Cephalopod belongs to an important economic mollusk and also plays an important role in the marine ecological system. 摘要头足类不仅是重要的经济软体动物，同时在海洋生态系中扮演着重要的角色。
If the species of the original system have been lost or invaders have appeared, the former pristine conditions may never be regained. 如果原本生态系中的物种消失了，或有外来物种入侵，这个生态系可能永远无法回复原貌。
