Abstract
Simple SummaryCultured 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.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.
Highlights
The order Acipenseriformes comprises 27 species, with natural distribution in Eurasia and North America [1]
The dysfunction is overcome by the injection of gonadotropins [carp pituitary suspension (CP), chorionic gonadotropins], to supplement production of endogenous luteinizing hormone (LH) [5]
The discovery of gonadotropin-releasing hormone (GnRH) [6] and its effects introduced a new tool for regulating reproduction in cultured fish [7]
Summary
The order Acipenseriformes comprises 27 species, with natural distribution in Eurasia and North America [1]. Artificial environments lacking natural spawning stimuli do not induce appropriate endogenous responses from the fish [3], and cultured sturgeon often manifest reproductive dysfunction at the final level of gametogenesis [4]. The dysfunction is overcome by the injection of gonadotropins [carp pituitary suspension (CP), chorionic gonadotropins], to supplement production of endogenous luteinizing hormone (LH) [5]. The discovery of gonadotropin-releasing hormone (GnRH) [6] and its effects introduced a new tool for regulating reproduction in cultured fish [7]. Subsequent production of GnRH analogues (GnRHa) with modified amino acid positions has resulted in multiple increase of GnRHa effectiveness in stimulating LH secretion and ovulation [8]
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