The hammerhead relatives consume copious amounts of sea grass, and have the digestive machinery to process it—making them true omnivores. Christopher Intagliata reports.

锤头鲨的亲戚消耗大量的海草，并且有消化机制来消化——这使它们成为真正的杂食动物。克里斯托弗·因塔利亚塔报道。

撰文播音：克里斯托弗·因塔利亚塔（Christopher Intagliata）

翻译：邱燕宁

审校：郭晓

Sharks aren't typically thought of as vegetarians. Or even omnivores. But about 10 years ago, scientists documented a dainty relative of the hammerhead shark, known as a bonnethead shark, consuming copious amounts of sea grass.

鲨鱼通常不被认为是素食主义者或者杂食动物。但大约10年前，科学家记录了锤头鲨的一种小巧的近亲，名叫窄头双髻鲨，它们消耗了大量的海草。

"A lot of people kind of just thought they were consuming it incidentally, after going after crabs and squid and other little invertebrates that live in the sea grass meadows." Samantha Leigh, a PhD candidate at the University of California, Irvine. "So everyone thought they were kind of just passing it through their system and not really getting anything from it." 

“很多人都只是认为，它们在追赶螃蟹、乌贼和其他生活在海草场中的小型无脊椎动物时，顺便吃了海草。”加州大学尔湾分校博士生Samantha Leigh如是说。“所以每个人都认为海草只是通过了它们的消化系统，鲨鱼并没有从中得到任何东西。”

So Leigh and her colleagues hauled five of the small sharks back to a Florida lab, and put them on a three-week diet: 90 percent sea grass, 10 percent squid. And analyzed the digestibility of that diet. Turns out, the sharks actually put on pounds, and were able to digest the sea grass just as well as young green sea turtles do. 

于是，Leigh和她的同事们把5条小鲨鱼带回了佛罗里达的实验室，让它们进行三周的特殊饮食计划：90%的海草，10%的乌贼。之后他们分析了鲨鱼对这些食物的消化率。事实证明，鲨鱼的体重的确增加了，它们能像年轻的绿海龟一样消化海草。

"It seems like even though the bonnethead shark has what scientists would deem a carnivorous gut, they are definitely acting like omnivores. So there's probably something going on, on probably a microbial level, that's helping them break down this sea grass."

The full nutrition info is in the Proceedings of the Royal Society B. [Samantha C. Leigh et al., Seagrass digestion by a notorious ‘carnivore’]

“看起来，尽管窄头双髻鲨拥有科学家认为的食肉肠道，但它们的行为确实像杂食动物。”所以可能有某种东西，比如在微生物水平上，帮助它们分解海草。

完整的营养信息刊登在《英国皇家学会学报B》（Proceedings of the Royal Society B）上。

The study also gives coastal ecosystem managers something new to chew on: these sharks are like lawn mowers, trimming the sea grass, digesting it, and, yes, recycling it. "So they likely play more of a stabilizing role in food web dynamics. They're not a top apex predator. And they're probably playing a large role in nutrient transport in those sea grass meadow ecosystems as well." 

这项研究也给了海岸生态系统管理者一些新的东西去研究:这些鲨鱼就像割草机，修剪海草，消化并循环利用它们。“因此，它们在食物网动态中扮演的角色更更像是个稳定者。它们不是顶级掠食者。它们可能在这些海草草甸生态系统的营养运输中也扮演着重要的角色。”

As for whether we might convince more sharks to have a side salad with dinner? "I don't know that we'll be able to do that anytime soon."

至于我们是否可以让更多的鲨鱼在晚餐时吃些沙拉。“我不知道我们是否很快就能做到。”