Some sharks can “walk,” and researchers recently discovered how one of these unusual shark species practices taking baby steps. They start when they are just hatched, and the way a hatchling walks is no different from that of older juveniles.
When the tide goes out near a coral reef, a small species of carpet shark it is often left behind. When you get stranded in shallow tide pools with declining and rising oxygen levels temperatures —or worse, stranded on hot slabs of exposed reef—most aquatic species wouldn’t stand a chance. But the epaulet shark (Hemiscyllium ocellatum) can hold its breath for hours and tolerate a range of temperatures. And in a pinch, you can walk.
“During low tide, when the reef is exposed, you can see them walking on the reef,” said Marianne E. Porter, an associate professor at Florida Atlantic University who studies the mechanical structures and movement of sharks. She told WordsSideKick.com that these tough little sharks can walk on land and underwater, gliding over the substrate on four paddle-shaped fins for more than 90 feet (27 meters) until they find a suitable corner where they can wait for the tide
It’s one of nature’s most distinctive survival strategies, but few studies have examined the physics behind the epaulet shark’s locomotion and gait. Now, a new study in the journal Integrative and Comparative Biology is the first to describe the mechanics of how newborn epaulet sharks walk.
Ultimately, the findings may help scientists understand how other aquatic species will tolerate stresses related to climate change, such as rising carbon dioxide levels.
“Epaulet sharks live at the extremes,” said Porter, lead author of the study. “If we want to know what happens to animals in the extreme conditions of climate change, looking at animals already living in these conditions and understanding how they move and cope may be the first step.”
Related: ‘Sharks walking’ caught on video amaze scientists
puffy baby sharks
Both Porter and study co-author Jodie Rummer, a professor of marine biology at James Cook University in Australia, had been studying epaulet sharks for years, but were frustrated to discover that very little information existed about how carpet sharks actually walk. The most recent study to examine epaulet shark locomotion was published in the late 1990s and focused exclusively on mature sharks. The question of how juvenile and baby sharks walk had never been addressed in the scientific literature.
Porter and Rummer suspected that baby sharks would walk differently than older juveniles and adults. Epaulette sharks are born bloated, with their bellies distended by a yolk sac that supplies all their nutritional needs for about a month until they are mature enough to feed on small fish and worms. His baby fat then sheds, giving way to the familiar spindle shape of an adult shark.
“Shape generally affects how we move,” Porter said. “Human babies walk differently to balance their giant heads, and we assumed baby sharks would move their bodies and move their fins differently to accommodate their giant bellies.”
But after examining several videos of young sharks walking and swimming, the researchers were surprised to discover that all the young sharks, from newborn babies to juveniles that did not have a yolk sac, seemed to move in the same way. This observation held true for several key metrics, including speed, tail slapping frequency, body flex, and fin rotation.
“I really thought baby sharks would move differently,” Porter said. “But in science, we made our best guesses based on the available evidence, and our assumptions turned out to be wrong.”
Beyond the walking sharks
It’s not clear why baby sharks don’t adopt gaits more suited to their bulbous bellies. One possible explanation is that gravity plays a role The recent study only looked at sharks that walk underwater, where the volume of the yolk sac does little to hinder movement. In future studies, Porter hopes to see if baby sharks adjust their gait on land to compensate for the extra weight.
Additional research on epaulette shark locomotion may also be useful to evolutionary biologists studying how animals transitioned from water to land, as well as biomechanics researchers who, like Porter, study how fins and feet interact with surfaces and how animals account for gravity and body shape. when moving through different environments.
Meanwhile, epaulette sharks are emerging as models for scientists studying how marine fish adapt to changing oceans. Studying how these unique sharks walk to safety may ultimately lead to a better understanding of how other species move in and out of challenging environmental conditions, including those associated with climate change.
“From an evolutionary perspective, a climate change perspective and even a basic physiological perspective, we can learn a lot from epaulet sharks,” Porter said.
Originally published on Live Science.