Mahardini Angka, Yamauchi Chihiro, Takeuchi Yuki, Rizky Dinda, Takekata Hiroki, Takemura Akihiro
Graduate School of Engineering and Sciences, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.
Gen Comp Endocrinol. 2018 Dec 1;269:112-121. doi: 10.1016/j.ygcen.2018.09.001. Epub 2018 Sep 3.
Food availability can become a factor driving the reproductive activity of tropical fish, particularly when primary production within their habitats fluctuates with tropical monsoons. The present study examined the involvement of insulin-like growth factors (IGF) in controlling the reproduction of the sapphire devil Chrysiptera cyanea, a reef-associated damselfish that is capable of manipulating its reproductive activity based on food availability. We cloned and characterized the cDNAs of igf1 and igf2 and determined their transcript levels in relation to seasonal and food-manipulated reproduction. The partial cDNAs of sapphire devil igf1 and igf2 had open reading frames (ORFs) composed of 600 bp (155 amino acid residue) and 636 bp (211 aa), respectively. Phylogenetic analyses revealed that IGF1 and IGF2 of the sapphire devil were clustered into those of teleosts. The gonadosomatic index increased from March to June. Vitellogenic oocytes and ovulatory follicles were observed in ovaries from May to June, which suggests that the spawning season lasts for at least 2 months. The hepatosomatic index, but not the condition factor, increased in March and June. The transcript levels of igf1 in the brain, but not in the liver, increased in April, June (vitellogenesis) and July (post vitellogenesis). Ovarian activity during the spawning season was maintained by high food supply (HH) for 30 days, although it was suppressed in the food-restriction treatment (LL) and restored in the re-feeding treatment (LH). The transcript levels of igfs in the brain, but not in the liver, in LH were lower than those in HH and LL. Moreover, immersing fish in seawater containing estradiol-17β suppressed transcript levels of igfs in the liver, but not in the brain. We conclude that reproductive activity during the spawning season is influenced by nutritive conditions and that crosstalk exists between the reproductive and growth network in the neural and peripheral tissues, thus controlling the reproductive activity of this species.
食物可利用性可能成为驱动热带鱼繁殖活动的一个因素，尤其是当它们栖息地内的初级生产力随热带季风波动时。本研究考察了胰岛素样生长因子（IGF）在控制蓝宝石雀鲷（Chrysiptera cyanea）繁殖中的作用，蓝宝石雀鲷是一种与珊瑚礁相关的雀鲷，能够根据食物可利用性来调节其繁殖活动。我们克隆并鉴定了igf1和igf2的cDNA，并确定了它们与季节性繁殖和食物调控繁殖相关的转录水平。蓝宝石雀鲷igf1和igf2的部分cDNA分别具有由600 bp（155个氨基酸残基）和636 bp（211个氨基酸）组成的开放阅读框（ORF）。系统发育分析表明，蓝宝石雀鲷的IGF1和IGF2聚类到硬骨鱼类的相应分支中。性腺指数从3月到6月增加。5月至6月在卵巢中观察到卵黄生成卵母细胞和排卵卵泡，这表明产卵季节至少持续2个月。肝体指数在3月和6月增加，但条件因子没有增加。4月、6月（卵黄生成期）和7月（卵黄生成后期），大脑中igf1的转录水平增加，而肝脏中的转录水平没有增加。产卵季节的卵巢活动通过高食物供应（HH）维持30天，尽管在食物限制处理（LL）中受到抑制，在重新投喂处理（LH）中恢复。LH组大脑中igfs的转录水平低于HH组和LL组，而肝脏中的转录水平没有差异。此外，将鱼浸泡在含有17β-雌二醇的海水中会抑制肝脏中igfs的转录水平，但不会抑制大脑中的转录水平。我们得出结论，产卵季节的繁殖活动受营养条件影响，并且神经和外周组织中的生殖网络与生长网络之间存在相互作用，从而控制该物种的繁殖活动。
