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Meet the bonnethead, the world’s first omnivorous shark – CNET

New sharks at Chessington World of Adventures

One of a pair of new Bonnethead sharks at Chessington World of Adventures, Surrey.

Steve Parsons/PA Images via Getty Images

Sharks, we thought we knew you. But it turns out we may have had it all wrong.

Thanks to researchers at the University of California, Irvine, new information has come to light about the bonnethead shark. The sharks were thought to be solely carnivorous, but now there’s evidence they’re omnivorous — they can eat both animals and plants.

And that plant is seagrass. While some animals chomp up animal and plant indiscriminately, bonnethead sharks draw valuable nutrients from the seagrass, digesting it properly. The non-plant side of their diet includes crustaceans, squid and mollusks.

This kind of information is beneficial to scientists understanding the ecosystem. Sharks were thought to have stomachs that could only digest high-protein foods and nothing else. Being able to digest plants as well means the bonnethead shark’s stomach has different digestive biochemistry.

“Initially, the thought was that the bonnethead shark was accidentally consuming seagrass while hunting for crabs, squid, and other small invertebrates that make seagrass meadows their home,” research leader and marine biologist Samantha Leigh told Gizmodo.

By working with five sharks in captivity over three weeks, the researchers ran a test involving feeding the sharks a diet of 90 percent seagrass and 10 percent squid. The researchers collected and analysed the faecal matter of the sharks, discovering that around half the organic matter in the seagrass was digested.

Now scientists will have to reevaluate the role bonnethead sharks play in seagrass environments and what the implications are.

The research was published Wednesday in Proceedings of the Royal Society B. The findings were also presented at the Society for Integrative and Comparative Biology’s annual meeting in January.

Research leader Samantha Leigh has been contacted for further comment. 

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