ruthenus. All hormone treatments initially increased testosterone and 11-ketotestosterone, with a subsequent decline in testosterone but consistent high levels of 11-ketotestosterone at 48 and 72 h post-treatment. Spermiation did not differ between hormone-treated groups, and was not detected in controls receiving saline solution. Administration of the carp pituitary led to maximum sperm production 24 h post-treatment, followed by a decrease at 48 h post-treatment, with no sperm obtained at 72 h. The effect of Alarelin at 35 µg kg⁻¹ bw and carp pituitary did not differ at 24 and 48 h post-treatment, whereas 200 µg kg⁻¹ bw Alarelin was associated with significantly lower spermatozoon concentration 24 h post-treatment compared to carp pituitary, with no difference in milt volume. Higher relative sperm production was observed 48 h after injection of Alarelin at 200 µg kg⁻¹ bw compared to carp pituitary. Spermatozoon motility was significantly higher in fish receiving Alarelin at 35 µg kg⁻¹ bw than 200 µg kg⁻¹ bw. The treatment with optimal effect on inducing spermiation was poly (lactic-co-glycolic acid) microparticles with slow release of Alarelin at 35 µg kg⁻¹ bw.

Improved conditions of a whole testis organ culture system in terms of spermatogonial proliferation levels in marine medaka (Oryzias dancena)

In vitro spermatogenesis can be performed for marine medaka (Oryzias dancena) via whole testis organ cultures, but spermatogenesis could only be maintained during the early phase of culturing, suggesting that the culture conditions can be further optimized. To improve the culture conditions, we examined the effects of culture temperature, basal media, and medium supplements on spermatogonial proliferation levels during whole testis organ culturing by BrdU incorporation assays. Our results show that a 30°C culture temperature negatively affected spermatogonial proliferation compared to 26°C and 28°C and that the use of Dulbecco's Modified Eagle Medium and Minimum Essential Medium α (α-MEM) was more effective for spermatogonial proliferation than the use of Leibovitz's L-15 Medium (L15). When fetal bovine serum (FBS) was replaced with KnockOut Serum Replacement (KSR), a significantly positive effect was observed for the maintenance of spermatogonial proliferation. However, supplementation of the medium with 17α, 20β-dihydroxy-4-pregnen-3-one did not show any significant effect. Gene expression analyses of four genes, including Nanos2, SCP3, AMH, and StAR, indicated that the optimized culture conditions consisting of α-MEM and KSR had the most positive influence on the maintenance of spermatogonial proliferation levels in whole testis organ cultures compared to the original culture conditions consisting of L15 and FBS by maintaining the function of Sertoli and Leydig cells. The results from this study will provide useful information for the study of in vitro spermatogenesis in fish.

A Review on Environmental Contaminants-Related Fertility Threat in Male Fishes: Effects and Possible Mechanisms of Action Learned from Wildlife and Laboratory Studies

Increasing global rates of diminished fertility in males has been suggested to be associated with exposure to environmental contaminants (ECs). The aquatic environments are the final repository of ECs. As the reproductive system is conserved in vertebrates, studies on the effects of ECs on fertility endpoints in fishes provide us with valuable information to establish biomarkers in risk assessment of ECs, and to understand the ECs-related fertility threat. The aim of the present review was to evaluate associations between ECs and fertility determinants to better understand ECs-related male fertility threat in male fishes. Wildlife studies show that the reproductive system has been affected in fishes sampled from the polluted aquatic environment. The laboratory studies show the potency of ECs including natural and synthetic hormones, alkylphenols, bisphenols, plasticizers, pesticides, pharmaceutical, alkylating, and organotin agents to affect fertility determinants, resulting in diminished fertility at environmentally relevant concentrations. Both wildlife and laboratory studies reveal that ECs adverse effects on male fertility are associated with a decrease in sperm production, damage to sperm morphology, alternations in sperm genome, and decrease in sperm motility kinetics. The efficiency of ECs to affect sperm quality and male fertility highly depends on the concentration of the contaminants and the duration of exposure. Our review highlights that the number of contaminants examined over fertility tests are much lower than the number of contaminants detected in our environment. The ECs effects on fertility are largely unknown when fishes are exposed to the contaminants at early developmental stages. The review suggests the urgent need to examine ECs effects on male fertility when a fish is exposed at different developmental stages in a single or combination protocol. The ECs effects on the sperm genome are largely unknown to understand ECs-related inheritance of reproductive disorders transmitted to the progeny. To elucidate modes of action of ECs on sperm motility, it is needed to study functional morphology of the motility apparatus and to investigate ECs-disrupted motility signaling.

Correlations between environmental salinity levels, blood biochemistry parameters, and steroid hormones in wild juvenile American alligators (Alligator mississippiensis)

American alligators (Alligator mississippiensis) inhabit freshwater wetlands that are vulnerable to salinization caused by anthropogenic alterations to freshwater flow, in addition to storm surges, sea level rise, and droughts. Salinization of coastal freshwater habitats is a growing concern in a changing climate due to increased frequency and intensity of storm surges and drought conditions. This study opportunistically sampled juvenile male and female wild alligators in various salinities each month excluding November, December, and January for one year at Rockefeller Wildlife Refuge in coastal Louisiana. Blood plasma biochemistry parameters including electrolyte levels were subsequently measured. In addition, levels of various renin-angiotensin-aldosterone system hormones, glucocorticoids, androgens, estrogens, and progestogens were analyzed using liquid chromatography and tandem mass spectrometry. Only males were sampled in hyperosmotic environments (> 10‰) during dry conditions in late summer 2018. In juvenile males, plasma Na⁺, Cl^-, and the progestogen 17α,20β-dihydroxypregnenone were significantly and positively correlated with environmental salinity. However, variation in glucocorticoids, androgens, and estrogens were not associated with hypersaline water while sex steroids showed significant seasonal variation. This study demonstrated significant correlation of environmental salinity with electrolyte levels and a sex steroid in wild juvenile alligators, and to our knowledge represents the first measurement of 17α,20β-dihydroxypregnenone in alligators.

