Carpizo-Ituarte E, Hadfield M G
Biol Bull. 1998 Feb;194(1):14-24. doi: 10.2307/1542509.
The serpulid polychaete Hydroides elegans is a common, cosmopolitan warm-water biofouling organism. Competent larvae of H. elegans metamorphose rapidly after induction by marine biofilms. Only 15 min after coming in contact with the metamorphic cue, larvae have completed secretion of the primary tube; secretion of the secondary, calcareous tube begins 1.5 h after the primary tube has been deposited. Metamorphosis is characterized by disappearance of the prototroch and differentiation of the tentacular crown in the head region, the collar and thoracic membrane in the thoracic region, and the pygidium at the tip of the abdomen. These morphogenetic events were used to gauge the responses of larvae to biofilms, as well as to the artificial inducers Cs+ and K+. A maximal metamorphic response to the two ions requires exposure to different concentrations and durations, i.e., a 3-h pulse of 10 mM CsCl, or a 24-h continuous exposure to 50 mM excess KCl. The metamorphic response to Cs+ or K+ is much slower than the response to biofilms, demonstrating that the tissues respond differently to artificial inducers. The differences in the kinetics of the responses to the natural and cationic inducers suggest that the induction mechanisms are not the same. When these artificial inducers were used, some, but not all, of the metamorphosed juveniles never attached to the substratum or secreted a primary tube, probably as a result of secondary effects of the ions on processes of tube formation. The exact mechanisms by which Cs+ and excess K+ induce metamorphosis are still unclear, although we assume, as do others, that these agents act by depolarizing the membranes of excitable sensory cells and not by interacting with specific receptors.
螺旋多毛纲动物优美盘管虫是一种常见的、分布于世界各地的暖水生物污损生物。优美盘管虫的 competent 幼虫在受到海洋生物膜诱导后会迅速变态。与变态线索接触仅15分钟后，幼虫就完成了初级管的分泌；在初级管沉积1.5小时后，次级钙质管的分泌开始。变态的特征是原纤毛轮消失，头部区域的触手冠、胸部区域的领部和胸膜以及腹部末端的尾节发生分化。这些形态发生事件被用来衡量幼虫对生物膜以及人工诱导剂Cs⁺和K⁺的反应。对这两种离子的最大变态反应需要暴露于不同的浓度和持续时间，即10 mM CsCl的3小时脉冲，或50 mM过量KCl的24小时连续暴露。对Cs⁺或K⁺的变态反应比对生物膜的反应慢得多，这表明组织对人工诱导剂的反应不同。对天然诱导剂和阳离子诱导剂反应动力学的差异表明诱导机制不同。当使用这些人工诱导剂时，一些（但不是全部）变态后的幼体从未附着在基质上或分泌初级管，这可能是离子对管形成过程产生次级效应的结果。Cs⁺和过量K⁺诱导变态的确切机制仍不清楚，尽管我们和其他人一样假设，这些试剂通过使可兴奋感觉细胞的膜去极化起作用，而不是通过与特定受体相互作用。
