Effects of hCG and salmon gonadoliberine analogue on spermiation in the Eurasian perch ( Perca fluviatilis )

Paternal-effect-genes revealed through sperm cryopreservation in Perca fluviatilis

Knowledge about paternal-effect-genes (PEGs) (genes whose expression in the progeny is influenced by paternal factors present in the sperm) in fish is very limited. To explore this issue, we used milt cryopreservation as a specific challenge test for sperm cells, thus enabling selection amidst cryo-sensitivity. We created two groups of Eurasian perch (Perca fluviatilis) as a model - eggs fertilized either with fresh (Fresh group) or cryopreserved (Cryo group) milt from the same male followed by phenotypic-transcriptomic examination of consequences of cryopreservation in obtained progeny (at larval stages). Most of the phenotypical observations were similar in both groups, except the final weight which was higher in the Cryo group. Milt cryopreservation appeared to act as a "positive selection" factor, upregulating most PEGs in the Cryo group. Transcriptomic profile of freshly hatched larvae sourced genes involved in the development of visual perception and we identified them as PEGs. Consequently, larvae from the Cryo group exhibited enhanced eyesight, potentially contributing to more efficient foraging and weight gain compared to the Fresh group. This study unveils, for the first time, the significant influence of the paternal genome on the development of the visual system in fish, highlighting pde6g, opn1lw1, and rbp4l as novel PEGs.

Constant darkness negatively affects the outcome of hormonally induced reproduction in cultured Eurasian perch females

This study aimed to assess the effect of constant darkness applied to fish during controlled breeding on reproductive traits in domesticated females of Eurasian perch. Based on the assumption that keeping fish in constant darkness during the reproduction operation may reduce stress, suspected to be responsible for variable spawning effectiveness in this species. Two conditions were assessed (16 h light per day [group 16L] and constant darkness [group 0L], two tank replicates per condition). The reproductive protocol involved a 7-day-long adaptation period for group 0L where photoperiod was reduced by 2.3 h a day down to constant darkness. After the adaptation period, two hormone injections (salmon gonadoliberin analogue) were applied to both groups: priming (10 µg/kg) and resolving (25 µg/kg) with a 7-day interval between them. During the study, morphometric indices were recorded and blood, brain, and pituitary samples were collected to assess stress markers and determine hypothalamic-pituitary-gonadal axis functioning via measuring blood plasma hormones, as well as gonadoliberin and gonadotropins (luteinising hormone [LH] and follicle-stimulating hormone [FSH]) transcript abundance (n = 7 for each group at each sampling point). In addition, kinetics of the final oocyte maturation (FOM) process, ovulation rate, and egg quality of each group was monitored (n = 12 for each group). The results indicated that there were no differences in terms of morphometry, FOM kinetics, and most stress indices between groups throughout the experiment, except haematocrit, which increased immediately following the acclimation period in fish kept in darkness. Constant darkness negatively affected plasma levels of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and LH transcript expression at the time of the second hormone injection. This indicated that exposure to constant darkness negatively affected priming of the hormonal dose applied, resulted in the disruption of ovulation, and reduced ovulation rates (50%) for group 0L, as compared to 16L (91%). The findings of this study clearly indicate that constant darkness may have significant deleterious effects on reproductive traits throughout out-of-season induced, hormonally supported, controlled reproduction. Therefore, we advise against the use of constant darkness when managing broodstock reproduction in domesticated Eurasian perch.

Repeated hormonal induction of spermiation affects the stress but not the immune response in pikeperch (Sander lucioperca)

Hormonal induction of spermiation, previously reported to be immunogenic in fishes, is a common hatchery practice in pikeperch, Sander lucioperca. The aim of the present study was to investigate the effects of repeated induction of spermiation in pikeperch, following application of either human chorionic gonadotropin (hCG) or salmon gonadoliberine analogue (sGnRHa) on sperm quality indices as well as on immune and stress response. Mature males of pikeperch (n = 7 per group) were stimulated twice with five days between injections of either hCG (hCG; 500 IU kg^-1), sGnRHa (sGnRHa; 50 μg kg^-1) or NaCl (control group; 1 ml kg^-1) to assess spermatozoa motility with a computer-assisted sperm analysis (CASA) system. During second sampling, blood plasma was sampled for humoral innate immune (peroxidase and lysozyme activities, ACH50), stress (cortisol, glucose) and endocrine (testosterone) markers. In addition, the head kidney was dissected to assay the expression of several immune genes (such as il1, c3, hamp, tnf-α and lys genes). The results indicate that hormonal treatment significantly increased sperm production. Sperm sampled after the hormonal treatment maintained its quality throughout the study, regardless of the sampling time. However, it appears that the application of hCG induced elevated cortisol and glucose plasma levels compared to the control group. Almost all immune markers, except the relative expression of hepcidin (hamp gene), were unaffected by the two hormones applied. The results showed that the induction treatment of spermiation processes in pikeperch resulted in an important physiological stress response for which the intensity varied according to the hormonal agent used. However, this stress response (more profound following application of hCG) was weakly associated with innate immune functions. On the other hand, a significant negative correlation between the expression of several important immune markers (peroxidase activity, relative expression of c3 and il1 genes) and sperm quality indices indicates significant involvement of immune status on sperm quality. The results obtained shed light on immune-system-induced modifications to sperm quality. The data presented here highlight the need for careful revision of broodstock management and selection practices where welfare status as well as individual predispositions of fish to cope with the stress should be taken under the consideration.

