未出生的幼鲨会在子宫之间游动，吞食兄弟姐妹
未出生的幼鲨会在子宫之间游动，吞食兄弟姐妹
As macabre as it seems, it's not exactly a secret that in some species of shark the unborn dine on their siblings while still developing in the womb.
尽管看起来令人毛骨悚然，但在某些种类的鲨鱼中，未出生的幼体在子宫内发育的同时，却以兄弟姐妹为食，这并不是什么秘密。
But it turns out we don't know the half of it. A novel kind of ultrasound device has provided biologists with a detailed view of this common act of cannibalism, and in 2018 it revealed they don't just nibble on their neighbour. Embryos will travel between wombs to feast.
但事实证明我们只知其一不知其二。一种新型的超声波装置为生物学家提供了这种常见的食人行为的详细视图，并在2018年揭示出它们不仅仅是在蚕食它们的邻居，胚胎还会在子宫之间游走以饱餐一顿。
No, that's not a typo. Many species of shark mature their eggs or gestate embryos in a left and a right uterus.
是的，我没打错字。许多种类的鲨鱼用左子宫和右子宫来孕育它们的卵或胚胎。
(Tomita etal/Ethology)
For most animals, embryonic movement is rather limited to a bit of squirming and the occasional flip. Even for young that aren't anchored to a placenta, gestation is thought to be a rather sedentary affair.
对大多数动物来说，胚胎期的活动相当有限，只有一点蠕动和偶尔的翻转。即使对于没有固定在胎盘上的婴儿，妊娠也被认为是一种相对静止的事情。
So researchers from Okinawa Churaumi Aquarium in Motobu, Japan, were surprised to find the unborn pups of captive tawny nurse sharks (Nebrius ferrugineus) not only moving around their own uterus, but moving house altogether.
因此，来自日本Motobu市冲绳县美之海水族馆的研究人员惊奇地发现，圈养的黄褐色护士鲨(Nebrius ferrugineus)未出生的幼崽不仅在自己的子宫里动来动去，而且还在搬家。
The discovery came courtesy of a fancy new piece of equipment that allows the kind of ultrasound device you'd use to scan a human pregnancy to be packed up and carried underwater.
这一发现得益于一种新颖的设备，这种设备可以将你用来扫描人类怀孕的超声波设备打包并运到水下。
Over several years, the researchers studied a trio of pregnant tawny nurse sharks on display in an aquarium exhibition tank, capturing more than 40 ultrasound clips.
几年来，研究人员研究了在水族馆展览池中展出的三只怀孕的黄褐色护士鲨，捕捉了40多个超声波片段。
The results provided a family album on a time line, where up to four pups could be seen wiggling about inside each mother.
研究结果提供了一个按时间排列的家庭相册，在相册中可以看到多达四只幼崽在各自母亲的身体里扭动。
In one mother, embryos swapped sides three times. In another, the movement was far more extreme – a total of 24 migrations were recorded across the duration of the pregnancy.
在一个母亲身上，胚胎交换了三次。在另一个母亲身上，这种移动则更极端——在整个怀孕期间共记录到24次迁徙。
(Tomita etal/Ethology)
One of the scans showed the actual room swap taking place, showing an embryo hurriedly pushing its way from one uterus to the other.
其中一项扫描展示了真实的迁徙过程，显示了一个胚胎从一个子宫快速地移向另一个子宫。
We're not talking a leisurely stroll here either. The pup swam at a speedy eight centimetres per second.
它们可不是在闲庭散步，这个胚胎以每秒8厘米的速度游了过去。
One of the female sharks started her pregnancy with two pups in each uterus. After some back and forth, four soon became three. Just under two months later, there were two.
其中一只雌性鲨鱼开始怀孕时，子宫里各有两只幼崽。来回几次之后，四个很快变成了三个。不到两个月，就只有两个了。
By the end of the gestation just a single, no doubt smugly satisfied, winner remained.
到妊娠期结束时，毫无疑问，只有一个得意的赢家留了下来。
