Ionic control of settlement and metamorphosis in the tadpole larvae of ascidian, Styela canopus Savigny
- 海洋环境－已发表论文 
研究了人工海水中三种金属离子K+,Mg2+和Ca2+分别在不同浓度下对冠瘤海鞘(Styelaca nopusSavigny)幼体附着和变态的影响,同时采用K+通道阻滞剂TEA检验其可兴奋细胞膜上的K+通道特性,对冠瘤海鞘幼体附着和变态的离子控制机制进行初步探讨,结果表明:K+的浓度为20~40mmol/dm3 时诱导幼体附着和变态的效果最佳,低于4 5mmol/dm3 和高于80mmol/dm3 的K+浓度都表现出抑制效果;Mg2+浓度在0 ~ 32 mmol/dm3 时显著促进幼体附着和变态,达88mmol/dm3时起抑制作用;在人工海水中无论添加或减少Ca2+,均有效抑制幼体变态.TEA不能阻抑增加K+的诱导作用,这表明冠瘤海鞘幼体可兴奋细胞膜上的K+通道对外部TEA不敏感.另外,人工海水中缺乏K+或Ca2+或K+浓度达80mmol/dm3 都会对冠瘤海鞘幼体产生毒害作用.The effects of changes in concentrations of potassium, magnesium and calcium on settlement and metamorphosis in the Styela canopus Savigny larvae in artifical seawater and the characteristic of the potassium channels in externally accessible, excitable cell membrane were studied. K~(+) effectively induced larval settlement and metamorphosis during the concentrations of 20~40 mmol/dm~3, but showed inhibitive effect in the concentrations being less than or egual to 4.5 mmol/dm~3 or being greater than or egual to 80 mmol/dm~3.The inductive effect of 0~32 mmol/dm~3 Mg~(2+) was remarkable, but 88 mmol/dm~3 Mg~(2+) inhibited larval settlement and metamorphosis. The settlement and metamorphosis of the larvae would be inhibited no matter whether increased or decreased Ca~(2+) in artificial seawater. The failure of inhibiting the inductive effect of K~(+) by a K~(+)-channel blocker TEA (tetraethylammonium chloride) indicated that the potassium channels in externally accessible, excitable cell membrane of Styela canopus Savigny larvae are insensitive to external TEA. Like 80 mmol/dm~3 K~(+), K~(+)-free or Mg~(2+)-free seawater would produce evidence of toxicity. The mechanisms of ionic control of settlement and metamorphosis in the Styela canopus Savigny larvae were discussed.