The effects of norethindrone on the ontogeny of gene expression along the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-gonadal axes in zebrafish (Danio rerio)

Little is known about the molecular effects of progestins on the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes in fish prior to sexual differentiation. In this study, the effects of norethindrone (NET) on the ontogeny of HPG- and HPA-related genes in zebrafish embryo/early larvae prior to sexual differentiation were evaluated. Embryo/larvae were exposed to different concentrations (5, 50, 500 ng/L) of NET for 6 days. The levels of the transcripts of the genes closely related to the HPG and HPA axes were determined daily during 3 stages (embryo, embryo/larvae transition, and early larvae). The results showed that most genes were up-regulated and the ontogeny of genes in the HPA axis was earlier than that of HPG axis, especially for the upstream genes of both the HPG (gnrh2, gnrh3, fshb, lhb) and the HPA (crh, pomc, star) axes. In contrast, the transcriptional expressions of genes of the cortisol/stress pathway (cyp11b, mr) were inhibited and those of the progesterone pathway were not affected. More importantly, NET exposure induced the expressions of the genes (esr1, vtg1, hsd17b3, hsd11b2, ar) that are closely related to the steroid hormone pathways in the embryos/larvae stages, implying a precocious effects of NET in zebrafish. This study demonstrates that NET alters the expression of HPA- and HPG-axes related genes in zebrafish at early stages, pointing to the need for the same type of analysis during the zebrafish gonadal differentiation window.

Regulation of endocrine systems by the microbiome: Perspectives from comparative animal models

The microbiome regulates endocrine systems and influences many aspects of hormone signaling. Using examples from different animal taxa, we highlight the state of the science in microbiome research as it relates to endocrinology and endocrine disruption research. Using a comparative approach discussing fish, birds, and mammals, we demonstrate the bidirectional interaction between microbiota and hormone systems, presenting concepts that include (1) gastrointestinal microbiome regulation of the neuroendocrine feeding axis; (2) stress hormones and microbial communities; (3) the role of site-specific microbiota in animal reproduction; (4) microbiome effects on the neuroendocrine systems and behavior; and (5) novel mechanisms of endocrine disruption through the microbiome. This mini-review demonstrates that hormones can directly affect the richness and diversity of microbiota and conversely, microbiota can influence hormone production and mediate their functions in animals. In addition, microbiota can influence the action of a diverse range of neurotransmitters and neuropeptides in the central nervous system, which can lead to behavioral disruptions. As many animals have species-specific reproductive behaviors, it is important to understand how shifts in the microbiota relate to these complex interactions between sexes. This is especially important for captive animals on specialized diets, and there are significant implications for microbiome research in conservation and reproductive biology. For example, microbial metabolites may modify motility of gametes or modulate hormone-receptor interactions in reproductive tissues. Thus, efforts to incorporate metabolomics into the science of microbiome-endocrine relationships, both those produced by the host and those generated from microbial metabolism, are increasingly needed. These concepts have fostered an exciting emerging era in comparative endocrinology.

Steroidogenesis and its regulation in teleost-a review

Steroid hormones modulate several important biological processes like metabolism, stress response, and reproduction. Steroidogenesis drives reproductive function wherein development and differentiation of undifferentiated gonads into testis or ovary, and their growth and maturation, are regulated. Steroidogenesis occurs in gonadal and non-gonadal tissues like head kidney, liver, intestine, and adipose tissue in teleosts. This process is regulated differently through multi-level modulation of promoter motif transcription factor regulation of steroidogenic enzyme genes to ultimately control enzyme activity and turnover. In view of this, understanding teleostean steroidogenesis provides major inputs for technological innovation of pisciculture. Unlike higher vertebrates, steroidal intermediates and shift in steroidogenesis is critical for gamete maturation in teleosts, more essentially oogenesis. Considering these characteristics, this review highlights the promoter regulation of steroidogenic enzyme genes by several transcription factors that are involved in teleostean steroidogenesis. It also addresses different methodologies involved in promoter regulation studies together with glucocorticoids and androgen relationship with reference to teleosts.

11-Oxygenated androgens in health and disease

The adrenal gland is a source of sex steroid precursors, and its activity is particularly relevant during fetal development and adrenarche. Following puberty, the synthesis of androgens by the adrenal gland has been considered of little physiologic importance. Dehydroepiandrosterone (DHEA) and its sulfate, DHEAS, are the major adrenal androgen precursors, but they are biologically inactive. The second most abundant unconjugated androgen produced by the human adrenals is 11β-hydroxyandrostenedione (11OHA4). 11-Ketotestosterone, a downstream metabolite of 11OHA4 (which is mostly produced in peripheral tissues), and its 5α-reduced product, 11-ketodihydrotestosterone, are bioactive androgens, with potencies equivalent to those of testosterone and dihydrotestosterone. These adrenal-derived androgens all share an oxygen atom on carbon 11, so we have collectively termed them 11-oxyandrogens. Over the past decade, these androgens have emerged as major components of several disorders of androgen excess, such as congenital adrenal hyperplasia, premature adrenarche and polycystic ovary syndrome, as well as in androgen-dependent tumours, such as castration-resistant prostate cancer. Moreover, in contrast to the more extensively studied, traditional androgens, circulating concentrations of 11-oxyandrogens do not demonstrate an age-dependent decline. This Review focuses on the rapidly expanding knowledge regarding the implications of 11-oxyandrogens in human physiology and disease.

