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你知道水母眼睛在哪儿吗?

蝌蚪五线谱 2018-07-31

  腔肠动物的眼睛至少曾出现过8次独立进化,其中就包括了水母。这一发现有助于阐明这些动物是如何进化并产生这样复杂的视觉器官的。

  来自加州大学圣塔芭芭拉分校的生态、进化和海洋生物学系教授Todd Oakley解释道:“眼睛是科学家们所研究的最复杂的器官之一。虽然其它拥有复杂神经系统的动物们也曾不止一次地进化过眼睛,但相对而言,腔肠动物的神经系统的复杂程度要低得多,因此这一生物的眼睛进化了很多次的事实着实令人惊讶。”

  图片来源:David Liittschwager/UC Santa Barbara

  研究人员收集了数量庞大的遗传数据,从中推断出腔肠动物种类之间的关系。其研究成果发表在《当代生物学》杂志上。

  眼睛探测光线并将其转化为神经元中的电化学脉冲。这个过程是复杂生命体中的视觉功能的先驱。然而,一些简单的生物,如水母,也有许多种类的眼睛,它们与苍蝇和人类等动物一样,使用同样的光感受蛋白,即视蛋白。

  研究人员将他们的遗传数据与广泛的文献搜索结合在一起,梳理出腔肠动物中感光视蛋白的历史性表达。

  在之前的研究中,Oakley的实验室发现,视蛋白被腔肠动物用在眼外来触发激活螫刺细胞,即刺囊细胞。

  该研究表明,在这些无眼的水母中不仅存在广泛的光感应行为,而且这一组复杂的、带有透镜的眼睛与其它类型的眼睛也有着不同的来历。

  “在我们现已囊括的腔肠动物的物种数量中,可以发现眼睛的起源现象出现了很多次,”来自奥克利进化研究室的研究生,同时也是该研究的第一作者Natasha Picciani解释道,“形态学细节和视蛋白不同,这便能支撑眼睛是独自进化的理论。而我们的研究表明,简单的构建块可以用不同的方式构建出复杂的东西。”

  这些发现证明了趋同进化的概念:造成不同血统物种相似特征的独立起源。

  趋同进化——同样也发生在植物中——创造出类似形式或功能的结构,却不存在于该物种群组中的最后一个共同祖先中。

 

责任编辑:sun

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