Invertebrates dominate these upper reaches. The hellgrammite, its body flattened to reduce drag, has bushy gills to extract oxygen from the current. Black fly larvae anchor themselves with the ring of hooks, but if these become unstuck, they're still held by a silken safety line. There are advantages to life in the fast stream - bamboo shrimps can just sit and sift out passing particles with their fan-like forearms. Usually, these mountain streams only provide enough food for small animals to survive. But with the spring melt here in Japan monsters stir in their dens. Giant salamanders, world's largest amphibian, almost two metres long. They're the only large predator in these icy waters. They begin their hunt at night. These salamanders have an exceptionally slow metabolism. Living up to 80 years they grow into giants.


这里以无脊椎动物为主，角鱼蛉身体扁平，这样可以减少水的冲力，它还长有灌木一样的鳃，便于吸收水流中的氧气。蚋蝇幼虫凭借附肢上的钩环把自己锚定在水里。即使这样坚持不住，它们还有像丝一样的安全带。在急流中生活自有它的好处。竹节虾只需等在那里，用它扇子一样的前臂过滤那些路过者。 通常山间溪流里的食物只能供小动物生存，但在日本的这一地区，春天融化了冰雪，洞穴里的那些大动物蠢蠢欲动了。这是隐鳃鲵，它们是世界上最大的两栖动物，身长达两米。它们是这片冰冷水域中唯一的大型食肉动物。它们通常晚上出来觅食。它们的寿命可达80年，身体长得很大。