The systematic development and optimization of large-scale sperm cryopreservation in northern pike (Esox lucius)

In our study, a systematic development of a new large-scale sperm cryopreservation protocol was carried out in northern pike (Esox lucius). The effect of 2 sugar based (glucose and trehalose) extenders, 3 dilution ratios (1:3, 1:9 and 1:19) 2 vol straws (0.5 and 5 mL) and a 10 mL cryotube, 2 different cryopreservation methods (Polystyrene box-P. box and Controlled Rate Freezer-CRF), as well as 3 different thawing periods (3, 3.5 and 4 min) were investigated on the motility of thawed sperm. The glucose based extender showed significantly higher pMOT (1:3-18 ± 16%, 1:9-20 ± 13%, 1:19-16 ± 12%) at all dilution ratios than in the trehalose based extender (1:3-0.3 ± 1%, 1:9-1±1%, 1:19-4±2%). A similar tendency was recorded in VCL and STR at a ratio 1:3 and 1:9. No significant difference was measured in sperm movement between the P. box and CRF using the 0.5 mL straw. Similarly no significant difference was observed in all motility parameters with 10 mL cryotube frozen in CRF at a ratio 1:3-1:19. An effective and short thawing period (3 min) was experimentally specified for the 10 mL cryotube cryopreserved in the CRF. In all large-scale cryopreservation methods, high pMOT (straw CRF: 57 ± 10%, straw P. box: 50 ± 9%, cryotube CRF: 41 ± 10%), and STR were measured, and no significant difference was recorded in all motility parameters. Our results demonstrate the effectiveness of our newly developed extender and the applicability of 3 different large-scale cryopreservation methods in pike sperm. Our protocols could be new prospective candidates for future exploitation in hatchery practice.

Rln3a is a prerequisite for spermatogenesis and fertility in male fish

The essential roles of Relaxin3 (RLN3) in energy homeostasis had been well investigated, while the mechanisms of RLN3 regulating reproduction remain to be elusive in mammals. Although two rln3 paralogues have been characterized in several teleosts, their functions still remain largely unknown. In this study, two paralogous rln3 genes, represented as rln3a and rln3b, were identified from the testis of Nile tilapia (Oreochromis niloticus). Rln3a was dominantly expressed in testis, while the most abundant rln3b expression was in brain. In situ hybridization demonstrated that rln3a is abundantly expressed in the Leydig cells of the testis. To understand the role of Rln3 in the testicular development, homologous null-rln3a gene mutant line was constructed by CRISPR/Cas9 technology. Morphological observation demonstrated that null mutation of rln3a gene caused testicular hypertrophy and a significant increase of GSI. However, a significant decrease of spermatogenic cells at different phases, i.e. spermatogonia, spermatocytes, spermatids and sperms was found. Silencing of rln3a gene repressed the expression of key genes in germ cell and Leydig cell. Deficiency of Rln3a led to the significant decrease of 11-KT production, which stimulated the up-regulation of both FSH and LH production in the pituitary via a negative feedback manner possibly. Mutation of rln3a in XY fish led to the hypogonadism with sperm deformation, significant decrease of fertility, and sperm motility, revealing as the high mortality of the offspring obtained by crossing the wild type female and rln3a^-/- XY fish. Interestingly, recombinant human RLN3 injection significantly enhanced the sperm motility in rln3a^-/- XY fish. Moreover, hCG treatment stimulated the expression of steroidogenic enzyme genes and 11-KT production, which were repressed by rln3a mutation in XY fish. Taken together, this study, for the first time by using a gene knockout model, proved that Rln3a is an indispensable mediator for androgen production in testis via HPG axis, and plays an essential role in spermatogenesis, sperm motility and male fertility in fish.