New insights into the role of mTORC1 in male fertility in zebrafish

Mechanistic target of rapamycin complex 1 (mTORC1) plays crucial roles in male fertility. In mammals, deregulation of mTORC1 led to disordered spermatogonia proliferation and spermatogenesis, which eventually caused infertility in males. However, its roles in male fertility of non-mammalian species remain unclarified. In the present study, it was found that treatment of rapamycin, an mTORC1 inhibitor, resulted in infertility with decreased milt production and sperm motility in zebrafish. However, it is surprising to find that spermatogenesis was normal in these fish. All types of germ cells were found and the proliferation of spermatogonia and spermatocyte were normal. These results suggested that maturation of sperm may be impaired in males treated with rapamycin. Increased apoptosis was found surrounding the lumen containing spermatozoa, implicating a loss of Sertoli cells in testes treated with rapamycin. Moreover, LH/hCG mediated up-regulation of steroidogenic genes was abolished. The expression of npr and ar induced by LH/hCG was also blocked, which further suppressed the signaling of progestin and androgen. Collectively, mTORC1 maintains male fertility via different mechanisms in fish and mammals. mTORC1 is dispensable for spermatogenesis in zebrafish, but possibly supports the maintenance of Sertoli cells and mediates the signaling of hormones, which are crucial for sperm maturation.

Induction of sperm hypermotility through membrane progestin receptor alpha (mPRα): A teleost model of rapid, multifaceted, nongenomic progestin signaling

Rapid progestin effects on sperm physiology have been described in a variety of vertebrate species. Here, we briefly review the signaling pathways mediating rapid progestin induction of sperm hypermotility and increased fertility in two teleost species, Atlantic croaker and southern flounder. Acute in vitro treatment of teleost sperm with the progestin hormone, 20β-S, causes activation of progestin membrane receptor alpha (mPRα, or Paqr7) coupled to a stimulatory olfactory G protein (G_olf), resulting in increased cAMP and calcium concentrations and hypermotility upon activation in a hyperosmotic medium. Pharmacological tools were used to investigate the involvement of mPRα and several intracellular signaling pathways in the hypermotility response. Evidence was obtained using the specific mPRα agonist, Org OD 02-0, that this progestin action is mediated through mPRα and not through the nuclear PR. The results indicate that progestins induce hypermotility through activation of a membrane adenylyl cyclase (Acy)/cAMP pathway, an epidermal growth factor receptor (Egfr)/Mapkinase pathway, and a Pi3kinase/Akt/phosphodiesterase (Pde) pathway which result in increased sperm calcium concentrations within 10 s. The finding that inhibition of any one of these pathways is sufficient to prevent hypermotility along with the calcium increase suggests that activation of all of them and the associated calcium increase are required for the progestin hypermotility response. On the basis of these findings a model of progestin induction of sperm hypermotility in teleosts is proposed. As teleosts lack CatSper, the model described here is a non-CatSper mediated one and may therefore be applicable to a wide variety of nonmammalian vertebrates.

Sperm motility in fishes: (III) diversity of regulatory signals from membrane to the axoneme

Fish spermatozoa acquire potential for motility in the sperm duct where they are immotile. Osmolality of the seminal plasma is a key factor to maintain spermatozoa in the quiescent state in either freshwater or marine fishes. However, potassium (K⁺) ions prevent spermatozoa motility in salmonid and sturgeon fishes, while CO₂ inhibits spermatozoa motility in flatfishes. Once, spermatozoa are released at spawning, their motility is initiated in hypo-osmotic and hyper-osmotic environments in freshwater and marine fishes, respectively. Some substances produced by the testes (a progestin), or released from oocytes (peptides) induce spermatozoa hypermotility in some marine fishes including the Atlantic croaker and Pacific herrings, respectively. Duration of spermatozoa motility is short, lasting for a few seconds to few minutes in most fishes due to rapid depletion of energy required for the beating of the motility apparatus called axoneme. In the osmotic-activated spermatozoa, K⁺ and water effluxes occur in freshwater and marine fishes, respectively, which trigger spermatozoa motility signaling. In general, initiation of axonemal beating is associated with an increase in intracellular calcium (Ca²⁺) ions in spermatozoa of both freshwater and marine fishes and a post- or pre-increase in intracellular pH, while cyclic adenosine monophosphate (cAMP) remains unchanged. However, axonemal beating is cAMP-dependent in demembranated spermatozoa of salmonid and sturgeon fishes. Calcium from extracellular environment or intracellular stores supply required Ca²⁺ concentration for axonemal beating. Several axonemal proteins have been so far identified in fishes that are activated by Ca²⁺ and cAMP, directly or mediated by protein kinase C and protein kinase A, respectively. The present study reviews differences and similarities in complex regulatory signals controlling spermatozoa motility initiation in fishes, and notes physiological mechanisms that await elucidation.

Nuclear progestin receptor (Pgr) knockouts resulted in subfertility in male tilapia (Oreochromis niloticus)

It was documented that 17α, 20β-dihydroxy-4-pregnen-3-one (DHP), a fish specific progestin, might play critical roles in spermatogenesis, sperm maturation and spermiation partially through activating nuclear receptor (Pgr). However, no direct evidence is available to demonstrate the functions of DHP in fish spermatogenesis. To further elucidate the roles of DHP in teleosts, we generated a pgr homozygous mutant line in XY Nile tilapia (Oreochromis niloticus). Pgr gene mutation resulted in the development of a smaller, thinner testis and a lower GSI compared with normal testis. Pgr gene knockout led to irregular arrangement of spermatogenic cysts, decline of sperm count and sperm motility. Significant decrease of spermatocytes and spermatozoa was observed, which was further proved by the PCNA and Ph3 staining. Real-time PCR analysis demonstrated that mutation of pgr gene resulted in a significant up-regulation of steroidogenesis-related genes of cyp17a, cyp11b2, StAR, scc, 20β-HSD, and sf1, and down-regulation of fshb, fshr, oct4, sycp3, cdk1, prm, cyclinB1, cyclinB2 and cdc25 genes. Furthermore, both Immunohistochemistry and Western blotting experiments revealed a remarkable increase of Cyp17a1, Cyp17a2 and Cyp11b2 expressions in the pgr^-/- testis. EIA measurement showed that an evident increase of 11-KT level was found in the pgr^-/- XY fish. There was a significant increase in the mortality of offspring when crossing pgr^-/- XY fish with wild type XX fish. Increased TUNEL staining and enhanced apoptosis maker gene (bax) expressions were also observed. Taken together, our data suggested that DHP-activated physiology via pgr is crucial for the fertility in the XY tilapia.

