Scientists have discovered that the world’s largest shark is not actually a carnivore

The largest shark in our oceans is famous for being a gentle giant, and there seems to be more to it than we ever realized. whales and sharks (Rincodon type) are filter feeders, believed to carefully comb the water for small animals such as krill.

Among the young swimmers they catch are greens, which are made up of algae and other organisms that carry out photosynthesis.

This can’t be avoided, but the researchers wondered if these plants were merely garnishes for carnivores, or if they provided a necessary side salad to keep them swimming.

Researchers examining stool and skin samples have determined what ocean bugs 10 meters (32 feet) in length benefit from the giant pools of water they seep through their systems.

“The faeces showed that they were eating krill,” says University of Tasmania biologist Patty Virtu. “But they don’t metabolize much of it.”

Instead, it appears that whale sharks, which are true sharks with cartilage instead of bone, extract nutrients from a heck of a lot of algae.

“It makes us rethink everything we thought we knew about what whale sharks eat,” says Mark Meekan, a fish biologist at the Australian Institute of Marine Sciences. “And in fact, what they do in the open ocean.”

Tissue analysis by Mikan and colleagues also revealed a fatty acid profile that was more consistent with meat than with meat. They found skin rich in arachidonic acid (ARA), found in amounts just large enough to explain the levels found in whale sharks, in floating algae Sargassum.

In 2019, another study using tissue samples found evidence that whale sharks do indeed feed on at least some organisms lower in the food chain, such as plants and algae. What’s more, they aren’t the only carnivorous sharks: Bonnethead sharks (Sphyrna tiburo) Eat a lot of seaweed.

Also called shovelheads for obvious reasons, these animals often ingest plant matter as a result of hunting small prey such as crabs, mollusks, and fish in dense seagrass habitats. So their need to deal with this plant matter passing through their bodies is probably what happened to their ability to digest it.

The researchers suspect that the same may have happened to whale sharks. In their evolutionary past, they may have originally multiplied algae to digest the animals that lived on them (epibionts), but they can now also digest and benefit from the algae themselves.

“So the vision we have of whale sharks coming to Ningaloo to feed on these little krill is only half the story,” Mikan explains. “They actually eat a fair amount of algae, too.”

Unfortunately, to find enough of this floating organic matter, whale sharks must follow oceanic features such as surface currents that hold floating food sources together. These same features also collect pollutants in the ocean like plastic – so whale sharks end up accidentally feeding on those pollutants as well.

Mikan notes that some of this plastic passes through a whale shark’s poop. But it could potentially reduce their gut capacity, slow their digestion, or cause their food to miscarry, the team notes in their paper. This could hurt endangered animals that have suffered a 62 percent decline in population over the past 75 years.

“On Earth, all large animals have always been herbivores,” says Mikan. “At sea, we’ve always thought that animals that got really big, like whales and whale sharks, were feeding one step in the food chain on shrimp-like animals and small fish.

“It turns out that perhaps the system of evolution on land and in water is no different after all.”

This research was published in Ecology.

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