Effect of different treatment agents and post-treatment latency times on spermiation stimulation of northern pike (Esox lucius) under controlled conditions

The effect of different treatment agents, namely, carp pituitary homogenate (CPH), Ovaprim ([D-Arg⁶, Pro⁹NEt]-sGnRH + domperidone) and a dopamine-receptor antagonist (metoclopramide), on the stimulation of northern pike (Esox lucius) spermiation was tested under controlled conditions. To carry out the experiment, males (n = 84) were divided into four groups: control (n = 21); CPH (n = 21); Ovaprim (n = 21); metoclopramide (n = 21). The control group was given 0.9% NaCl but no hormonal treatment. After 24 h, sperm was collected from seven males belonging to control (n = 7), CPH (n = 7), Ovaprim (n = 7) and metoclopramide (n = 7). This procedure was repeated after 48 and 72 h post-treatment. At each time, sperm was collected from seven males from each group only once. After collection, the quantity and quality of sperm were determined. It was confirmed that the treatment agent and latency time (the time between treatment and sperm collection) are two factors affecting the quantity and quality of northern pike sperm collected under controlled conditions. The highest total sperm volume and total sperm production (TSP) were noted in the CPH group compared to the Ovaprim, metoclopramide and control groups. In contrast, the time of sperm collection affected the sperm concentration (SC), TSP and sperm pH. With increasing time, SC and TSP decreased, which indicated the occurrence of sperm hydration being part of the final sperm maturation process. Sperm maturation is in turn a consequence of increases in sperm pH and seminal plasma osmotic pressure between 48 and 72 h post-treatment. Sperm motility and sperm kinetic parameters were affected by treatment agent and the time of sperm collection. This indicates that the sperm's ability to move that is achieved in the optimal environment (in spermatic ducts) is dependent on both factors which determine sperm maturation in northern pike under controlled condition.

Testicular collections as a technique to increase milt availability in sauger (sander canadensis)

This study was conducted to compare quality and quantity of sperm collected from sauger (S. canadensis) using two collection methods: stripping alone and testicular tissue collection combined with stripping. Sperm were collected from sauger broodstock (n = 20) during the breeding season. Fish were randomly assigned to two sperm collection groups: (1) stripping once or (2) stripping twice before testicular tissue collection for obtaining additional sperm. Sperm motility variables, morphology, total number produced, and fertilization (%) were compared using the two collection methods. Testicular sperm had greater total motility (70.1 ± 2.1% compared with 44.3 ± 5.7%) but there were fewer morphologically normal cells (76.4 ± 1.3% compared with 92.8 ± 1.0%) compared to sperm collected using the stripping procedure. Sperm collection regimen utilizing testicular collections and sperm extractions in combination with stripping resulted in a ∼ten fold increase in total number of motile and morphologically normal sperm (39.5 ± 4.1 × 10 ⁹) compared with the currently utilized two sequential sperm stripping collection procedures alone (3.6 ± 4.1 × 10 ⁹ sperm). In large-scale studies (150,000 eggs), fertilization, using sperm collected from testicular tissues (1.0 × 10⁵ motile sperm/egg), was similar to sperm collected with only the stripping procedure (71.2 ± 5.5 %, 81.2 ± 5.5 %, P = 0.265). The results of this study indicate testicular collection combined with sperm extractions allows for collection of sperm of a quantity and quality to maximize fry production and reduce the problems with lack of broodstock availability for sperm collection.

Optimal treatment for spermatogenesis in male patients with hypogonadotropic hypogonadism

BACKGROUND

To compare the efficacies of gonadotropin-releasing hormone (GnRH) pulse subcutaneous infusion with combined human chorionic gonadotropin and human menopausal gonadotropin (HCG/HMG) intramuscular injection have been performed to treat male hypogonadotropic hypogonadism (HH) spermatogenesis.

METHODS

In total, 220 idiopathic/isolated HH patients were divided into the GnRH pulse therapy and HCG/HMG combined treatment groups (n = 103 and n = 117, respectively). The luteinizing hormone and follicle-stimulating hormone levels were monitored in the groups for the 1st week and monthly, as were the serum total testosterone level, testicular volume and spermatogenesis rate in monthly follow-up sessions.

RESULTS

In the GnRH group and HCG/HMG group, the testosterone level and testicular volume at the 6-month follow-up session were significantly higher than were those before treatment. There were 62 patients (62/117, 52.99%) in the GnRH group and 26 patients in the HCG/HMG (26/103, 25.24%) group who produced sperm following treatment. The GnRH group (6.2 ± 3.8 months) had a shorter sperm initial time than did the HCG/HMG group (10.9 ± 3.5 months). The testosterone levels in the GnRH and HCG/HMG groups were 9.8 ± 3.3 nmol/L and 14.8 ± 8.8 nmol/L, respectively.

