Scary, squishy, cool, brainless, mesmerizing -- jellyfish are all of these and a whole lot more. Anatomically they're relatively simple animals; they lack not just brains, but also blood and bones, and possess only rudimentary sense organs. Despite their name, jellyfish aren't, of course, fish. In fact they aren't any one thing.
可怕、黏糊、酷炫、无脑、迷人--水母综合了所有这些特点，而且远不只如此。从身体构造来看，它们是相对简单的动物；它们不只没有脑，也没有血液和骨骼，只有基本的感觉器官。水母的英文是jellyfish，尽管如此，它们并不是鱼。事实上，水母在分类学上无法分类成单一群体。
Many of the creatures lumped together as jellyfish are no more closely related than, say, horseflies are to horses. Not only do they occupy disparate branches of the animal family tree, but they also live in different habitats; some like the ocean surface, others the depths, and a few prefer freshwater. What unites them is that they've converged on a similarly successful strategy for floating through life: Their bodies are gelatinous.
许多被笼统归类成水母的动物，它们之间的亲缘关系其实就跟马蝇和马一样，并不密切。它们不但在动物系谱树里占据不同的分支，也生活在不同的栖地里：有些喜欢海洋表面，有些喜欢深海，少数偏好淡水。这些动物的共同点，是它们都趋同演化出类似且成功的漂浮式生命策略：它们都有胶质状的身体。
Not surprisingly, given their diverse evolutionary history, jellies exhibit a fantastic range of shapes, sizes, and behaviors. When it comes to reproduction, they're some of the most versatile creatures on the planet. Jellyfish can produce offspring both sexually and asexually; depending on the species, they may be able to create copies of themselves by dividing in two, or laying down little pods of cells, or spinning off tiny snowflake-shaped clones in a process known as strobilation. Most astonishing of all, some jellies seem able to reproduce from beyond the grave.
可以想见，由于水母的演化史各异，它们也呈现出形形色色的外形、大小和行为。在繁殖方面，它们可以说是地球上最多才多艺的生物。水母可以行有性生殖与无性生殖；按物种不同，有的可以一分为二变出另外一个自己、有的会在水里产下精子或卵子，有的能透过称为断裂生殖的过程，释放出许多微小的、雪花状的无性繁殖系。最令人惊讶的是，有些水母似乎在死后还可以繁殖。
The so-called immortal jellyfish resembles a tiny, hairy thimble and lives in the Mediterranean Sea and also off Japan. Members of the species can reverse the aging process so that instead of expiring, they reconstitute themselves as juveniles. The juvenile then starts the jellyfish's life cycle all over again. It's as if a frog, say, were to revert to a tadpole or a butterfly to a caterpillar. Scientists call the near-miraculous process transdifferentiation.
有永生水母之称的灯塔水母，看起来就像是毛茸茸的迷你顶针，生活在地中海与日本沿海。这种水母可以逆转老化过程，因此不会死亡，反而能返老还童，回到幼体期，重新开始生命周期。这就好比一只青蛙重新变成蝌蚪，或是蝴蝶重新回到毛毛虫的阶段。科学家将这种堪称奇迹的过程称为转分化。
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