美国科学家：鲨鱼第六感觉与人类基因有联系

美国科学家：鲨鱼第六感觉与人类基因有联系 Sharks#39; Sixth Sense Related to Human Genes 摘要：The same genes that give sharks their sixth sense and allow them to detect electrical signals are also responsible for the development of head and facial features in humans, a new study suggests. 美国科学家的一项最新研究显示，使鲨鱼具有第六感并让它们能够电流信号的基因对人类头部和面部特征的发育也起着重要作用。 The same genes that give sharks their sixth sense and allow them to detect electrical signals are also responsible for the development of head and facial features in humans, a new study suggests. The finding supports the idea that the early sea creatures which eventually evolved into humans could also sense electricity before they emerged onto land. The study, led by Martin Cohn and his lab at the University of Florida, is detailed in the current issue of the journal Evolution & Development. Sharks have a network of special cells that can detect electricity, called electroreceptors, in their heads. They use them for hunting and navigation. This sense is so developed that sharks can find fish hiding under sand by honing in on the weak electrical signals emitted by their twitching muscles. The researchers examined embryos of the lesser spotted catshark. Using molecular tests, they found two independent genetic markers of neural crest cells in the sharks#39; electroreceptors. Neural crest cells are embryonic cells that pinch off early in development to form a variety of structures. In humans, these cells contribute to the formation of facial bones and teeth, among other things. The finding suggests that neural crest cells migrate from the sharks#39; brains to various regions of the head, where they develop into electroreceptors. Glenn Northcutt, a neuroscientist at the University of California, San Diego, who was not involved in the study, said the finding was interesting, but that more studies are needed before a direct link between neural crest cells and electroreceptors can be established. "It still requires a definitive experiment, where the developing neural crest cells are marked with dye, the embryo develops and the dye clearly shows up in the electroreceptors," Northcutt said. In the new study, the researchers found snippets of genetic material associated with neural crest cells in the electroreceptors. They did not dye the neural crest cells and trace their development. Scientists think that all primitive animals with backbones, including the early ancestors of humans, could sense electricity. As they evolved, mammals, reptiles, birds and most fish lost the ability. Today, only sharks and a few other marine species, such as sturgeons and lampreys, can sense electricity. "Our fishy ancestors had the anatomy for it," said study team member James Albert, a biologist from the University of Louisiana. The ability to sense electrical signals is useful in aquatic environments because water is so conductive. On land, however, the sense is useless. "Air doesn#39;t conduct electricity as well," Albert said. "When it happens, it#39;s called a lightning bolt and you don#39;t need special receptors to sense it." The development of the electroreceptors is believed to mirror the development of the lateral line, a sense organ in fish that allows them to detect motion in surrounding water. Similar processes are thought also to be involved in the development of the inner ear, the organs which help humans keep their balance. The electroceptors are also believed to behind many sharks#39; ability to detect changes in the Earth#39;s magnetic field. Other studies indicate that like sailors, sharks can also navigate by celestial cues. 美国科学家的一项最新研究显示，使鲨鱼具有第六感并让它们能够检测电流信号的基因对人类头部和面部特征的发育也起着重要作用。 据“生活科学”2月7日报道，这一发现支持了此前的一个观点，即最终进化为人类的早期海洋生物在它们尚未开始陆地生活之前，也能够探测到水中的电流信号。 鲨鱼头部有个能探测到电流的特殊细胞网状系统，被称为电感受器。鲨鱼就利用电感受器来捕食猎物及在水中自由游弋。美国研究人员对小斑点猫鲨的胚胎进行了研究。通过分子测试，他们在鲨鱼的电感受器中发现了神经嵴细胞的两种独立基因标志。神经嵴细胞是胚胎发育早期形成各种组织的胚胎细胞。人类的神经嵴细胞对人面部骨骼和牙齿的形成起重要作用。这一发现说明，神经嵴细胞从鲨鱼的脑部移至其头部的各个区域，并在其头部发育为电感受器。 美国其他一些研究者认为这个发现非常有意思，但是要想在鲨鱼神经嵴细胞与电感受器之间建立直接联系，还需要进行更多的研究。这项研究是由美国佛罗里达大学的马丁·科恩和其实验室负责完成的，具体研究结果被发表在日前出版的《进化与发展》杂志上。 科学家认为所有的原始脊椎动物，包括人类早期祖先在内都具有电流感受能力。但随着它们的进化，乳动物、爬行动物、鸟类和大部分鱼类都丧失了这种能力。现在，只剩下鲨鱼和其它一些海洋生物，如鲟鱼和七鳃鳗等还仍旧保留着这种“超能力”。 对此，研究成员之一、路易斯安娜大学的生物学家詹姆斯·阿伯特说：“我们的鱼类祖先就拥有这样的生理结构。”研究人员还表示，这种可以探测电流的能力在有水的环境下具有非常重要的作用，但是在陆地上，它就不起什么作用了。