Ovaprim, a commercial spawning inducer, stimulates gonadotropin subunit gene transcriptional activity: A study correlated with plasma steroid profile, ovulation and fertilization in the catfish Heteropneustes fossilis

Effects of thyroxin and luteinizing hormone releasing hormone on reproductive physiology of Rohu (Labeo rohita): Insights into spawning performance, oocyte maturation, steroidogenesis, and follicular development genes

As the global aquaculture industry grows, attention is increasingly turning towards assisted reproductive technologies. In this study, we examined the impact of D-Ala6, Pro9-Net-mGnRH (LHRHa: 0.4 mL/kg) and two doses (1 and 10 μg/kg fish) of thyroxin (T4) administered through a single injection on oocyte maturation, spawning performance, sex steroid hormone levels, as well as the expression of genes related to steroidogenesis and follicle development (ZP2, Cyp19a1a and SF-1) in Rohu (Labeo rohita). The study found that untreated female Rohu did not spawn, while those treated with LHRHa and thyroxin ovulated and spawned across a hormonal gradient. The highest spawning success was observed with a thyroxin dosage of 10 µg/kg (no significant change with a dose of 1 μg/kg), and female latency period decreased with increasing dosage. Additionally, females treated with thyroxin exhibited significantly higher fecundity than other experimental groups. Treatment with LHRHa and two doses of thyroxin significantly increased the gonadal somatic index compared to the control and sham groups. Hormonal treatment also led to increased fertilization success, hatching rate, and larval survival. At 12 h post-injection, females treated with thyroxin exhibited a significant decline in estradiol levels and expression of Zp2, Cyp19a1a, and SF-1 compared to other experimental groups. Levels of DHP significantly increased across the hormonal gradient. Histological analyses supported a steroidogenic shift, where oocyte maturation was accelerated by hormone administration, particularly with both doses of thyroxin. In conclusion, the findings suggest that thyroxin is a recommended treatment for assisted reproduction of Rohu due to its ability to induce spawning, increase fecundity and improve larval survival.

A novel technique for mass induction of propagation in small fish species: Hormone immersion

Due to the lack of environmental stimuli found in their natural habitat, not all species of tiny fish can reproduce naturally in the conditions of captivity. Silver rasbora (Rasbora argyrotaenia) was used as the model organism in this study, which is the first to successfully use the hormonal technique of immersion to mass induce spawning and spermiation in small fish species. In this study, in order to find out the effect of immersion hormone treatment, two separate experiments in which commercial hormone Ovaprim™ was used for spawning induction and Ovagold™ for spermiation induction were conducted. Four doses of hormones (0.0 mL/L, 0.7 mL/L, 1.4 mL/L, and 2.1 mL/L) were evaluated on 24 females and 40 males in total. According to the experimental findings of female breeders, 1.4 mL/L dose of Ovaprim™ showed best results on latency period (8.67 h) with a total number of eggs (6994 egg) and fertilization rate (99.22 %). In addition, hatching and larval survival rate have also increased. Milt volume and sperm concentration have also seen an increase to 4.25 μL/g bw and 42.71 10⁶ cell/μL respectively at 2.1 mL/L hormone concentration. The best results or responses were obtained by immersion treatments using Ovaprim™ doses of 1.4 mL/L on female and Ovagold™ concentrations of 2.1 mL/L on male. This new technique is a beneficial for breeding small fish species for either commercial or conservational culture condition.

Manipulation of the Tyrosinase gene permits improved CRISPR/Cas editing and neural imaging in cichlid fish

Direct tests of gene function have historically been performed in a limited number of model organisms. The CRISPR/Cas system is species-agnostic, offering the ability to manipulate genes in a range of models, enabling insights into evolution, development, and physiology. Astatotilapia burtoni, a cichlid fish from the rivers and shoreline around Lake Tanganyika, has been extensively studied in the laboratory to understand evolution and the neural control of behavior. Here we develop protocols for the creation of CRISPR-edited cichlids and create a broadly useful mutant line. By manipulating the Tyrosinase gene, which is necessary for eumelanin pigment production, we describe a fast and reliable approach to quantify and optimize gene editing efficiency. Tyrosinase mutants also remove a major obstruction to imaging, enabling visualization of subdermal structures and fluorophores in situ. These protocols will facilitate broad application of CRISPR/Cas9 to studies of cichlids as well as other non-traditional model aquatic species.

Artificial Reproduction of Blue Bream (Ballerus ballerus L.) as a Conservative Method under Controlled Conditions

Simple Summary

Quite severe biological imbalances have been caused by the often ill-conceived and destructive actions of humans. The natural environment, with its flora and fauna, has been subjected to a strong, direct or indirect, anthropogenic impact. In consequence, the total population of wild animals has been considerably reduced, despite efforts to compensate for these errors and expand the scope of animal legal protection to include endangered species. Many animal populations on the verge of extinction have been saved. These actions are ongoing and embrace endangered species as well as those which may be threatened with extinction in the near future as a result of climate change. The changes affect economically valuable species and those of low value, whose populations are still relatively strong and stable. Pre-emptive protective actions and developing methods for the reproduction and rearing of rare species may ensure their survival when the ecological balance is upset. The blue bream is one such species which should be protected while there is still time.