Effect of hCG and Ovaprim™ on reproductive characteristics of male Levantine scraper, Capoeta damascina (Valenciennes, 1842)

Species richness and abundance within the genus Capoeta has been depleted. As such, there is great need for developing assisted reproductive technologies for controlling reproduction in captivity. Here, we conducted in vivo studies with single administrations of human chorionic gonadotropin (hCG) and Ovaprim™ [(D-Arg⁶, Pro⁹NEt)-sGnRH + domperidone] in wild-caught Levantine scraper, Capoeta damascina and then evaluated milt characteristics, fertilization success, serum sex steroids, and spermatogenesis via histological testicular development. Spermiation responses were significantly stronger for Ovaprim injected fish than those injected with hCG or saline. hCG had a negative effect on milt quality by reducing the percentage of motile sperm and fertilization success at 12-48 h post injection (hpi), which was not observed after treatment with Ovaprim or the saline injection. Hormonal therapy resulted in higher sperm densities and spermatocrit, although sperm longevity was not impacted. Sex steroids were not impacted by hCG or saline injection, but Ovaprim effectively induced androgen and progestin release, as evident by higher serum levels of testosterone, and 17α,20β-dihydroxy-4-pregnen-3-one. Consequently, their levels peaked at 12 hpi, which coincided with maximal milt production. Histological analysis of the testes and quantification of germ cell types revealed that Ovaprim significantly stimulated spermiogenesis, as a higher number of accumulated spermatozoa were observed at 12 h and 24 hpi. Testes from saline and hCG-injected fish remained unchanged through the experiment, and contained all stages of germ cells, predominantly spermatocytes with few spermatozoa. In conclusion, Ovaprim treatment successfully induced steroidogenesis and maturation of spermatogenic germ cells, leading to spermiation and milt production without having any negative impacts on sperm quality and fertility in wild-caught C. damascina.

Effects of Sex Steroids on Fish Leukocytes

In vertebrates, in addition to their classically reproductive functions, steroids regulate the immune system. This action is possible mainly due to the presence of steroid receptors in the different immune cell types. Much evidence suggests that the immune system of fish is vulnerable to xenosteroids, which are ubiquitous in the aquatic environment. In vivo and in vitro assays have amply demonstrated that oestrogens interfere with both the innate and the adaptive immune system of fish by regulating the main leukocyte activities and transcriptional genes. They activate nuclear oestrogen receptors and/or G-protein coupled oestrogen receptor. Less understood is the role of androgens in the immune system, mainly due to the complexity of the transcriptional regulation of androgen receptors in fish. The aim of this manuscript is to review our present knowledge concerning the effect of sex steroid hormones and the presence of their receptors on fish leukocytes, taking into consideration that the studies performed vary as regard the fish species, doses, exposure protocols and hormones used. Moreover, we also include evidence of the probable role of progestins in the regulation of the immune system of fish.

The Rise, Fall, and Resurrection of 11-Oxygenated Androgens in Human Physiology and Disease

The 11-oxyandrogens, particularly 11-ketotestosterone, have been recognized as a biologically important gonadal androgen in teleost (bony) fishes for decades, and their presence in human beings has been known but poorly understood. Today, we recognize that 11-oxyandrogens derive from the human adrenal glands and are major bioactive androgens, particularly in women and children. This article will review their biosynthesis and metabolism, abundance in normal and pathologic states, and potential as biomarkers of adrenal developmental changes and disease. Specifically, 11-oxyandrogens are the dominant active androgens in many patients with 21-hydroxylase deficiency.

Androgen responses to reproductive competition of males pursuing either fixed or plastic alternative reproductive tactics

Alternative reproductive tactics (ARTs), which can be plastic or fixed for life, may be characterized by distinct hormonal profiles. The relative plasticity hypothesis predicts flexible androgen regulation for adult males pursuing plastic tactics, but a less flexible regulation for males using a fixed tactic throughout life. Furthermore, androgen profiles may respond to changes in the social environment, as predicted by the social reciprocity models of hormone/behaviour interactions. The cichlid fish Lamprologus callipterus provides a rare opportunity to study the roles of androgens for male ARTs within a single species, because fixed and plastic ARTs coexist. We experimentally exposed males to competitors pursuing either the same or different tactics to test predictions of the relative plasticity and the social reciprocity models. Androgen profiles of different male types partly comply with predictions derived from the relative plasticity hypothesis: males of the plastic bourgeois/sneaker male trajectory showed different 11-ketotestosterone (11-KT) levels when pursuing either bourgeois or parasitic sneaker male behaviours. Surprisingly, males pursuing the fixed dwarf male tactic showed the highest free and conjugated 11-KT and testosterone (T) levels. Our experimental social challenges significantly affected the free 11-KT levels of bourgeois males, but the androgen responses did not differ between challenges involving different types of competitors. Furthermore, the free T-responses of the bourgeois males correlated with their aggressive behaviour exhibited against competitors. Our results provide new insights into the endocrine responsiveness of fixed and plastic ARTs, confirming and refuting some predictions of both the relative plasticity and the social reciprocity models.

Progestin increases the expression of gonadotropins in pituitaries of male zebrafish

Our previous study showed that the in vivo positive effects of 17α,20β-dihydroxy-4-pregnen-3-one (DHP), the major progestin in zebrafish, on early spermatogenesis was much stronger than the ex vivo ones, which may suggest an effect of DHP on the expression of gonadotropins. In our present study, we first observed that fshb and lhb mRNA levels in the pituitary of male adult zebrafish were greatly inhibited by 3 weeks exposure to 10nM estradiol (E2). However, an additional 24h 100nM DHP exposure not only reversed the E2-induced inhibition, but also significantly increased the expression of fshb and lhb mRNA. These stimulatory effects were also observed in male adult fish without E2 pretreatment, and a time course experiment showed that it took 24h for fshb and 12h for lhb to respond significantly. Because these stimulatory activities were partially antagonized by a nuclear progesterone receptor (Pgr) antagonist mifepristone, we generated a Pgr-knockout (pgr(-/-)) model using the TALEN technique. With and without DHP in vivo treatment, fshb and lhb mRNA levels of pgr(-/-) were significantly lower than those of pgr(+/+) Furthermore, ex vivo treatment of pituitary fragments of pgr(-/-) with DHP stimulated lhb, but not fshb mRNA expression. Results from double-colored fluorescent in situ hybridization showed that pgr mRNA was expressed only in fshb-expressing cells. Taken together, our results indicated that DHP participated in the regulation of neuroendocrine control of reproduction in male zebrafish, and exerted a Pgr-mediated direct stimulatory effect on fshb mRNA at pituitary level.

