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The candiru is a legendary monster.
牙签鱼是一种传说中的怪物。
This parasitic Amazonian catfish is said to swim up into the urethras of unsuspecting bathers and devour their genitals from the inside out.
据说这种亚马逊河流中的寄生鲶鱼能够游进毫无戒备心的沐浴者的尿道中并从里边吞食他们的生殖器。
It's a terrifying tale—and one that we've actually told here on SciShow a couple of times.
这种恐怖的传说，我们在《科学秀》也讲过多次。
But science has shown that this story is just that—a story—and one that is too awful to be true.
但科学已经证明这个故事只不过是个故事而已，根本就不是真的。
As far as scholars can tell, the tales began in the early 1800s.
据学者们所知，这个故事源于19世纪初期。
European explorers and naturalists trekking through the Amazon basin heard about the candiru from indigenous communities.
徒步亚马逊盆地的欧洲探险家和自然学家从土著那里听说了牙签鱼。
As they explained in their reports, they were told the parasitic fish is attracted to human urine, so you should never pee in the Amazon river.
正如他们在报告中所述，土著人告诉他们，这种寄生鱼会被人类的尿吸引，所以你绝不应该在亚马逊河中尿尿。
You shouldn't even pee into the water from dry land—the fish can supposedly swim up a stream of urine to find its way into a person's urethra.
你甚至都不能站在干地上往水里尿尿—这种鱼可以顺着尿流游进人们的尿道中。
And once that happens ... well, there were some removal methods suggested.
一旦发生...解决方法有几种。
Some herbs can supposedly be used to dissolve the offending parasite.
据称一些药草可以让这种寄生鱼消失。
But the most effective method of removal is, of course, prompt amputation.
但是最有效的方法，当然是立即切断。
And all of that makes for a great monster myth but it doesn't jive with science.
所有这一切造就了这么一种怪物，但是这是没有科学依据的。
The candiru of legend is most likely the South American catfish Vandellia cirrhosa.
牙签鱼的传说最有可能是南美鲶鱼寄生鲶鱼。
It's a parasitic catfish that inserts its head into the gills of larger fish to drink their blood,
这是一种寄生鲶鱼，它们能够将它们的头插入其他大鱼的鱼鳃中并吸食它们的血，
so it might not be that far out to think it could insert itself into people, too.
所以就不难觉得它们也会将自己插入人类体内。
But it's about five centimeters long and about a centimeter wide.
但是它有约5厘米长，约1厘米宽。
That's small enough to fit in the gill openings of the fish it targets, but not small enough to slip into a human urethra.
这么小的体型足够塞入目标鱼的鱼鳃中，但还没有小到可以溜进人类的尿道中。
A urethra could be pried open, in theory, but these fish don't have any appendages to do that with.
尿道可以被撬开，但这些鱼没有这么做的工具。
Also, if a candiru did somehow enter a human urethra, it would quickly suffocate so it wouldn't be chilling up there drinking blood.
同样，如果一只牙签鱼不知怎么的就进入了人类尿道中，它也会迅速窒息，因此无法在那里吸血。
But the biggest problem with this whole story is that the candiru isn't attracted to human urine.
但是这整个故事中最大的问题就是牙签鱼根本不喜欢人类尿道。
Scientists used to think these parasites sought out the nitrogen-containing wastes, basically, pee that fish excrete from their gills.
科学家们过去认为这些寄生物想获得含氮的水，也就是从鱼鳃中排出来的尿。
That's because these catfish often hunt in turbulent, muddy waters at night,
这是因为这些鲶鱼经常在夜晚湍流的浑水中捕食，
so it would make sense that they'd rely more on chemical attractants rather than visual cues to find their meals.
所以它们更加依赖于化学引诱物而非视觉线索寻找食物也就说得通了。
And if they were sniffing for nitrogen-containing compounds like ammonia and urea to find their prey,
如果它们闻到了含氮混合物的味道，比如氨和尿素，为了寻找食物，
it follows they'd also zero in on human urine since it contains some of the same stuff.
它们就会跟着味道，也会对准人类尿液，因为其中包含同种物种。
But in 2001, marine scientist Stephen Spotte tested this assumption in the lab.
但在2001年，海洋科学家Stephen Spotte在实验室中对这种假设进行试验。
He and his team exposed candiru to a range of attractants
他和他的团队将牙签鱼暴露在各种引诱物质中
fish slime, ammonia, amino acids, and, yes, even human urine and the candiru didn't go for any of them.
如鱼黏液、氨、氨基酸，还有没错，人类尿液，并且牙签鱼并没有选择其中任何一种。
The catfish did respond to the sight of goldfish, though
虽然牙签鱼确实对视线中的金鱼有反应
which suggests that, despite the murky depths it hunts in, it actually relies on eyesight to find its meals.
这表明，虽然它可以深入黑暗的深处，但其实它还是依靠视觉寻找食物。
Which brings us back to all those stories about pee-seeking fish.
现在让我们再回到找尿鱼的故事中。
As a 2013 review paper notes, medically confirmed attacks by the fish on humans are very hard to find.
正如一篇2013年的综述论文所述，在医学上，鱼类袭击人类的确认案例非常难以发现。
Most of the stories were perpetuated by a few 19th century European explorers who might have misinterpreted oral accounts accidentally, or willingly,
大部分故事都来自一些19世纪的欧洲探险家，他们可能意外地或乐于误解那些人的口述
for the sake of a sensational tale. None of them seems to have witnessed actual cases.