Abstract

The blue bream Ballerus ballerus (L.) is one of two species of the Ballerus genus occurring in Europe. The biotechnology for its reproduction under controlled conditions needs to be developed to conserve its local populations. Therefore, a range of experiments were performed to obtain valuable gametes from blue bream following hormonal stimulation with carp pituitary homogenate (CPH), Ovopel and Ovaprim. CPH and Ovopel were injected twice and Ovaprim—once, under a pectoral fin. The spawners were inspected 12 h after the last injection, and the gametes were collected. Eggs were collected from spawning females and fertilized with sperm from three males. The smallest number of ovulating blue bream (four females) was obtained from individuals stimulated with Ovaprim. There were six to nine ovulating females in the other groups, accounting for 60–90% of the females in the respective groups. The latency period was the shortest in the spawners stimulated with Ovopel. The fish in this group ovulated 14 h after the hormonal injection. Spawning was synchronized and all females spawned simultaneously. The highest average weight of eggs per fish (75.4 g) was obtained from the females stimulated with Ovopel, whereas the individuals stimulated with Ovaprim provided the smallest average amount of eggs (49.5 g). The study showed that blue bream spawners are not very sensitive to reproduction-related handling under controlled conditions.

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.

Spawning performance, serum sex steroids, and ovarian histology in wild-caught Levantine scraper, Capoeta damascina (Valenciennes, 1842) treated with various doses of sGnRHa + domperidone

As global aquaculture continues to expand, increasing efforts are focusing on assisted reproductive technologies. This study sought to test whether salmon GnRH [D-Arg6, Pro9NEt]) analogue (sGnRHa) + domperidone injection at 0.25 mL/body weight (BW; 5-μg sGnRHa + 2.5-mg domperidone), 0.5 mL/kg BW (10-μg sGnRHa + 5-mg domperidone), or 1.0 mL/kg BW (20-μg sGnRHa + 10-mg domperidone) affects spawning performance and gamete quality in wild-caught Levantine scraper, Capoeta damascina. The ability of these treatments to elicit a response was further examined by in vivo stimulation of estradiol (E2) and 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and by its in vivo potency to induce oocyte maturation (OM). Females that received saline injection (control) did not spawn, whereas sGnRHa + domperidone induced ovulation and spawning across the hormonal gradient. Spawning success was highest with the 0.5 mL/kg dosage (80%) and female latency period decreased with increasing dosage. Females treated with 0.5 mL/kg had a significantly higher fecundity than those injected with 0.25 or 1.0 mL/kg. Mean oocyte diameter significantly increased in females treated with 0.5 or 1.0 mL/kg. Fertilization success, hatching rate, larvae morphology, and survival were not affected by hormonal treatment. At 12 h postinjection, E2 levels significantly declined in females treated with 0.5 or 1.0 mL/kg, whereas DHP levels significantly increased across the hormonal gradient. This steroidogenic shift is supported by histological analyses, where OM was accelerated by administration of sGnRHa + domperidone in a dose-dependent manner. In conclusion, the 0.5 mL/kg dosage of sGnRHa + domperidone is recommended for assisted reproduction of Levantine scraper.

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.

Reproductive stage- and sex-dependant effects of neurohypophyseal nonapeptides on gonadotropin subunit mRNA expression in the catfish Heteropneustes fossilis: An in vitro study

In the present study, in vitro effects of synthetic vasotocin (VT), isotocin (4Ser, 8Ile- oxytocin; ITb) and the recently cloned IT gene paralog product (8Val-Isotocin, ITa) were studied on the expression of pituitary gonadotropin (GtH) subunit mRNA levels. In male pituitaries of early (preparatory phase) and late (prespawning phase) recrudescing catfish, Heteropneustes fossilis, VT (10 nM, 100 nM and 1000 nM) stimulated fshβ expression dose-dependently. But in females, the dose-dependent effect was found only in the preparatory phase. In males, VT stimulated lhβ expression only at higher doses. In females, VT produced a significant dose-dependent increase of the lhβ expression only in the prespawning phase. VT stimulated the expression of gpα, dose-dependently in the preparatory phase in males and in the prespawning phase in females. The incubation of the pituitaries with ITb did not alter the fshβ expression in either sex in both preparatory and prespawning phases. In males, ITb stimulated the expression of lhβ and gpα only at the highest concentration (1000 nM) in both phases. In females, ITb stimulated both lhβ and gpα expression only at 1000 nM in the preparatory phase and dose-dependently in the prespawning phase. The incubation of the pituitaries with ITa produced effects similar to ITb on the expression of fshβ, lhβ, and gpα. The results show that the basic peptide VT modulates both fshβ and lhβ expressions, which are influenced by the sex and reproductive stage. The neutral peptide ITA/ITb exerts an insignificant effect on the fshβ expression regardless of sex or season. Both VT and ITa/ITb elicit a significant effect on the lhβ expression in late recrudescent phase especially in females.