贪吃的朋友 小心撑坏身体

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平时，贪吃的朋友们总是觉得多吃一点没有关系，满足自己的嘴馋最要紧。然而，你们知道吗？贪吃、吃得过多有可能会导致死亡。所以，大家还是要合理饮食。

建议大家多食蔬菜和水果。

Yael: Hey Don, do you know why over-eating can be lethal for a squid?

Don: Obese squid are prone to heart disease, Yael?

Y: No. In fact, it would only take a single oversized meal to kill or cause brain injury to a squid.

D: Brain injury? I'm stumped.

Y: Squid are part of a diverse group of highly evolved invertebrates called cephalopod mollusks. Cephalopods, which also include octopus and cuttlefish, have the largest and most complex brains of all the invertebrates. Like all invertebrates, squid don't have a bony skeleton. And squid even lack a hard outer shell like many other mollusks have. But squids' brains are protected by a capsule of flexible cartilage.

D: Yael, what does this have to do with over-eating?

Y: Oh right. Well, the squid's digestive system passes right through its brain!

D: Whaaaaat?

Y: Yep. Although the cartilage surrounding the brain is flexible, it doesn't stretch. However, the esophagus running through the middle of the brain does stretch. If a squid tried to swallow too large a piece of food, the esophagus would expand, squashing its brain into the sides of its head. But squid are well adapted to avoid this problem. They have hard chitinous beaks, sort of like parrots' beaks, that break up even hard-shelled food into manageable pieces. The food is further broken down by strong enzymes in their saliva, and a hard, raspy tongue-like structure called a radula. The radula is covered with rows of small sharp teeth specially adapted to grinding and shredding. So the squid's dinners are reduced to tiny particles before swallowing.

D: An esophagus through the brain! Who knew squid were so fascinating!?