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Voa02 lesson 31-60, (38) Sea Creature Sees Without Eyes

(38) Sea Creature Sees Without Eyes

Sea Creature Sees Without Eyes

A relative of starfish does not have eyes, but can still see. That information comes from scientists who studied sea creatures in the coral reefs of the Caribbean and Gulf of Mexico.

The researchers reported this month that the starfish relative -- called the red brittle star -- is only the second creature known to be able to see without having eyes. This ability is called extraocular vision.

The other creature said to have extraocular vision is a kind of sea urchin.

Brittle stars, with five arms extending from a central disk, are part of a group of marine life called echinoderms. They have a nervous system but no brain.

The red brittle star measures up to about 35 centimeters wide, from the end of one arm to the other. It lives in bright and complex environments. Because of the possibility of being eaten by fish, the creature hides during daylight hours.

The red brittle star possesses extraocular vision as a result of light-sensing cells, called photoreceptors. These photoreceptors cover its body and chromatophores, the cells responsible for pigment or coloring.

During daytime, the chromatophores narrow the field of light being detected, making each photoreceptor like the pixel of a computer image. When combined with other pixels, the image becomes complete.

The visual system does not work at night, when the chromatophores contract in size.

Laboratory experiments suggested that the brittle stars have very simple vision. Placed in a circular environment, for example, they moved toward walls that were white with a black bar, suggestive of a daytime hiding place.

Lauren Sumner-Rooney is a research fellow at the Oxford University Museum of Natural History. She led the study, which appeared in the publication Current Biology.

“If our conclusions about the chromatophores are correct, this is a beautiful example of innovation in evolution,” she said.

Sumner-Rooney added, “It's such an alien concept for us, as very visually driven animals, to conceive of how an animal might see its habitat without eyes, but now we know of two examples.”


(38) Sea Creature Sees Without Eyes

Sea Creature Sees Without Eyes

A relative of starfish does not have eyes, but can still see. That information comes from scientists who studied sea creatures in the coral reefs of the Caribbean and Gulf of Mexico.

The researchers reported this month that the starfish relative -- called the red brittle star -- is only the second creature known to be able to see without having eyes. This ability is called extraocular vision.

The other creature said to have extraocular vision is a kind of sea urchin.

Brittle stars, with five arms extending from a central disk, are part of a group of marine life called echinoderms. 海蛇尾有五个从中央圆盘延伸出来的手臂,是一组称为棘皮动物的海洋生物的一部分。 They have a nervous system but no brain.

The red brittle star measures up to about 35 centimeters wide, from the end of one arm to the other. It lives in bright and complex environments. 它生活在明亮而复杂的环境中。 Because of the possibility of being eaten by fish, the creature hides during daylight hours. 由于可能被鱼吃掉,这种生物在白天隐藏。

The red brittle star possesses extraocular vision as a result of light-sensing cells, called photoreceptors. These photoreceptors cover its body and chromatophores, the cells responsible for pigment or coloring. 这些光感受器覆盖了它的身体和色素细胞,这些细胞负责色素或着色。

During daytime, the chromatophores narrow the field of light being detected, making each photoreceptor like the pixel of a computer image. 在白天,色素细胞缩小了被检测的光场,使每个感光器就像计算机图像的像素。 When combined with other pixels, the image becomes complete. 当与其他像素组合时,图像变得完整。

The visual system does not work at night, when the chromatophores contract in size. 当色素细胞体积收缩时,视觉系统在夜间无法工作。

Laboratory experiments suggested that the brittle stars have very simple vision. 实验室实验表明,海蛇尾的视觉非常简单。 Placed in a circular environment, for example, they moved toward walls that were white with a black bar, suggestive of a daytime hiding place. 例如,放置在圆形环境中时,它们会移向带有黑色条的白色墙壁,暗示着白天的藏身之处。

Lauren Sumner-Rooney is a research fellow at the Oxford University Museum of Natural History. Lauren Sumner-Rooney 是牛津大学自然历史博物馆的研究员。 She led the study, which appeared in the publication Current Biology. 她领导了这项研究,该研究发表在《当代生物学》杂志上。

“If our conclusions about the chromatophores are correct, this is a beautiful example of innovation in evolution,” she said. “如果我们关于色素细胞的结论是正确的,这是进化创新的一个很好的例子,”她说。

Sumner-Rooney added, “It's such an alien concept for us, as very visually driven animals, to conceive of how an animal might see its habitat without eyes, but now we know of two examples.” Sumner-Rooney 补充说:“对于我们作为视觉驱动的动物来说,想象一个动物如何在没有眼睛的情况下看到它的栖息地,这是一个非常陌生的概念,但现在我们知道了两个例子。”