有的鲨鱼也是吃素的

目前，科学家们确定了第一个不只吃肉的鲨鱼物种。

The bonnethead shark, a smaller relative of the hammerhead, has been found to digest vast amounts of seagrass as well as meat.

窄头双髻鲨(bonnethead shark)是槌头双髻鲨(hammerhead shark)的小型亲戚，如今已被确认能够像消化肉类般消化大量海草。

The shark was long thought to be a strict carnivore that occasionally ingested greens by accident, passing them through the gut without processing them properly.

长期以来，鲨鱼一直被严格归类为肉食性动物。即使它们偶尔误食一些植物，这些植物在通过肠道时也不会被消化。

But in tests they proved better at digesting vegetable matter than a panda and almost as good as sea turtles, suggesting plants are a key part of their diet.

但现在有试验证明，它们消化植物的能力比熊猫还强，几乎与海龟一样厉害，这表明植物也是它们的关键饮食组成。

Sharks had previously been 'uniformly accepted as carnivores', according to the researchers from the University of California, Irvine.

加州大学欧文分校的研究人员表示，鲨鱼以前「被一致视为肉食性动物」。

They found, however, that seagrass can form up to 62 per cent of the bonnethead diet, alongside their preferred meal of crustaceans and molluscs.

然而，他们现在发现，在窄头双髻鲨的饮食习惯中，海草占到了高达62%的比例。其次才是它们爱吃的甲壳类动物和软体动物。

Although researchers have long known that the tiny species eats copious quantities of seagrass, it was not believed to absorb any nutrients from it.

虽然研究人员早就知道这种小型物种会吃掉大量的海草，但却认为它们不会从中吸收任何营养成分。

'Until now, most people thought that seagrass consumption was incidental when these sharks were hunting for crabs that live in the seagrass beds,' said study co-author Samantha Leigh.

该研究共同作者Samantha Leigh表示：「至今为止，大多数人都认为它们只是在海草床上寻找螃蟹时偶然误食海草」。

Over the course of three weeks, the team conducted a series of lab-based trials in which they fed bonnethead sharks a diet of 90 per cent seagrass and 10 per cent squid.

在三个星期内，该团队进行了一系列基于实验室的试验。在这些试验中，他们给窄头双髻鲨喂食了90%的海草与10%的鱿鱼。

They then analysed how much of the nutrients the animals digested, and how much they excreted.

随后，他们再分析这些动物消化了多少营养素，以及排出了多少。

Not all carnivores can digest plant material efficiently, but sharks fed the seagrass-heavy diet all gained weight, the team found.

研究团队发现，并非所有肉食性动物都能有效地消化植物，但大量喂食海草后的鲨鱼都增重了。

The animals were found to be as good at digesting fibre and organic matter as young green sea turtles - a species that transforms from eating an omnivorous diet in youth to committed vegetarianism in adulthood.

他们还发现，这种动物对于纤维与有机物的消化能力堪比年轻的绿海龟(绿海龟年轻时为杂食性动物，成年后则变为素食动物)。

'Bonnethead sharks are not only consuming copious amount of seagrass but they are actually capable of digesting and assimilating seagrass nutrients, making them clear omnivores,' the researchers wrote in the journal Proceedings of the Royal Society B.

研究人员在《Proceedings of the Royal Society B》期刊上写道：「窄头双髻鲨不仅会食用大量海草，而且它们实际上还能够消化与吸收海草中的营养素，这就令其明显成为了杂食性动物」。

Averaging 30-48 inches (76-120cm) in length and weighing up to 11 kilograms (24lb), bonnetheads are found on the Atlantic and Gulf of Mexico coasts of the US.

据悉，窄头双髻鲨平均长度为76-120厘米，重达11千克左右，且在大西洋与美国的墨西哥湾海岸均有出没。