乌龟壳是怎么长出来的?日本科学家揭开新秘密
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日本科学家揭开了一个新秘密:乌龟壳是怎么长出来的。
据英国广播公司报道,乌龟的肋骨是如何朝外长、然后融合成一体形成一个包在体外的坚硬的壳呢?日本一组研究人员通过对乌龟胚胎的发育过程进行了研究。
研究结果刊登在最新一期美国的《科学》杂志上。
日本研究人员将乌龟、鸡和鼠的胚胎加以对比。之后发现,随着乌龟胚胎的发育,其体壁的一部份开始向内折叠,迫使肋骨向外长。
科学家说,体壁向内折叠的结果是,“背甲盘”----也就是乌龟皮肤深层加厚----的产生,这决定了以后龟壳的外置。
研究人员发现,乌龟、鸡和鼠的胚胎早期发育模式基本相同,肌肉、骨骼位置大体相仿。
随着胚胎的发育,乌龟体壁"向内折叠"这个现象强行阻止肋骨朝内长、将肩胛骨固定在与其他动物相似的位置,这等于给乌龟的体态重新划了一张设计图。
日本研究人员说,现代乌龟的发育过程中,在肋骨还没有完全把肩胛骨包起来的时候,乌龟的形态和这个远古化石很相近。
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