Miranda L A, Strüssmann C A, Somoza G M
Laboratorio de Ictiofisiología y Acuicultura, Instituto de Investigaciones Biotecnológicas-Instituto Tecnológico de Chascomús, B7130IWA Chascomus, Buenos Aires, Argentina.
Fish Physiol Biochem. 2009 Mar;35(1):101-8. doi: 10.1007/s10695-008-9232-3. Epub 2008 May 27.
In this study we examined the endocrine mediation between environmental factors (temperature and photoperiod) and the brain-pituitary-gonadal axis in females of pejerrey Odontesthes bonariensis. Changes in the expression of brain gonadotropin-releasing hormones (GnRHs) and gonadotropin (GtH) subunit [follicle stimulating-beta (FSH-beta), luteinizing hormone-beta (LH-beta), glycoprotein hormone-alpha (GPH-alpha)] genes, plasma gonadal steroids [estradiol (E(2)) and testosterone (T)], gonadal histology, and gonadosomatic index (GSI) in adult females exposed to combinations of short-day (8 h) or long-day (16 h) photoperiods and low (12 degrees C) or high (20 degrees C) temperatures after winter conditions (8 h light, 12 degrees C) were analyzed. Pejerrey females kept under the short photoperiod had low GSIs, and their ovaries contained only previtellogenic oocytes regardless of the experimental temperature. In contrast, females exposed to the long photoperiod had high GSIs and ovaries with vitellogenic oocytes at both temperatures. These fish also showed a significantly higher expression of sGnRH, pjGnRH, cGnRH-II (the three different GnRH variants found to date in the pejerrey brain), FSH-beta, LH-beta and GPH-alpha genes and plasma E(2 )levels than those at the shorter photoperiod. No significant changes were observed in plasma T levels. Based on these results, we concluded that the increase in day length but not that of temperature triggers the maturation of pejerrey females after the winter period of gonadal rest and that this occurs by an integrated stimulation of the various components of the brain-pituitary-gonad axis.
在本研究中，我们检测了环境因素（温度和光周期）与佩氏南美无须鳕（Odontesthes bonariensis）雌鱼脑-垂体-性腺轴之间的内分泌调节作用。分析了经历冬季条件（8小时光照，12摄氏度）后，暴露于短日照（8小时）或长日照（16小时）光周期与低温（12摄氏度）或高温（20摄氏度）组合条件下的成年雌鱼，其脑促性腺激素释放激素（GnRHs）和促性腺激素（GtH）亚基[促卵泡激素-β（FSH-β）、促黄体生成素-β（LH-β）、糖蛋白激素-α（GPH-α）]基因的表达变化、血浆性腺类固醇[雌二醇（E₂）和睾酮（T）]、性腺组织学以及性腺指数（GSI）。处于短光周期下的佩氏南美无须鳕雌鱼的GSI较低，无论实验温度如何，其卵巢仅含有卵黄生成前的卵母细胞。相比之下，处于长光周期下的雌鱼在两种温度下的GSI均较高，且卵巢中含有卵黄生成期的卵母细胞。这些鱼还显示，与短光周期下的鱼相比，其sGnRH、pjGnRH、cGnRH-II（迄今为止在佩氏南美无须鳕脑中发现的三种不同GnRH变体）、FSH-β、LH-β和GPH-α基因的表达以及血浆E₂水平显著更高。血浆T水平未观察到显著变化。基于这些结果，我们得出结论，日照时长的增加而非温度的升高触发了佩氏南美无须鳕雌鱼在性腺休止的冬季过后的性腺成熟，且这一过程是通过对脑-垂体-性腺轴各组成部分的综合刺激而发生的。
