Some sharks can “walk,” and researchers recently discovered how one of these unusual shark species practices taking small steps. They begin when they are newly born, and the gait of juveniles is no different from that of older juveniles.
When the tide near a coral reef goes out, a small carpet species the shark is often left behind. When trapped in shallow tidal pools with decreasing oxygen levels and rising temperatures – or worse, beached 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, it can walk.
“At low tide, when the reef is exposed, you can see them out there 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 Live Science that these hardy little sharks can walk on land and underwater, bumping across the substrate on four paddle-like fins for more than 90 feet (27 meters) until they find a suitable corner where can wait for the wave.
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 newly hatched epaulette sharks walk.
The findings could eventually help scientists understand how other aquatic species will tolerate climate change-related stresses, such as rising carbon dioxide levels.
“Epaulet sharks live in extremes,” said Porter, lead author of the study. “If we want to learn what happens to animals under the extreme conditions of climate change, looking at animals that already live in these conditions – and understanding how they move and cope – could be the first step.”
Connected: ‘Walking sharks’ caught on video amaze scientists
Inflatable baby sharks
Both Porter and study co-author Jodie Rummer, a professor of marine biology at James Cook University in Australia, had been studying basking sharks for years, but they were frustrated to find that very little information existed about how basking sharks actually walk. the carpet. The most recent study to examine the movement of epaulet sharks was published in the late 1990s and focused exclusively on mature sharks. The question of how juvenile and infant sharks walk has never been addressed in the scientific literature.
Porter and Rummer suspected that small sharks would behave differently from juveniles and larger adults. Epaulet sharks are born bloated, with their bellies expanded by a yolk sac that meets all their nutritional needs for about a month until they are mature enough to feed on small fish and worms. Their baby fat then rolls off, giving way to the familiar finger shape of an adult shark.
“Shape generally affects how we move,” Porter said. Human babies walk differently to balance their giant heads, and we hypothesized that baby sharks would rock their bodies and move their fins differently to accommodate their giant bellies.
But after examining numerous videos of young sharks walking and swimming, the researchers were surprised to find that all young sharks, from newborn babies to juveniles without yolk sacs, appeared to move in the same way. This observation was maintained across several key metrics, including speed, tail beat frequency, body flex, and thread rotation.
“I really thought the baby sharks would move differently,” Porter said. “But in science, we take our best guesses based on the available evidence, and our hypothesis turns out to be wrong.”
Beyond the walking sharks
It is unclear why small sharks do not adopt gaits more suited to their bulbous bellies. A possible explanation is that gravity plays a role. The latest study only examined sharks that walked underwater, where most of the yolk sac does not impede movement. In future studies, Porter hopes to see if the baby sharks adjust their walking on land to account for the extra weight.
Further research into epaulet shark locomotion may also be useful for evolutionary biologists who study how the animals transitioned from water to land, as well as biomechanics researchers who, like Porter, study how fins and legs interact with surfaces and how animals consider 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 navigate their way to safety could eventually lead to a better understanding of how other species move into — and away from — challenging environmental conditions, including those associated with climate change.
“From an evolutionary perspective, a climate change perspective, and even a basic physiological perspective, there’s a lot we can learn from epaulette sharks,” Porter said.
Originally published in Live Science.