OSMOREGULATORY MECHANISMS DURING EARLY LIFE STAGES IN FISH

本研究以全盐罗非鱼（Oreochromis mossambicus）和鲑鱼（Oncorhynchus keta）为研究对象，旨在阐明鱼类生命早期的渗透调节机制，并探讨卵黄囊膜中氯细胞参与渗透调节的可能性。以下是过去两年的研究结果：大马哈鱼眼期胚胎具有低渗调节能力，胚胎后期卵黄囊膜上的氯离子细胞可能代替鳃氯离子细胞参与盐挤出。同样，在罗非鱼胚胎中，卵黄囊膜中的氯细胞是海水中离子交换的潜在重要位点。在罗非鱼中，皮质醇处理刺激了体内和体外胚胎和幼虫的卵黄囊膜中氯细胞的大小和数量，表明蛋黄中存在的皮质醇可能参与了生命早期阶段的渗透调节。

The present study was undertaken to clarify the osmoregulatory mechanisms during early life stages in fish and to investigate the possible involvement of chloride cells in the yolk-sac membrane in osmoregulation, using euryhaline tilapia (Oreochromis mossambicus) and chum salmon (Oncorhynchus keta). The followings are the results obtained for the last two years :1.Eyed-stage embryos of chum salmon possess hypoosmoregulatory ability and chloride cells in the yolk-sac membrane may be involved in salt extrusion, in place of gill chloride cells, during the late embryonic stages.2.Similarly, in tilapia embryos, chloride cells in the yolk-sac membrane are potentially important sites for ion exchange in seawater.3.In tilapia, cortisol treatment stimulates the size and number of chloride cells in the yolk-sac membrane of embryos and larvae in vivo and in vitro, suggesting that cortisol present in the yolk may be involved in osmoregulation during early life stages.