CONCLUSION

The GnRH pulse subcutaneous infusion successfully treated male patients with HH, leading to earlier sperm production than that in the HCG/HMG-treated patients. GnRH pulse subcutaneous infusion is a preferred method.

Induction of spermiation using Ovaprim™ with topical gill method in the silver rasbora (Rasbora argyrotaenia)

The main obstacles on silver rasbora (Rasbora argyrotaenia) culture are having the limited number of broodstock and spawning depending on the season. The purpose of this study was to determine the effect of different dosage of Ovaprim™ induction by topical gill method to silver rasbora spermiation in order to continue the production out of its reproduction season with an optimum dose. A total of 30 male fish with a weight of 7.78 ± 0.20 g and length 4.11 ± 0.31 cm was used in this research. Topical gill treatments of Ovaprim™ were administered with following doses; 0.15 μl/g, 0.25 μl/g, 0.35 μl/g, 0.45 μl/g and 0.55 μl/g body weight. Milt volume, sperm concentration, sperm motility, and sperm viability parameters were observed in this study to understand the optimum dose of Ovaprim™ for male silver rasbora breeders. Spermiation induction of silver rasbora using Ovaprim™ with topical gill method has been successfully carried out, indicating an increase (P < 0.05) in milt volume, sperm concentration, sperm motility, and sperm viability. According to results a dose of Ovaprim™ is recommended to be used the 0.25 μl/g body weight in the spermiation induction of silver rasbora.

The comparison of two different extenders for the improvement of large-scale sperm cryopreservation in common carp (Cyprinus carpio)

In our study, a traditionally used (Grayling, already used in cyprinid species) and a newly tested (Pike) extender was tested to avoid sperm agglutination phenomenon following thawing during carp sperm cryopreservation. A large-scale (elevated volume of sperm) freezing method in a controlled-rate freezer using 5 ml straw and 10 ml cryotube was also systematically established. In all experiments, the sperm cryopreserved in using Grayling extender (except only one sample) showed an agglutination phenomenon (damaged and intact cells adhered to each other) after thawing where Pike extender resulted the regular cell suspension. No significant difference was observed between the two cryopreserved groups (Pike and Grayling extender) in all motility parameters using the 0.5 ml straw and the polystyrene box. Similarly, motility parameters did not show a significant difference in the two frozen groups with the 5 ml straw, also in the polystyrene box. A significantly higher progressive motility (pMOT, Grayling: 54% ± 8%, Pike: 37% ± 5%), straight line velocity (VSL, Grayling: 50 ± 5 µm/s, Pike: 39 ± 4 µm/s) and beat cross frequency (BCF, Grayling: 20 ± 1 Hz, Pike: 17 ± 1 Hz) was observed in the case of the grayling extender by the 5 ml straw cryopreserved in a controlled-rate freezer (CRF) compare to the pike extender. A significantly higher VSL (Grayling: 45 ± 3 µm/s, Pike: 38 ± 4 µm/s) was observed by the grayling extender using the 10 ml cryotube than with the pike extender. Despite the randomly occurring differences in a few parameters, our new controlled freezing method using the newly tested Pike extender, the 5 ml straw or the 10 ml cryotube can be a good solution for the preservation of elevated volume of carp sperm.

Effect of urine contamination on semen quality variables in Eurasian perch Perca fluviatilis L

The objectives of the present study were to determine values for semen quality variables in the Eurasian perch (i.e., osmolality of seminal plasma as well as sperm motility characteristics analyzed with CASA system) in response to (1) the method of milt collection (stripping or catheterization) and (2) experimental contamination of catheterized semen with urine (0%, 5%, 10%, 20%, 30% and 50% of contamination). Additionally, the effect of short-term chilled storage of experimentally contaminated semen (during the 24 h post semen collection period) on motility characteristics was investigated. Use of a typical stripping procedure resulted in about 5%-10% contamination of semen with urine, what is much less compared with other species. Markedly lesser values of straight line velocity (VSL) and consequently less linearity of spermatozoa movement (LIN) in perch semen, however, occurred as a result of stripping (46 ± 4 μm/s and 38 ± 4% for VSL and LIN, respectively), when compared to sperm collected by catheterization (87 ± 5 μm/s and 77 ± 2% for VSL and LIN, respectively), indicate that even a 10% contamination of semen with urine may have negative effects on quality. Exposure of semen to urine resulted in a significant dose-dependent decrease in the percentage of motile spermatozoa (MOT) and both velocity variables (VSL and VCL). Amount of urine contamination also affected MOT, VCL, VSL and LIN value during short-term storage. In conclusion, it is important to avoid semen contamination by urine when using the stripping procedure in the Eurasian perch, either for controlled reproduction or sperm preservation.

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.