17,20β-P and cortisol are the main in vitro metabolites of 17-hydroxy-progesterone produced by spermiating testes of Micropogonias furnieri (Desmarest, 1823) (Perciformes: Sciaenidae)

The aim was to investigate the major C21 steroids produced by spermiating white croaker Micropogonias furnieri (Sciaenidae) in order to establish the potential mediator of gamete maturation in males of this species. The testes steroid production at the spawning season was identified incubating the 3H-17-hydroxy-4-pregnene-3,20-dione precursor through thin layer chromatography, high pressure liquid chromatography, enzymatic oxydation, acetylation and immunochemistry analyses. 17,20β-Dihydroxy-4-pregnen-3-one (17,20β-P) and 11β,17,21-Trihydroxy-4-pregnene-3,20-dione (cortisol) were the main metabolites produced. Contrary to what we expected, 17,20β,21-Trihydroxy-4-pregnen-3-one was not detected. Circulating levels of 17,20β-P were undetectable in immature testes and in those at the first spermatogenesis stages, while a clear increase was observed during the whole spermatogenesis and spermiation phases (from undetectable to 1047 pg mL-1). In vitro studies together with plasma detection suggest that 17,20β-P is a good steroid candidate involved in M. furnieri testes maturation. The role of cortisol during late phases of testes development needs further studies.

Spermatogenesis and related plasma androgen and progestin level in wild male golden mahseer, Tor putitora (Hamilton, 1822), during the spawning season

Testicular development and plasma levels of sex steroid [11-ketotestosterone (11-KT), testosterone (T) and 17,20β-dihydoxy-4-pregnen-3-one (17,20β-P)] were studied for the first time in wild golden mahseer, Tor putitora. Testicular development was investigated by macroscopic observation and histology of the gonads, whereas steroids were measured by enzyme-linked immunosorbent assay. Based on macroscopic observation and germ cell types present in gonad histology, the testes of T. putitora were divided into five developmental stages: immature [stage I; spermatogonia (SPG)], early spermatogenesis [stage II; SPG and spermatocytes (SPC)], late spermatogenesis [stage III; SPG, SPC, spermatids (SPD) and spermatozoa (SPZ)], spermiation (stage IV; SPZ) and post-spawning (stage V; SPG, SPD and SPZ). During the stage I of the testes, the lowest levels of plasma sex steroid and gonadosomatic index (I G) were recorded. The highest plasma level of T was 0.89 ± 0.09 ng/mL and 11-KT was 4.23 ± 0.54 ng/mL, which was during the stage III and IV, respectively. The peak in 11-KT was coincident with the peak in I G (1.65 ± 0.12 %). The lowest T and 11-KT levels were 0.25 ± 0.02 ng/mL and 0.47 ± 0.09 ng/mL, respectively, which was at stage I. Plasma levels of 17,20β-P increased significantly at stage III (1.04 ± 0.06 ng/mL) and stage IV testes (1.28 ± 0.03 ng/mL) and then declined in post-spawned fish. This indicates that 17,20β-P could also be a possible maturation-inducing steroid in this fish. The condition factor (K) significantly decreased during the testicular development and was lowest at spermiation stage (0.53 ± 0.02 %). The proportion of running male peaked concomitantly with the appearance of stage IV testes. Presence of germ cells of different developmental stages indicates that T. putitora male is a multiple spawner, and the information generated here is important for developing a captive breeding, culture and conservation programs for this endangered coldwater Himalayan fish species.

Effect of the probiotic Lactobacillus rhamnosus on the expression of genes involved in European eel spermatogenesis

Positive effects of probiotics on fish reproduction have been reported in several species. In the present study, 40 male European eels were weekly treated with recombinant hCG for 9 weeks and with three different concentrations (10(3), 10(5), and 10(6) CFU/mL) of probiotic Lactobacillus rhamnosus IMC 501 (Sinbyotec, Italy). The probiotics were daily added to the water from the sixth week of the hCG treatment. Males from the treated and control groups were sacrificed after 1, 2, and 3 weeks of probiotic treatment (seventh-ninth weeks of hCG treatment); at this point, sperm and testis samples were also collected. Sperm volume was estimated, and motility was analyzed by computer-assisted sperm analysis software. Alternations in transcription of specific genes involved in reproductive process such as activin, androgen receptors α and β (arα and arβ), progesterone receptor 1 (pr1), bone morphogenetic protein 15 (bmp15), and FSH receptor (fshr) were analyzed in the testis. After 2 weeks of probiotic treatment, sperm production and sperm motility parameters (percentage of motile cells and percentage of straight-swimming spermatozoa) were increased in the European eel treated with 10(5) CFU/mL compared to controls or to the other probiotic doses. These changes were associated with increases in messenger RNA expression of activin, arα, arβ, pr1, and fshr. Conversely, after 3 weeks, activin and pr1 expression decreased. No significant changes were observed on bmp15 expression throughout the duration of the treatment with 10(5) CFU/mL dose. The lowest and highest probiotic dose (10(3) and 10(6) CFU/mL, respectively) inhibited the transcription of all genes along all the experiment, except for arα and arβ after 1 week of probiotic treatment when compared to controls. The changes observed by transcriptomic analysis and the sperm parameters suggest that a treatment with L rhamnosus at 10(5) CFU/mL for 2 weeks could improve spermatogenesis process in Anguilla anguilla.

