The most fascinating shark discoveries of the last decade

Bamboo sharks walk. Ninja lantern sharks glow in the dark. Whale sharks can carry up to 300 babies at a time, at different fetal stages and from different parents. Zebra sharks experience “virgin birth”.

These are but a mere sampling of the most fascinating shark discoveries of the decade. Some 500 known species of these toothy fish ply the waters of our planet, ranging from bite size to bus size, and scientists are still getting to know most of them. Since 2000, when scientists discovered that shark populations were collapsing worldwide, research on sharks has increased in many fields of study, from paleontology to neuroscience and biomechanics.

A quarter of a century later, one thing is clear: sharks are not the pointless killers that are often portrayed in popular culture. For starters, these fish have large brains that vary in relative size from one species to another.

“Your brain is like a shark’s,” says Kara Yopak, a comparative neuroanatomist at the University of North Carolina at Wilmington. In fact, as one of the most primitive creatures on Earth, sharks were the first to develop what she calls “the vertebrate brain plane,” which contains well-known structures such as olfactory bulbs, the cerebellum, and parts of the forebrain and midbrain.

“The biggest mistake is that sharks are these pre-programmed, small-brain eating machines,” says Yopak. “I have learned that this is not the case.”

As shark science expands, so does the urgency to protect the many species, two-thirds of which are threatened by overfishing, climate change, habitat loss, and poaching. A study suggests that if the world increased its marine protected areas by just 3 percent, it could save 99 of the most threatened sharks, many of which are the top predators that help keep their ecosystems in balance. (Read about six sharks you have never heard of.)

Here are more findings that have changed our knowledge of the sharks in their heads.

Researchers like Barbara Block, a marine biologist at Stanford University, have been putting GPS tags on sharks, tracking their movements, and revealing their secret lives.

Previously, scientists believed that great white sharks near California were trapped near the shore, hunting sea lions and seals. But as tracking technology advanced, allowing scientists to tag sharks for longer periods, Block and his colleagues discovered that predators traveled thousands of miles each winter to a warm area of ​​water in the open Pacific, where they made inexplicable night dives.

Satellites had suggested this Colorado-sized Pacific region, nicknamed the “white shark cafe”, lacked food. But they were wrong. Scientists found an area rich in shrimp, worms, big-eyed tuna, squid, and various deep-sea creatures. Now that we know that this white shark refuge is so crucial to its life cycle, conservationists are working to establish it as a UNESCO World Heritage Site.

On the east coast of the United States in recent years, a great white woman named Mary Lee has become a minor celebrity, jumping onto the beach between Bermuda, Florida, and the Jersey shore and surprising scientists with her frequent excursions. Mary Lee has not appeared since 2017, but she has active accounts on Facebook and Twitter.

Other species of sharks are less peripatetic and perform epic migrations. In 2014, a great white named Lydia became the first known of her species to cross the Atlantic Ocean. And in 2017, a whale shark named Anne broke records by traveling some 12,400 miles across the Pacific Ocean in just over two years.

All sharks are covered in hundreds of thousands of tiny denticles, which mysteriously regenerate when lost.

“Each of them is like one of its own teeth, with a pulp cavity, dentin, and enamel coating,” says George Lauder, a fish biologist and roboticist at Harvard University. “The teeth in our mouths come from ancient scales that covered animals like sharks probably 400 million years ago.”

Recent advances in imaging technology, 3D printing, and robotics have revealed how denticles help sharks swim. In laboratory experiments, Lauder found that shark-skin-like material moved faster and used less energy than smooth material.

The secret? Denticles reduce drag and increase lift and thrust. Size also matters; Smaller denticles speed up, and larger ones slow it down. In individual sharks, the patterns and sizes of denticles can vary.

Scientists once assumed that all fish that fed by filtration used their mouths as strainers: anything too big to go through the clogged holes; the rest came out with the water. But Erin “Misty” Paig-Tran, a functional anatomist at California State University, Fullerton, wondered how that could be true. She studied stingrays and whale sharks that she studied near Cancun, Mexico, fed in the same place at the same time, but ate totally different things.

Testing three-dimensional models of sharks and blanket filters in the laboratory revealed how they do it. By adjusting their swimming speed and the width of their mouths or gill slits, fish can catch their favorite food by manipulating the water that flows through their esophagus. In general, the faster the speed of the water, the smaller the food particles you eat. (Learn how the world’s largest whale sharks are disappearing.)

Species that feed by filtration have different strategies. Whale sharks stop and suck, surface and swallow, or swim with their mouths open. The mega mouths take big shots with their filters covered in denticles. Basking sharks swim with their mouths open.

In 2007, scientists studying the diet of bonnet sharks found bellies filled with up to 60 percent sea grass.

“Everyone thought, myself included, that sharks were carnivores,” says Samantha Leigh, a postdoctoral researcher studying sharks in the Paig-Tran lab. Sure, they may have eaten sea grass by accident, but could their bodies do anything with all those green things?

About a decade later, Leigh, then a graduate student at the University of California, Irvine, fed captive bonnet sharks with seagrasses labeled with isotopic tracers, special molecules that allowed them to see where the nutrients in seagrass moved. by the body. She found that the fish digested about half of the organic matter in the seagrass and incorporated its nutrients into their bodies.

“That is very similar to what some juvenile sea turtles digest,” she says. It is the first omnivorous diet ever seen on a shark. How they do it remains mysterious, but Leigh says that sharks can get help from microbes in their guts, just like humans.

In 2012, Lauder tested the swimsuit material, which was intended to reduce drag like shark skin, worn by 80 percent of winning swimmers at the Sydney Olympics. The Speedo LZR suits, now banned due to concerns about unfair advantage, increased swimmers’ performance by about 7 percent, he says. Swimsuit companies like Speedo are working to design new suits to replace the LZR that are not considered “tech doping.”

Lauder’s research found that the suits weren’t actually reducing drag for human swimmers. “The surface of these suits is nothing like real shark skin,” says Lauder. The real key was that tight full body suits smoothed out any bumps on human skin.

Paig-Tran from California State University says that filter-fed sharks are inspiring designs for high-volume, energy-efficient, self-cleaning industrial filters for purposes such as wastewater treatment, or even removal of microplastics from body parts. Water.

“A lot has happened in the last 10 years,” says Paig-Tran. “The more we learn about sharks, the more fascinating they become.”