"First known species of omnivorous sharks"

Scientists claim to have identified the first known species of omnivorous sharks, with 60% of their diet consisting of seagrasses. The discovery, published in the journal Proceedings of the Royal Society B, overturns the idea that all sharks are exclusive meat eaters. Researchers at the University of California at Irvine, USA, discovered that head sharks happily feed on seagrass, eat bony fish, crabs, snails and shrimp.

Omnivores feed on a variety of foods of plant and animal origin. The bonnethead shark is abundant in the shallow waters of the western Atlantic and the Gulf of Mexico, reported The Guardian. Although small compared to sharks, adult females – the largest of the sexes – can still reach an impressive length of five feet. The researchers analyzed the feeding habits of sharks after reading reports on fish consumption in seagrass beds, the flowering marine plant that forms underwater meadows in some coastal waters.

They salvaged the sea grass from Florida Bay and brought it back to the laboratory where they replanted it. As the meadows took root, the researchers added sodium bicarbonate powder made with a specific carbon isotope to the water. This was taken up by the herbaria, giving it a distinct chemical signature. Researchers, including those from Florida International University in the United States, then caught five bald sharks and brought them to the laboratory.

They were fed a three-week diet of grass and squid. Scientists conducted a series of tests on sharks. These showed that they were able to digest seagrass beds with enzymes that were breaking down plant components, such as starch and cellulose.

According to the researchers, the shark, lacking the type of teeth best suited for chewing, can rely on strong stomach acids to weaken plant cells, so that enzymes can have digestive effects.