has bushy gills to extract oxygen from the current. 并依靠浓密的鳃从水中过滤氧气

30. have to hang on for dear life.
    得有办法固定自己以保住性命
31. Invertebrates dominate these upper reaches.
    无脊椎动物统治着上游河段
32. The hellgrammite, its body flattened to reduce drag,
    这是鱼蛉 其扁平的身体 能减少水的冲击力
33. has bushy gills to extract oxygen from the current.
    并依靠浓密的鳃从水中过滤氧气
34. Black fly larvae anchor themselves with the ring of hooks,
    蚋的幼虫靠钩环固定自己
35. but if these become unstuck,
    即使不小心松脱了
36. they're still held by a silicon safety line.
    它们还有一根坚韧的“安全索”

来自《行星地球 第一季 第三集 Planet Earth S01E03 淡水》第 33 行