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为什么吃木头的动物不太多

Why Don't More Animals Eat Wood?

Hi, this is Julián from MinuteEarth.
大家好 我是《分钟地球》的Julian
Make sure you stick around to the very end of the video
请务必坚持到视频的最后
to see a fun new thing we’re trying!
看看我们正在创作的新内容
On average, wood contains around 10 times more calories per kilogram
一般来讲 木头每千克所含热量
than fruit or leaves.
比水果或树叶多10倍左右
Yet while animals across the animal kingdom eat almost every part of trees:
虽然整个动物群几乎吃遍了树木的每一部分:
leaves, fruits, flowers, seeds, heck even their internal fluids,
叶子 果实 花 种子 茎甚至体内液体
the wood is almost exclusively eaten by a few insects.
而木头几乎只被一些昆虫吃掉
What’s keeping all those other animals from dining on,
是什么阻止其他动物在餐桌上用餐呢
well, the dining table?
难道是木质餐桌吗?
While wood is made up of the same nutritious carbohydrate called cellulose
木头的主要成分是一种叫纤维素的碳水化合物
that makes up of other tasty tree parts
它构成了树木其他的部分
Most of the cellulose in wood is bound together
木材中的大部分纤维素是由
by a complex molecule called lignin.
复杂分子“木质素”结合在一起的
This makes wood super strong on both the molecular level and the macro level,
这使得木材在分子层面和宏观层面都具有极高的硬度
so wood is hard to eat because it’s literally hard.
所以木头难吃的原因是因为它实在太硬了
Some animals, like beavers, have the right masticating machinery,
有些动物 比如海狸具有合适的咀嚼机制
like sharp teeth and strong jaws,
像锋利的牙齿和强壮的下颚
to break wood down on the macro-level,
能分解木头的表面部分
which does release about a third of the yummy cellulose,
这可以吸收约三分之一的纤维素
but the rest is not digested
剩余的部分体内消化不了
and gets pooped out still tangled up in the lignin.
被排出时还缠在木质素上
Insects like termites can go whole hog on the whole log,
像白蚁这样的昆虫可以吸收所有的营养
because they can chew the wood with their serrated mandibles
因为它们有可以咀嚼木头的锯齿状下颚
and also have the right gut machinery – AKA microbes
并且也具有适合的肠道机制 即微生物
– to break the lignin down on the molecular level.
可以在分子层面上分解木质素
Because lignin evolved in part to help plants defend themselves
木质素的进化从某种程度上是为了
against attackers mainly independently-living microbes
帮助植物抵御自主生活的微生物的攻击
lignin has mostly stymied microbes’ attempts to break it down.
木质素很大程度上阻碍了微生物的分解
But life finds a way …
但生命总会有对策
and a few million years after the evolution of lignin,
在木质素进化了几百万年之后
a few microbes finally untangled the mystery.
一些微生物终于解开了谜团
We still don’t understand all the details,
我们不知道微生物经历了什么
but some microbes seem to produce enzymes
但有些微生物似乎能生产
that use oxygen to break the tight bonds in lignin molecules,
利用氧气来破坏木质素分子中的化学键的酶
setting the cellulose free to be eaten.
使木质素可以被轻易的食用
Which is actually how wood decomposes.
这就是木头被分解的方式
In order for termites and a few other insects to digest wood,
白蚁和其他一些昆虫为了消化木头
they had to turn those independently-living lignin-breaking microbes
把那些自主生活的 分解木质素的微生物
into gut-living lignin-breaking microbes
转变成肠道内生活的微生物
We aren’t sure why more animals haven’t been able to
我们不确定为何没有更多的动物
put these microbes to work for them;
利用微生物帮助消化
perhaps it’s because their guts
可能因为肠道内的化学成分
don’t have the right chemical composition
不适合这些微生物生存
or because other biota already living there
或已经寄生在那里的微生物
are hostile towards newcomers
会排斥新成员
Or maybe termites are just early adopters
抑或白蚁是它们的早期宿主
and millions more years of evolution will
并且数百万年的进化史
lead to more diversity of wood-eating animals. Who knows?
让食草动物更加丰富多样 谁知道呢
Maybe one day woodchucks will chuck wood into their mouths.
没准儿有一天土拨鼠会把手里的木头吃掉
This video was sponsored by the Okinawa Institute of Science and Technology Graduate University,
本视频由冲绳科技研究院赞助
an international graduate school devoted to the advancement of
其为一所致力于在日本和全世界促进
science, education and innovation in Japan and throughout the world.
科学 教育和创新的国际研究生院
OIST offers a fully-funded PhD program and research internship opportunities
OIST提供全额资助博士项目和研究实习机会
that attract talented young scientists from around the world
吸引世界各地有才华的年轻科学家
to work with researchers like Professor Tom Bourguignon,
与汤姆布吉尼翁教授等研究人员合作
whose Evolutionary Genomics lab investigates
他的进化基因组学实验室研究
how insects managed to conquer the world
昆虫如何征服世界
both in terms of animal biomass and biodiversity.
在生物数量和生物多样性两方面
The lab’s research on termite gut microbe DNA
该实验室对白蚁肠道微生物DNA的研究
actually informed this video,
实际上启发了该视频
as they’ve been able to map
他们已经能够描绘出
how the wood-digesting microbes actually evolved
消化木头的微生物是如何进化的
discovering that some microbes only exist within termites.
发现有些微生物只存在于白蚁体内
To learn more about OIST – or maybe even apply
了解更多关于OIST的信息
– visit admissions.oist.jp.
请访问我们的网站
Still here? Sweet.
还在吗 太好了
So, we’re trying something new:
我们正在尝试一些新东西
a cartoon caption contest!
一个卡通标题比赛
Winners (like this one) will be featured at
获胜者(像这个人)将出现在
the end of upcoming MinuteEarth videos.
下一期《分钟地球》视频结尾
Plus they’ll get this super-limited edition
此外 他们将获得这个超级限量版
not-sold-in-stores MinuteEarth tote bag.
非卖品《分钟地球》手提袋
Nice! The next cartoon is already up,
很棒呦 下一版漫画已经出来了
patrons at any tier can play at Patreon.com/MinuteEarth.
任何级别的用户都可以在该网站上观看

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视频概述

在动物界几乎没有动物吃木头,只有少数昆虫(如白蚁)会去吃,这是因为它们体内有与其他动物不同的“咀嚼机制”和“肠道机制”。

听录译者

收集自网络

翻译译者

Fred C

审核员

审核员 V

视频来源

https://www.youtube.com/watch?v=vgRDaemJA1o

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