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,20ß-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,20ß-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.

Hormonal induction of ovulation using Ovaprim™ [(D-Arg6, Pro9NEt)-sGnRH+domperidone] and its impact on embryonic development of wild-caught Longspine scraper, Capoeta trutta (Heckel, 1843).

Knowledge of gamete quality is a prerequisite for developing techniques to fertilize eggs and rear offspring for hatchery production. Our objective was to develop assisted reproductive techniques, via hormonal induction of final oocyte maturation (FOM), for Longspine scraper, Capoeta trutta. Fish were administered injections of salmon gonadotropin-releasing hormone analogue containing anti-dopaminergic drug (Ovaprim™) or saline (control). Effects of Ovaprim on induction of ovulation, gamete quality, embryonic development, and larval survival were later examined with serum steroid hormone levels and ovarian histology. The saline group failed to spawn, whereas Ovaprim accelerated FOM and induced spawning. Fish treated with Ovaprim showed an increase in gonadosomatic index, egg diameter, and wet weight relative to controls. Average absolute fecundity, relative fecundity, fertilization, and hatching rates were 8823 eggs/spawn, 53 eggs/g body weight, 95%, and 91%, respectively. Serum 17α,20ß-dihydroxy-4-pregnen-3-one (DHP) levels were significantly enhanced by ∼4-fold in Ovaprim-treated fish compared to the saline-injected fish, while 17ß-estradiol levels declined upon FOM in hormone treated fish. Embryonic development closely resembled the teleost scheme, despite variations in timing. Larval survival at 6 and 12days post-hatch were 98% and 95%, respectively. Results suggest that Ovaprim is efficient for inducing spawning in C. trutta for stock enhancement or hatchery purposes.

Steroidogenic acute regulatory protein transcript abundance in the eel, Anguilla australis: changes during the induced reproductive cycle and effects of follicle-stimulating hormone during previtellogenesis.

Steroidogenic acute regulatory protein (StAR) mRNA levels in the eel ovary were assayed by quantitative PCR and related to plasma steroid levels throughout oogenesis in order to shed light on the previously considered 'aberrant' prematurational increase in plasma levels of estradiol-17ß (E2). Total ovarian StAR transcript abundance mirrored circulating levels of E2, but not of 11-ketotestosterone (11KT). The study was complemented by evaluation of in vitro effects of follicle-stimulating hormone (FSH) on ovarian StAR transcript abundance and on short-term ('acute') radiolabelled pregnenolone-supported steroid metabolism by ovarian fragments to understand how the production of steroids during previtellogenic oocyte growth is regulated. We observed a significant effect of FSH on StAR mRNA levels within 24h of incubation, but these were no longer evident by 4 days of culture. Unexpectedly, FSH had no effect on substrate-supported steroidogenesis, as comparable yields of steroid products were detected using semi-quantitative HPLC and scintillation counting. We conclude that the eel ovarian follicle can respond to FSH from a very early stage of development (early oil droplet stage) by increasing StAR mRNA levels, but that there is no evidence for acute effects of FSH on bioactive steroid production downstream of cytochrome P450 side-chain cleavage. Furthermore, the prematurational increase in StAR mRNA in vivo is in keeping with general teleost models and is likely to be a 'normal' response to reaching advanced stages of development.