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人们普遍印象中的鱼都是灵巧而灵敏的
据《生活科学》4月3日报道，当小鱼仔刚从卵中孵化出来的时候，它们也是“步履蹒跚”地为了生存而进行着不懈努力。大约有99％的鱼类死亡都发生在幼鱼阶段。
只有当它们长大一些，一些鱼才能够更好地逃避捕食者的追赶。成年的鱼会利用“突破并滑行”的方法快速逃脱天敌的追赶。这种方法能让它们很快地加速并随后依靠滑动“逃之夭夭”。而对于很多鱼类来说，它们并不是天生就把握这种方法的。
体重太轻身材太小成阻碍？
长时间以来，科学家一直猜测，可能是由于体重太轻让这些小鱼仔在“突破”的阶段难以获得足够的动力。或许是它们的身形太小，导致水就像粘稠糖浆一样阻碍它们，让它们难以很好地“滑行”。
器官发育不全是真正原因！
但是，一项最新的研究结果却提出了不同的看法。这项以斑马鱼幼仔为对象的研究显示，小鱼的游泳技巧之所以糟糕是因为它们发育尚不完善的侧鳍和鱼鳔所导致的，它们不能保持身体水平。研究人员还表示，他们的这一研究结果可能还同样适用于其它种类的鱼。
这项研究的负责人、荷兰瓦罕宁恩大学的乌尔里克·穆勒表示，动力要素可以解释某些鱼仔不善于游泳的情况，但并不是所有情况都如此。而且，也不能用鱼体大小不同来解释它们滑行能力的差别。“很多小鱼孵化出来时，胸鳍还没有完全成形，而且所有的鱼孵化时都还没有形成鱼鳔。所以，它们可能会面临相似的不善于游泳的问题。”
报道说，4月3日穆勒已经将他的研究发现提交给了在坎特伯雷举行的实验生物学协会年度大会。
You might think fish were born swimmers. Not so, however.
When they hatch, fish larvae struggle to get around and to survive. Some 99 percent of all fish mortality occurs in the larval stage.
Only when they grow some do fish get better at escaping predators. Adults make quick getaways using a burst-and-coast method in which they gain a lot of speed quickly and then glide away. Many species don't have this skill at birth.
Scientists have long suspected that the lack of larval weight prevented the little ones from gaining enough momentum in the burst phase. And perhaps their very small size caused the water to act more like syrup against them, preventing a good coast.
But a new study of zebrafish larvae concludes it's their poorly developed side fins and ineffective swim bladder that holds them back. They simply can't keep their bodies horizontal. The finding might apply to other species, researchers say.
"Momentum can explain some of the poor swimming in larvae, but not all, and the difference in coasting ability cannot be explained by differences in body length either," said study leader Ulrike Muller of Wageningen University in The Netherlands. "Many fish larvae hatch without fully formed pectoral fins and all hatch without a swim bladder, so similar problems could occur for them."
Muller is presenting her findings today at the Society for Experimental Biology's Annual Main Meeting in Canterbury.