网站首页 | 关于我们 | 英语论坛 | 广告合作 | 设为首页 | 收藏本站 热点资讯:Seoul steps up peace effort amid Pyongyan Xi urges enhanced capacity to fight disas
热搜: 英语作文  英语话剧  影视
当前位置: 首页 > 英语听力 > VOA >

科学家发现古代龙虾有心

2014-04-09 17:27[VOA] 来源: 浏览: 次 评论:

Scientists have discovered the world's earliest known cardiovascular system - heart and blood vessels - in the fossil of a shrimp-like creature from more than 500 million years ago. The rare find sheds new light on the evolutionary timeline of life on Earth.
   mp3下载
The Yunnan Province in southwestern China is known for rich fossil deposits, but researchers had not expected a fossil so exquisitely preserved as the specimen of the 520-million-year-old shrimp-like species.


The entire cardiovascular system in the Fuxianhuia protensa fossil. (Credit: Xiaoya Ma)

Researcher Peiyun Cong with the Yunnan Laboratory for Paleobiology unearthed the fossil, which gave researchers the first detailed image of the creature's circulatory system.

“[The fossil] is a beautiful carbon trace," said University of Arizona neuroscientist and team member Nicholas Strausfeld. "It is bilaterally symmetrical. It shows the dorsal blood vessel and the lateral vascular components, the arteries, the lateral arteries and then a very, very, beautiful, system of arteries over where the brain sits in the head.”

In earlier research with fossils of the same species, the scientists on this project had identified its brain, gut and nervous system.

Strausfeld says it is common to see fossils with imprints of teeth, shell and bone, but no soft tissues because they decay first when a creature dies. He explains how the internal organs may have fossilized.

“We assume that the specimens became entombed by a very sudden event - a sudden burial, maybe an underwater landslide, maybe something to do with a tsunami, who knows, maybe a very, very heavy dust fall out from a storm," he said. "And, then this chemical preservation of the internal tissue as it was squashed flat.”

This ancient marine species dates from the Cambrian period, a time in Earth’s history when major animal groups began to appear with a huge variety of shapes and forms. Strausfeld says the organ systems detailed in this study are easily recognizable in today's crustaceans.

“It suggests that already 520 million years ago, the basic layout, what we call the ground pattern, of say a vascular system, had already evolved," he said. "And the ground pattern persists until this day in modified forms.”

If we see this ancient shrimp as modern, then, Strausfeld asks, who was the ancestor that gave rise to its sophisticated and very elaborate set of organs?

“This is not going to be easy [to answer] because we do not really have access to any older deposits," Strausfeld said. "So what we hope to find in these Chengjiang deposits in China are fossils of organisms that clearly were already ancient by that time, and that might give us a lead into how these more elaborate systems, these very recognizable elaborate systems, how these systems maybe originated.”

【看这里~】

如果大家有兴趣的话,请关注【 英语巴士网-VOA 】栏目,英语巴士网整合了您可能感兴趣的相关英语学习资料,可以多看一下哦(^_^)

英语巴士公众号

欢迎扫描二维码关注英语巴士公众号!

(编辑:admin)

网友评论
热门标签