两头动物是如何炼成的
你可能会说吉列尔莫·庞斯（Guillermo Ponz）是科学界的怪物猎人，即使他本人认为“怪物”这个词并没有真正抓住他的研究主题。庞斯说：“它们都是普通动物，只不过经历了不同寻常的发育阶段，最终长出了你预期之外的身体结构。”
令这位西班牙马德里的研究人员着迷不已的，是一群诡异而奇妙的动物，毕竟他的研究对象是两头虫。“有些蠕虫通常状态下就是普通蠕虫，一头一尾，非常正常，但有时候它们可能有两个脑袋或者两条尾巴。另一方面，还有一些蠕虫长着一个脑袋加上许多条尾巴。”庞斯补充说。
从专业角度来说，他研究的是分支环节动物，意思就是像蚯蚓这样的蠕虫经历幼虫阶段之后长出两个脑袋，或者自发长出两条尾巴，又或者其他一些附肢混合组合到一起。
我们知道某些物种，例如一些蝾螈和昆虫，可以在有需要时重新长出附肢，但还有一类环节动物门的蠕虫，它们重新长出的是我们在动物王国中见所未见的。它们的身体分成多个节段，例如蚯蚓的身体呈环节状，这能帮它们在遇到麻烦的第一时刻重新长出脑袋或者尾巴。还有更疯狂的情况，如果把它们对半切开，它们还能重新长出全新的右半身。
庞斯表示：“能做出这些疯狂行为的蠕虫非常奇怪，这是蠕虫‘不应该’做到的事情。”庞斯开始研究解剖结构上决定这些蠕虫生长存活的死亡限定长度，自此他便完全沉迷其中。
他意识到自己的团队并不是第一个着迷于此的团队，18~19世纪是这些“怪物”的黄金研究年代……[查看全文]
Two-Headed Worms Tell Us Something Fascinating about Evolution
You might say that Guillermo Ponz
 is a scientific monster hunter–even though he thinks that term, “monster” never really captured his subjects right. 

Guillermo Ponz: So they're regular animals that have gone through different developmental processes that would end up building a body, that is not what you expect.
Papp: What this researcher based in Madrid, Spain, actually loves, is the oddly amazing animals. After all, he studies two-headed worms.
Ponz: We have these worms that are usually regular worms like with one head and one tail, that's normal, but sometimes they may have two heads or two tails. And on the other side, there are worms, which have one head and many tails always. 
Papp: Officially, he looks at bifurcated annelids, meaning things like earthworms that have come out of their larval stage with two heads, or spontaneously sprouted two tails, or ... some other combination of mixed up appendages.  
We know that certain species, like some salamanders and insects, have the ability to regrow appendages in a time of need. But there's this one phylum of worms, the annelids, that can re-grow unlike anything else that we've ever seen in the kingdom. 
Their segmented bodies, like an earthworm with rows of ringed compartments, help them easily regrow a new head or tail at the first sign of trouble. 
Or even crazier, they can regrow an entirely new right side of their body if sliced in half. 
Ponz: … worms that do these crazy things that are very weird, very, you know, very, very strange things that these worms should not, quote-unquote, should not do. 
Papp: Once Ponz started studying the anatomically death-defying lengths to which these worms would go to grow and survive, he was totally pulled in. 
And he realized that he and his team weren’t the first to be fascinated. Ponz found that there was a golden age of research on “monster creatures” during the 18th and 19th centuries...[full transcript]
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论文信息
Ponz‐Segrelles, G., Ribeiro, R. and Aguado, M., 2021.
Monsters
 reveal patterns: bifurcated annelids and their implications for the study of development and evolution.
Biological Reviews
, 97(3), pp.896-922.

doi: 10.1111/brv.12826
封面图来源：Unsplash
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