Di-(2-ethylhexyl)-phthalate disrupts pituitary and testicular hormonal functions to reduce sperm quality in mature goldfish

Di-(2-ethylhexyl) phthalate (DEHP) interferes with male reproductive endocrine system in mammals, however its effects on fish reproduction are largely unknown. We evaluated sperm quality and investigated reproductive endocrine system in mature goldfish (Carassius auratus) exposed to nominal 1, 10, and 100μg/L DEHP. To examine DEHP estrogenic activity, one group of goldfish was exposed to 17β-estradiol (5μg/L E2) for comparison. Following 30d of exposure, sperm production was decreased and suppressed in DEHP and E2 treated goldfish, respectively. Sperm motility and velocity were decreased in goldfish exposed to 100 and 10μg/L DEHP at 15s post-sperm activation, respectively. Compared to control, 11-ketotestosterone (11-KT) levels were decreased at 10 and 1μg/L DEHP at day 15 and 30, respectively. In E2 treated goldfish, 11-KT levels were decreased compared to control during the period of exposure. E2 levels were increased in goldfish exposed to E2, but remained unchanged in DEHP treated goldfish during the period of exposure. StAR mRNA levels encoding regulator of cholesterol transfer to steroidogenesis were decreased in DEHP and E2 treated goldfish following 15 and 30d of exposure, respectively. Luteinizing hormone (LH) levels were decreased in DEHP and E2 treated goldfish following 15 and 30d of exposure, respectively. In DEHP treated goldfish, gnrh3, kiss1 and its receptor (gpr54) mRNA levels did not change during the experimental period. In E2 treated goldfish, gnrh3 mRNA levels were decreased at day 7, but kiss1 and gpr54 mRNA levels were increased at day 30 of exposure. The mRNA levels of genes encoding testicular LH and androgen receptors remained unchanged in DEHP and E2 treated goldfish. In contrast to E2 treated goldfish, vitellogenin production was not induced in DEHP treated goldfish and mRNA levels of genes with products mediating estrogenic effects remained unchanged or decreased. In conclusion, DEHP interferes with testis and pituitary hormonal functions to reduce sperm quality in goldfish and does not exhibit estrogenic activity.

Blocking of progestin action disrupts spermatogenesis in Nile tilapia (Oreochromis niloticus)

In vitro studies have indicated that the maturation-inducing hormone 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-DP, DHP), probably through nuclear progestin receptor (Pgr), might be involved in the proliferation of spermatogonial cells and the initiation of meiosis in several fish species. However, further in vivo evidence is required to elucidate the role of DHP in spermatogenesis during sexual differentiation in teleosts. In this study, we cloned pgr and analyzed its expression in Nile tilapia (Oreochromis niloticus) and treated XY fish with RU486 (a synthetic Pgr antagonist) from 5 days after hatching (dah) to determine the role of DHP in spermatogenesis. Sequence and phylogenetic analyses revealed that the Pgr identified in tilapia is a genuine Pgr. Pgr was found to be expressed in the Sertoli cells surrounding spermatogonia and spermatids in the testis of tilapia. Real-time PCR analysis revealed that the expression of pgr in the testis was significantly upregulated from 10 dah, further increased at 50 dah, and persisted until adulthood in fish. In the testis of RU486-treated fish, the transcript levels of germ cell markers and a meiotic marker were substantially reduced. However, the expression of markers in Sertoli cells remained unchanged. Moreover, the production of 11-ketotestosterone and the expression of genes encoding various steroidogenic enzymes were also not altered. In contrast, the expression of cyp17a2, encoding one of the critical steroidogenic enzymes involved in DHP biosynthesis, declined significantly, possibly indicating the inhibition of DHP production by RU486. RU486 treatment given for 2 months did not affect spermatogenesis; however, treatment given for more than 3 months resulted in a decrease in spermatogonial cell numbers and depletion of later-phase spermatogenic cells. Simultaneous excessive DHP supplementation restored spermatogenesis in RU486-treated XY fish. Taken together, our data further indicated that DHP, possibly through Pgr, might be essential for spermatogonial cell proliferation and spermatogenesis in fish.

Membrane progestin receptor alpha mediates progestin-induced sperm hypermotility and increased fertilization success in southern flounder (Paralichthys lethostigma)

Progestin hormones stimulate sperm motility in teleosts but their mechanisms of action remain unclear. Preliminary results suggest that progestin upregulation of sperm motility in southern flounder and several other marine species is mediated through a sperm membrane progestin receptor with the characteristics of membrane progestin receptor alpha (mPRα, also known as Paqr7b). The hypothesis that mPRα has an important role in progestin regulation of southern flounder sperm motility and fertility was tested in the present study. The specific mPRα agonist, 10-ethenyl-19-norprogesterone (Org OD 02-0, 100nM), mimicked the stimulatory actions of the endogenous progestin, 17,20β, 21-trihydroxy-4-pregnen-3-one (20β-S, 100nM) on flounder sperm motility. The concentration of the mPRα protein on sperm plasma membranes was positively correlated to sperm motility as well as the responsiveness of sperm to progestin stimulation. Acute in vitro progestin treatment of sperm with high mPRα protein levels increased both sperm motility and fertilization success in strip spawning experiments. However, in vitro progestin treatments were ineffective on sperm with low receptor abundance. A single injection of the superactive gonadotropin-releasing hormone analog (LHRHa, 100μg/kg) increased sperm motility and fertilization success in strip spawning experiments 72h post-injection which was accompanied by an increase in mPRα protein concentrations on sperm plasma membranes. These results provide clear evidence that southern flounder sperm hypermotility is mediated through mPRα. Stimulatory G proteins, but not inhibitory G proteins, were identified in flounder sperm plasma membrane fractions. The finding that treatment of flounder sperm plasma membrane fractions with either 20β-S or Org OD 02-0 increases cAMP levels suggests progestins stimulate flounder sperm motility by activating an mPRα/stimulatory G protein/membrane adenylyl cyclase pathway. A similar mechanism has been identified in Atlantic croaker, suggesting that the signaling pathway mediated by mPRα in sperm is highly conserved in advanced teleosts. Collectively, our results indicate that progestin-stimulation of flounder sperm hypermotility and fertility is dependent on a sufficient concentration of mPRα which can be upregulated by in vivo LHRHa treatments. These findings potentially have practical applications for enhancing the fertility of male flounder broodstock.

