Carnivorous sharks have a stomach for greens: study

PARIS: It has long been thought that the little shark, a small member of the hammerhead shark family, was a strict carnivore that occasionally drank vegetables by accident.

Not so, scientists said Wednesday. Bonnethead follows an omnivorous diet in which herbaria play an essential nutritional role.

Although researchers have long known that Sphyrna tiburo eats large amounts of seagrass, it has not been thought that it can absorb nutrients.

"Until now, most people thought that herbarium consumption was incidental when these sharks hunted crabs, and so on. who live in seagrass beds, "co-wrote Samantha Leigh, an expert in ecology and evolutionary biology at the University of California. Irvine, told AFP.

Leigh and a team, however, found that seagrasses could account for up to 62% of the animals' diet, in addition to their favorite meal of crustaceans and molluscs.

"Bonnethead sharks consume not only a large amount of seagrass, but they are actually able to digest and assimilate seagrass nutrients, making them clearly omnivorous," the researchers wrote. in the journal Proceedings of the Royal Society B.

"This is the first species of shark to have an omnivorous digestive strategy."

For three weeks, the team conducted a series of laboratory tests during which they fed bathead sharks at 90% seagrass and 10% squid.

They then analyzed the amount of nutrients digested by the animals and their amount excreted.

All carnivores can not effectively digest plant material, but sharks fed a diet rich in herbaria have all gained weight, according to the team.

The animals proved to be as good at digesting fiber and organic matter as young green sea turtles – a species that goes from an omnivorous diet among young people to a vegetarianism committed in adulthood.

& # 39; Really remarkable & # 39;

Leigh described the results as "surprising".

"Bonnetheads has a digestive system that is very similar to other closely related species that are certainly strictly carnivorous, so the fact that they act as omnivores is truly remarkable!"

Developing in saltwater and brackish waters, seagrass beds are the most widespread coastal ecosystem on Earth.

They help filter the water and absorb excess carbon dioxide from the atmosphere.

They also provide homes and nurseries for thousands of fish and invertebrates that make up the lion's share of the diet.

Although sharks do not have secondary jaws that many herbivores use to chew plants, they have very acidic stomachs that can help digestion, according to the researchers.

Ecological implications

With about 4.9 million head sharks in American waters of the Gulf of Mexico and the Atlantic, the results have implications for the management and conservation of seagrass beds.

Understanding sharks of plant material and other digested and excreted marine predators is essential to formulating effective conservation plans, said the study's authors.

Creatures can play a role previously underestimated in the redistribution of nutrients.

"We must reassess [the sharks’] role in critical habitats of marine grasslands as omnivorous as opposed to carnivores, "said Leigh.

With all the evidence showing a strict carnivorous diet for shark ancestors, experts do not know when the first leaders started eating plants.

But the findings suggest that there could be "other" phytophagous sharks out there, Leigh said.