OSMOREGULATORY MECHANISMS DURING EARLY LIFE STAGES IN FISH

点击翻译按钮获取中文摘要

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.