只为塑造一个耸人听闻的故事。他们中没有一个人亲眼目睹过事实。
In fact, there's only one candiru-penis incident that's been medically documented.
事实上，医学上只记载了一起牙签鱼进入阴茎的事故。
In 1997, a man in the Brazilian city of Manaus was allegedly brought into the hospital with a candiru wedged painfully in his urethra.
1997年，一名位于巴西玛瑙斯市的男性来到了医院，据称一只牙签鱼进入了他的尿道。
A urologist was able to remove the fish after hours of surgery, and he wrote the whole thing up and published the case.
一名泌尿科医师经过几个小时的手术后将其取出并将这件事写了下来并出版成案例。
But, other scientists question the veracity of this account.
但其他科学家质疑这一描述的真实性。
For one, the patient insisted that the fish swam up his stream of urine.
其一，这名病人坚称这条鱼顺他的尿流游了进去。
This is an impossible feat: the small fish would have had to swim faster than the stream of pee to climb it,
这是不可能的事情：这种小鱼要比尿流速度游得更快才能爬进尿流，
which is challenging, since the average human urinates at a brisk 8 to 15 milliliters per second.
这是一个挑战，因为人类平均尿流速度为8到15毫升每秒。
The fish would have also had to fight the pull of gravity while swimming upward,
这种鱼在向上游的时候，还需要和重力对抗，
and to make matters more complicated, it would have had to stay completely submerged in the urine
更复杂的是，在尿液中，它需要完全呆在水面下
since the air around the urine is not dense enough for the fish's fins to push against.
因为尿液中的空气不够密集，鱼鳃无法进行推挤。
And that's not likely since a person's urine stream is generally pretty thin compared to a centimeter-wide fish.
并且这是不可能的，因为人类的尿流和1厘米宽的鱼相比更薄。
Now, some fish can jump pretty high—salmon, for instance, can leap up to 2 meters—
一些鱼可以跳的相当高—比如鲑鱼可以条约2米高—
but it's not clear these catfish are able to jump out of the water at all, let alone well.
但是还不清楚这些鲶鱼是否可以跳出水面。
And even if one did leap at a person's genitalia, as we said before, it has no way to widen the urethral opening to get inside.
而且即便有那么一条确实向人类生殖器扑了过去，它也没有办法打开尿道进到里边。
And there's no reason the fish would even do that in the first place since it isn't attracted to urine.
并且它们甚至没有理由这么做，因为它们不会被尿吸引。
There are also inconsistencies with the urologist's findings. He apparently kept the surgically removed parasite.
还有一些和泌尿科医生的发现相矛盾的地方。显然他留下了那个通过手术移除掉的寄生物。
And, according to Stephen Spotte who visited the urologist and saw the infamous intruder first hand
Stephen Spotte拜访了那名泌尿科医师并亲眼看到了那个臭名昭著的入侵者
the fish was far too large to fit in a urethra, and didn't show any signs of having been inside a human being.
这条鱼太大了，更本无法进入尿道，也没有任何迹象表明这条鱼曾在人体内呆过。
For example, it still had its spines, which the doctor had claimed were removed during the surgery.
例如，它的脊椎还在，那名医生声称在手术过程中，脊椎已经移除了。
With all these inconsistencies, it's almost certain that this case is a hoax and, again, it's the only documented case.
所有的这些矛盾几乎可以确定这个病例是一场闹剧，而且仅有这一起记录病例。
In the end, there are several scientific reasons why these fish wouldn't do this awful behavior.
最后，有几个科学原因可以解释为什么这些鱼不会做出这种可怕的事情。
So if you decide to go swimming in the Amazon, your urethra should be safe from parasitic catfish.
所以如果你决定要去亚马逊游泳，你的尿道应该不会被寄生鲶鱼入侵。
You might want to watch out for the piranhas, though. Or the electric eels. Or the bull sharks, or caimans…
虽然你可能需要当心水虎鱼，或者电鳗，或者公牛鲨，又或者凯门鳄....
I'm just saying, the Amazon is still a dangerous place! Thanks for watching this episode of SciShow!
我是想说，亚马逊仍然是一个非常危险的地方！感谢收看本期《科学秀》！
If you liked learning the science behind this below-the-belt myth, you might like the truth-seeking done on our podcast SciShow Tangents.
如果你想了解这个虚构故事背后的科学，你或许会喜欢寻求真理性的节目SciShow Tangents。
Every week, four people who work on SciShow get together to talk about science related to a central topic.
每周科学秀中的四人汇聚在一起讨论一个与中心话题相关的科学。
There are different segments, like one where someone presents one true fact and two fake ones and everyone else has to try and figure out which is true.
其中包含不同的片段，比如一个人说一件真事和两件假事，其他人来猜真假。
With stories like the candiru out there, it can be kind of hard to tell what's real and what's made up!
就像是牙签鱼这样的故事，真假难辨哟。
Also, they tend to go on lots of sciency tangents, hence the name "SciShow Tangents".
同样，他们还会偏个题讲些其他事情，所以这个节目的名字叫SciShow Tangents。
You can check it out wherever you get your podcasts!
大家可以去podcast里看看！
