Scientists identify first known 'vegetarian' shark

The bonnethead shark loves snacking on tasty meadows of seagrass

To find out if the shark was eating seagrass out of desire or because it happened to be stuck on the meat it ate.

While more research needs to be done, the scientists say that there may be more omnivorous shark species lurking in the ocean.

"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 their paper recently published in the journal Proceedings of the Royal Society B.

The bonnethead shark, a diminutive species that reaches up to 3 feet in length, lives in the shallow sea grass meadows off both coasts of the Americas. They are abundant, with a population of about 4.9 million, Newsweek reported. Surprisingly, the experiment saw the initially thought carnivorous sharks gained weight from the seagrass-heavy diet.

Omnivores, on the other hand, are capable of eating meat, but they can also digest plant material.

"Until now, most people thought that seagrass consumption was incidental when these sharks were hunting for crabs, etc. that live in the seagrass beds", Leigh said in a statement. While some animals chomp up animal and plant indiscriminately, bonnethead sharks draw valuable nutrients from the seagrass, digesting it properly.

Smaller cousins of the hammerhead shark, bonnetheads had been spotted munching on seagrass in the past, in addition to crustaceans and other shellfish, but marine biologists had always assumed the veggie mouthfuls were purely accidental, reports the New Scientist.

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. But, as has been shown by autopsy, sometimes in the stomachs of these sharks have found up to 60% of plant foods.

The researchers able to confirm that the bonnethead sharks possessed the enzymes needed to break down fibres and carbohydrates.

In spite of the fact that co-authors of the study Samantha Leigh, Yannis Papastamatiou, and Donovan German presented their research on the shark's peculiar omnivorous habits at the Society for Integrative and Comparative Biology's yearly gathering in January, the newly found information says that this is the "first species of shark ever to be shown to have an omnivorous digestive strategy", as per the authors.

These are critical ecosystems that provide habitat for thousands of fish species, filter the surrounding water, absorb carbon dioxide from the atmosphere and produce large quantities of oxygen. However, many seagrass meadows are declining in health and abundance.

"Predators control the populations of the herbivores upon which they prey, which, in turn, control the vegetation upon which they feed".

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