菊池氏細鯽Aphyocypris kikuchii(Oshima, 1919)人工繁養殖及幼苗發育

Induced Spawning and Larval Development of Aphyocypris kikuchii (Oshima, 1919)

菊池氏細鯽Aphyocypris kikuchii（Oshima, 1919）爲台灣特有種，主要分布於台灣的東部三縣，屬於小型淡水魚類，兼具生態與觀賞價值，由於近年來棲地的破壞及環境污染問題，使其族群分布範圍與數量逐漸減少，已逐漸成爲罕見魚種。本研究採用成熟雌雄種魚各10隻，以人工2次注射腦下垂體（10μg/gwt）與LRH-A（0.2μg/gwt）研磨液進行催熟，並藉由種魚自然繁殖產卵與育苗試驗，以了解菊池氏細鯽之生殖習性與魚苗發育過程，期望逐步建立菊池氏細鯽之繁殖與幼苗發育的基礎生物學資料，並應用於種原庫建立或自然環境中之復育。菊池氏細鯽主要將卵產於沈水植物直立部分與浮水植物的根部，魚卵卵徑約1.16mm，透明且光滑，沈性且帶黏性，在水溫25℃的環境中，受精卵發育至4 HAS （hours after spawning）進入原腸期（gastrula stage），約12 HAS可觀察到肌節（myotome），約13 HAS觀察到心跳，約29-30 HAS孵化，初孵化魚苗全長平均爲3.3mm，孵出第3天（days after hatch, DAH）可開始攝食餌料，13 DAH已可觀察到背鰭與臀鰭發育完整；19 DAH尾鰭發育完整；30 DAH可觀察到鱗片發育完整，此時與成魚的外表形態類似。

The Kikuchi minnow Aphyocypris kikuchii (Oshima, 1919) is a small native freshwater fish inhabiting in streams, ponds, and small lakes in the eastern Taiwan. Due to over-fishing for fishing bait and to environmental deterioration from water pollution and habitat destruction, its population has been gradually declining, so that it has become rare or extinct in many parts of its original range. In this study, the mature male and female fish were injected twice with a mixed solution of LRH-A (0.2 μg/g wt) and grounded pituitary glands of walking catfish (Clarias sp.) (10 μg/g wt). Their spawning, developments of embryos and larvae were observed at 25℃ in the laboratory. Fertilized eggs had an average diameter of 1.16 mm, developed to the gastrula stage around 4 HAS (hours after spawning) and to the formation of myotomes around 12 HAS. Heart started to beat at 13 HAS, and larvae hatched at 29-30 HAS. The yolk-sac larvae had an average total length of 3.3 mm and started to ingest food on 3 DAH (days after hatching). The dorsal and anal fins were well developed on 13 DAH, tail fin on 19 DAH, and scales on 30 DAH.