Current and future assisted reproductive technologies for fish species

The Food and Agriculture Organization of the United Nations (FAO) estimates that in 2012 aquaculture production of fish will meet or exceed that of the capture fisheries for the first time. Thus, we have just turned the corner from a predominantly hunting gathering approach to meeting our nutritional needs from fish, to a farming approach. In 2012, 327 finfish species and five hybrids were covered by FAO aquaculture statistics, although farming of carps, tilapias, salmonids, and catfishes account for most of food-fish production from aquaculture. Although for most major species at least part of production is based on what might be considered domesticated animals, only limited production in most species is based on farming of improved lines of fish or is fully independent of wild seedstock. Consistent with the infancy of most aquaculture industries, much of the development and implementation of reproductive technologies over the past 100 years has been directed at completion of the life cycle in captivity in order to increase seed production and begin the process of domestication. The selection of species to farm and the emphasis of selective breeding must also take into account other ways to modify performance of an animal. Reproductive technologies have also been developed and implemented to affect many performance traits among fishes. Examples include technologies to control gender, alter time of sexual maturation, and induce sterilization. These technologies help take advantage of sexually dimorphic growth, overcome problems with growth performance and flesh quality associated with sexual maturation, and genetic containment. Reproductive technologies developed to advance aquaculture and how these technologies have been implemented to advance various sectors of the aquaculture industry are discussed. Finally, we will present some thoughts regarding future directions for reproductive technologies and their applications in finfish aquaculture.

Sperm characteristics and androgens in Acipenser ruthenus after induction of spermiation by carp pituitary extract or GnRHa implants

Spermiation and changes in androgen (testosterone, T and 11-ketotestosterone, 11-KT) levels were studied in sterlet (Acipenser ruthenus) treated with GnRH agonist implants (DAla(6)-Pro(9)-LHRHa) at 25 and 75 μg kg(-1) b.w. and compared with those males treated with 4 mg kg(-1) b.w. of carp pituitary extract (CPE) and 3 pellets of Ovopel kg(-1) b.w., which contains DAla(6)-Pro(9)NEt-mGnRH and metoclopramide. Sperm quality (sperm mass, spermatozoa concentration and sperm motility and velocity) was evaluated 24, 48 and 72 h after hormonal treatments. Males did not release sperm in the control group injected with physiological solution, while sperm could not be collected 7 days after treatments in all hormonally treated groups. Spermiation rates were 100 % in the CPE and Ovopel groups and 25-50 % in the GnRHa-treated groups. Sperm production was significantly lower in the GnRHa-treated groups than in the CPE and Ovopel groups and decreased 72 h after hormonal treatment. Sperm motility and velocity were higher in the Ovopel and GnRHa (75 μg) groups compared to the CPE and GnRHa (25 μg) groups and decreased 72 h after hormonal treatment. Androgens were only affected in spermiating males and changed in the Ovopel and GnRHa (75 μg) after hormonal treatment. Significant correlations were observed between sperm production, sperm motility and sperm velocity, but not androgens. The present study suggests involvement of dopamine in sturgeon spawning. Additionally, better sperm quality observed in the Ovopel group and particularly sperm motility in the GnRHa (75 μg) suggests enhancement of sperm quality in sturgeon treated with GnRHa. Therefore, further study is needed to induce fully spermiation using GnRHa implants in combination with a dopamine inhibitor.

Assessment of spermatogenesis and plasma sex steroids in a seasonal breeding teleost: a comparative study in an area of influence of a tributary, downstream from a hydroelectric power dam, Brazil

River damming and building of hydroelectric power plants interrupt the reproductive migration routes and change the major physicochemical parameters of water quality, with drastic consequences for populations of migratory fishes. The goal of this study was to evaluate proliferation and cell death during spermatogenesis and serum profiles of sex steroids in Prochilodus argenteus, from the São Francisco River, downstream from the Três Marias Dam. A total of 257 adult males were caught quarterly during a reproductive cycle in two sites: the first 34 km of the river after the dam (site 1) and the second 34-54 km after the dam (site 2), after the confluence with a tributary, the Abaeté River. Seasonal changes in the testicular activity associated with morphometric analyses of germ cells as well as proliferation and testicular apoptosis support a more active spermatogenesis in fish from site 2, where higher levels of sex steroids and gonadosomatic index (GSI) were also found. In site 1, fish presented low serum levels of testosterone, 17β-estradiol and 17α-hydroxyprogesterone and a low GSI during gonadal maturation. Spermatogonial proliferation (PCNA) and apoptosis (TUNEL) were more elevated in fish from site 1, but spermatocytes were mainly labelled in fish from site 2. Overall, these data demonstrate changes in testicular activity and plasma sex steroids in a neotropical teleost fish living downstream from a hydroelectric dam, supplying new data on fish reproduction in regulated rivers. Moreover, morphometric analyses associated with sex steroids profiles provide reliable tools to assess fish spermatogenesis under environmental stress conditions.

Effect of pH and cation concentrations on spermatozoan motility of sea trout (Salmo trutta m. trutta L.)

