英语听力文摘 English Digest 682 昆虫血为何是绿色或黄色（打印版）

You’ve probably heard someone use the phrase “blood red,” but have you ever wondered if all blood really is red? For example, think about the bugs you’ve seen splatter against your car’s windshield, leaving behind a clear, yellowish, or greenish liquid. That liquid, is hemolymph, or insect blood.

The blood of an insect functions differently than the blood of a human. In humans, blood gets its red color from hemoglobin, which travels through blood vessels carrying oxygen from the lungs to the rest of the body. Insect blood, however, does not carry gasses and has no hemoglobin. Instead, bugs have a system of tubes that transport gasses directly between their cells and the outside air.

In fact, insects don’t even have blood vessels. Instead there is a hollow space inside their external skeleton in which their blood oozes around. This cavity extends to the antennas, legs, and wing veins. The bug’s heart, a long tube that stretches the length of its body, pushes the blood from the rear end of the insect on forward. The bug may also have little hearts at the ends of its extremities to help move the blood along.

Pumping blood is a slow process: it takes about eight minutes for an insect’s blood to circulate completely. Like human blood, bug blood carries nutrients and hormones to the insect’s cells. The greenish or yellowish color of insect blood comes from the pigments of the plants the bug eats.

为什么虫血是绿色或黄色？

你可能听说过有人用“血红”这个短语，但你有没有想过，是否所有的血液都是红色的？例如，想想你看到的虫子溅到你的汽车挡风玻璃上，留下一种清澈、淡黄色或绿色的液体。这种液体是血淋巴或昆虫血。

昆虫血

昆虫的血液与人类的血液功能不同。在人类中，血液的红色来源于血红蛋白，血红蛋白通过血管将氧气从肺部输送到身体其他部位。然而，昆虫血液不携带气体，也没有血红蛋白。相反，昆虫有一个管道系统，可以在它们的细胞和外界空气之间直接输送气体。

事实上，昆虫甚至没有血管。相反，在它们的外部骨骼中有一个中空的空间，血液在其中渗出。这个空腔延伸到天线、腿和翼静脉。这只虫子的心脏是一根长长的管子，它伸展着身体的长度，将昆虫后端的血液向前推。这种虫子的四肢末端也可能有小心脏，以帮助血液流动。

颜料

抽血是一个缓慢的过程：昆虫的血液需要大约八分钟才能完全循环。与人类血液一样，虫子的血液将营养物质和激素输送到昆虫的细胞中。昆虫血液的绿色或黄色来自于昆虫所吃植物的色素。

英语听力文摘 English Digest 682 昆虫血为何是绿色或黄色（在线收听）