UNESP - Universidade Estadual Paulista - Centro de Aquicultura, Jaboticabal, SP, Brazil.
Institute of Marine Biology, Biotechnology and Aquaculture, Hellenic Center for Marine Research, Heraklion, Crete, Greece.
Gen Comp Endocrinol. 2019 Aug 1;279:120-128. doi: 10.1016/j.ygcen.2019.02.016. Epub 2019 Feb 12.
Lambari-do-rabo-amarelo Astyanax altiparanae in the wild reproduce during spring and summer, but females undergo vitellogenesis throughout the year, including the non-spawning winter period when water temperatures are low. The present study investigated the physiological role of temperature modulation on the hypothalamus-pituitary-gonads axis of lambari during winter, as well as the effects of gonadotropin releasing hormone agonist (GnRHa) therapy. Captive females were exposed to two different temperatures (20 °C and 27 °C) and were injected weekly with GnRHa for 21 days during winter (Control, CTR; Low dose; LD and high dose of GnRHa, HD). At the end of the 21-days period gonadosomatic index (GSI), oocyte stage of development and theoretical fecundity were evaluated, together with plasma levels of 17β-estradiol (E). Gene expression of the two pituitary gonadotropins follicle-stimulating hormone (fshβ) and luteinizing hormone (lhβ), as well as hepatic vitellogenin-A (vtgA) expression were also analyzed. At the end of the experimental period, females from the six different experimental conditions were induced to spawn using human chorionic gonadotropin (hCG). Spawning performance parameters and plasma levels of the maturation inducing steroid (MIS) were analyzed. Gene expression of fshβ did not change with temperature manipulation, but females exposed to 27 °C and supplemented with a HD of GnRHa exhibited an increased fshβ gene expression, associated with higher E levels. The higher water temperature alone was able to increase E levels. At both water temperatures GnRHa injections induced a decrease in E levels. GnRHa injected females had a lower vtgA gene expression levels at 20 °C. Even with differences in the gene expression of gonadotropins among the various temperature/GnRHa treatments, GSI and oocyte diameter did not change, but GnRHa enhanced the number of vitellogenic oocytes at 20 °C. The reproductive performance of lambari induced to spawn with hCG was better after the combined treatment with GnRHa and summer temperature.
黄尾副拟铲颌鱼在野外繁殖期为春季和夏季，但雌性在全年都进行卵黄生成，包括水温较低的非繁殖冬季。本研究调查了温度调节对冬季黄尾副拟铲颌鱼下丘脑-垂体-性腺轴的生理作用，以及促性腺激素释放激素激动剂（GnRHa）治疗的影响。将圈养的雌性暴露于两种不同的温度（20°C 和 27°C），并在冬季每周注射 GnRHa 21 天（对照，CTR；低剂量；LD 和高剂量 GnRHa，HD）。在 21 天的时间结束时，评估了性腺指数（GSI）、卵母细胞发育阶段和理论繁殖力，以及血浆中 17β-雌二醇（E）的水平。还分析了两种垂体促性腺激素滤泡刺激素（fshβ）和促黄体生成素（lhβ）以及肝卵黄蛋白原-A（vtgA）表达的基因表达。在实验结束时，使用人绒毛膜促性腺激素（hCG）诱导来自六个不同实验条件的雌性产卵。分析产卵性能参数和成熟诱导类固醇（MIS）的血浆水平。fshβ 的基因表达不受温度操作的影响，但暴露于 27°C 并补充高剂量 GnRHa 的雌性显示 fshβ 基因表达增加，与更高的 E 水平相关。单独较高的水温能够增加 E 水平。在两种水温下，GnRHa 注射均降低了 E 水平。在 20°C 时，GnRHa 注射的雌性 vtgA 基因表达水平较低。即使在各种温度/GnRHa 处理之间存在促性腺激素基因表达的差异，GSI 和卵母细胞直径也没有改变，但 GnRHa 增强了 20°C 时卵黄生成卵母细胞的数量。与 GnRHa 和夏季温度联合处理后，用 hCG 诱导产卵的黄尾副拟铲颌鱼的繁殖性能更好。
