Gonadotropin Induced Synchronous Changes of Morphology and Gonadal Development in the Japanese Eel Anguilla japonica

促性腺激素誘發日本鰻形態與生殖腺發育的同步化改變

韓玉山(Yu-San Han) ； 曾萬年(Wann-Nian Tzeng) ； 廖一久(I-Chiu Liao)

《臺灣水產學會刊》 33卷4期 (2006/12) Pp. 333-343

https://doi.org/10.29822/JFST.200612.0004

摘要

先前的研究中已證實，野生日本鰻在銀化過程中形態上的改變與生殖腺的發育呈現同步化現象。在本研究中，吾人擬探討促性腺激素是否扮演關鍵的角色。將高屏溪採補到之日本鰻的黃鰻每週施打人類絨毛膜促性腺激素(HCG)，檢驗樣本在形態上的改變與生殖腺的發育模式。經過五週的施打後(0.75 IU/克體重)，根據鰻魚體色的變化將其分為反應良好組與反應不良組。大約有50%的雄鰻與20%的雌鰻反應良好，變態為銀鰻。反應良好組其平均年齡、體長、體重、肥滿度、性腺指數(GSI)、胸鰭指數(FI)、肝指數(HSI)以及眼徑指數(OI)皆顯著高於反應不良組。相反地，消化道指數(DSI)在反應良好組則顯著低於反應不良組。性腺指數與眼徑指數呈現正相關，而與消化道指數呈現負相關。發育程度較佳之鰻魚對促性腺激素之反應較為敏感，而在促性腺激素施打後，鰻魚體色、眼徑指數與消化道指數之變化與性腺之發育呈現同步化現象，顯示，腦下垂體－性腺軸在日本鰻銀化過程中扮演重要的角色。

關鍵字

日本鰻 ； 銀化 ； 性腺發育 ； 形態 ； 人類絨毛膜促性腺激素

並列摘要

In a previous study, we had observed synchronous changes of morphology and gonadal development in wild Japanese eel during the silvering process. In this study, we aimed to clarify if gonadotropin is the key hormone responsible for this phenomenon. Yellow eels captured in the Kaoping River were repeatedly injected with human chorionic gonadotropin (HCG), and changes of morphology and gonadal development were examined. After five weekly injection of HCG at a dosage of 0.75 IU/g body weight, eels was classified into well-responsive and poor-responsive groups according to skin coloration. Approximately 50 % of males and 20 % of females were responsive to become silver eels. Mean age, total length, body weight, condition factor, gonadosomatic index (GSI), fin-index (FI), hepatosomatic index (HSI) and ocular index (OI) were significantly higher in well-responsive eels than in poorresponsive eels. In contrast, the mean digestosomatic index (DSI) significantly decreased in wellresponsive eels. OI was positively correlated and DSI was negatively correlated with the GSI in both sexes. These results indicated that well developed eels are more sensitive to HCG treatment, and the skin color, eye size, gonadal development and digestive tract shrinkage were synchronous after HCG injection. The pituitary-gonad axis plays important role on eel silvering.

並列關鍵字

Japanese eel ； Silvering ； Gonadal development ； Morphology ； Human chorionic gonadotropin