Environmental conditions during external fertilization in fish have a significant effect on spermatozoan motility (MOT) and fertilization ability. Even in the same family of fish, spermatozoa might differ in sensitivity to ions present in the external medium. Elucidation of such differences within a species would help to understand spermatozoan biology and to determine external conditions that would optimize spermatozoan MOT and successful fertilization. Objectives of the current study were to determine the effects of pH and of sodium, potassium, and calcium ion concentrations in the activation solution on sea trout spermatozoan MOT. Six parameters characterizing MOT (MOT, curvilinear velocity [VCL], linearity, amplitude of lateral head displacement, beat cross frequency, and duration of MOT) in spermatozoa activated in prepared buffers were traced by computer-assisted sperm analysis. Sea trout spermatozoa were motile over a wide range of pH values, and increasing pH did influence MOT, VCL, linearity, amplitude of lateral head displacement, and MOT duration. The optimum pH for sperm MOT was established at approximately 10. Increasing K(+) ion concentration within the observed range caused a decrease in MOT and VCL. Spermatozoan movement ceased at 8 mM KCl concentrations. In Ca(2+) buffers, sperm were motile within the range of 0 to 70 mM CaCl(2) concentration; although beyond 8 mM concentration, VCL and MOT gradually declined. Spermatozoan aggregation was observed at the highest ion concentrations tested. Increasing CaCl(2) concentration affected MOT pattern from initiation to termination of spermatozoan movement in a similar manner as changes associated with increasing pH. At concentrations of CaCl(2) higher than 0.5 mM and in buffers with pH values 10 to 11, movement of spermatozoa was characterized by high initial linearity followed by its gradual reduction. In contrast to the effects of KCl and CaCl(2), increasing NaCl concentration up to 90 mM Na(+) concentration prolonged the duration of spermatozoan movement and, up to 60 mM Na(+) concentration, slightly increased sperm velocity as well. Above the concentration of 90 mM NaCl, these parameters decreased; and at 240 mM of Na(+), spermatozoa did not activate.

Anti-androgen vinclozolin impairs sperm quality and steroidogenesis in goldfish

In mammals, vinclozolin (VZ) is known as anti-androgen, which causes male infertility via androgen receptor (AR) antagonism. In aquatic animals, the VZ effects on reproductive functions are largely unknown and results are somewhat contradictory. To understand VZ adverse effects on male reproduction, mature goldfish (Carassius auratus) were exposed to three nominal VZ concentrations (100, 400, and 800 μg/L) and alternations in gonadosomatic (GSI) and hepatosomatic indices (HSI), 17β-estradiol (E(2)), 11-ketotestosterone (11-KT) and sperm quality were investigated compared to the solvent control. One group was exposed to E(2) (nominal concentration of 5 μg/L), an estrogenic compound, as a negative control. Following one month exposure, GSI and HSI were unchanged in all VZ treated groups compared to solvent control. Sperm volume, motility and velocity were reduced in fish exposed to 800 μg/L VZ. This was associated with the decrease in 11-KT level, suggesting direct VZ effects on testicular androgenesis and sperm functions. In goldfish exposed to 100 μg/L VZ, 11-KT was increased but E(2) remained unchanged. This is, probably, the main reason for unchanged sperm quality at 100 μg/L VZ. In goldfish exposed to E(2), GSI and 11-KT were decreased, E(2) was increased and no sperm was produced. The present study shows different dose-dependent VZ effects, which lead to impairment in sperm quality via disruption in steroidogenesis. In addition to VZ effects through competitive binding to AR, our data suggests potential effects of VZ by direct inhibition of 11-KT biosynthesis in fish as well as abnormalities in sperm morphology.

Cloning, pharmacological characterization and expression analysis of Atlantic cod (Gadus morhua, L.) nuclear progesterone receptor

To better understand the role(s) of progesterone in fish spermatogenesis, we cloned the nuclear progesterone receptor (Pgr) of Atlantic cod. The open-reading frame of the cod pgr consists of 2076 bp, coding for a 691-amino acids-long protein that shows the highest similarity with other piscine Pgr proteins. Functional characterization of the receptor expressed in mammalian cells revealed that the cod Pgr exhibited progesterone-specific, dose-dependent induction of reporter gene expression, with 17α,20β-dihydroxy-4-pregnen-3-one (DHP), a typical piscine progesterone, showing the highest potency in activating the receptor. During ontogenesis, the pgr mRNA was undetectable in embryo's 24 h after fertilization, but became detectable 4 days after fertilization. During the larval stage, the expression levels increased steadily with the development of the larvae. In adult fish, pgr was predominantly expressed in gonads of both sexes. During the onset of puberty, testicular pgr transcript levels started to increase during rapid spermatogonial proliferation, and peaked when spermiation started. In situ hybridization studies using testis tissue during the rapid growth phase containing all germ cell stages indicated that in cod, pgr mRNA is predominantly located in Sertoli cells that are in contact with proliferating spermatogonia. Taken together, our data suggests that the Pgr is involved in mediating progestagen stimulation of the mitotic expansion of spermatogonia, and in processes associated with the spermiation/spawning period in Atlantic cod.

Modulations in androgen and estrogen mediating genes and testicular response in male goldfish exposed to bisphenol A

Adverse effects of bisphenol A (BPA) on reproductive physiology were studied in male goldfish (Carassius auratus) exposed to nominal environmentally relevant concentrations (0.2 and 20 µg/L) for up to 90 d. Transcriptions of various reproductive genes were measured in brain, liver, and testis to investigate the BPA modes of action. Volume, density, total number, motility, and velocity of sperm were measured to assess testicular function. At 0.2 µg/L, BPA reduced steroidogenetic acute regulatory protein and increased estrogen receptors (ERs) messenger RNA (mRNA) transcript (ERβ1 in liver and ERβ2 in testis) after 90 d. At 20 µg/L, BPA increased mRNA transcript of androgen receptor in testis, brain- and testis-specific aromatase, and vitellogenin in liver after 90, 30, 60, and 60 d, respectively. Transcripts of ERs mRNA were increased after 30 to 60 d at 20 µg/L BPA; increase in ERβ1 mRNA was observed in testis after 7 d. Total number, volume, and motility of sperm were decreased in males exposed to 0.2 and 20 µg/L BPA, whereas sperm density and velocity were only reduced at 20 µg/L BPA. The results support the hypothesis that BPA may exert both anti-androgenic and estrogenic effects, depending on concentration, leading to diminished sperm quality. The findings provide a framework for better understanding of the mechanisms mediating adverse reproductive actions of BPA observed in different parts of the world.