Some sharks are "walking" to find more favorable conditions

A new study led by the Florida Atlantic University (FAU) has found that epaulette sharks – a small but feisty aquatic creature commonly found on shallow reefs in Australia and New Guinea – have evolved an extraordinary ability to walk on land in order to have better chances of survival as sea temperatures rise and climate changes.

While many other shark species have ambulatory capacities, allowing them to walk in shallow water, this is the first species able to tolerate hypoxia (lack of oxygen) for an extended period of time, which helps them travel up to 30 meters on dry land using paddle shaped fins. According to the experts, these remarkable capacities enable the reef-dwelling sharks to survive increasingly hostile environments.

“Such locomotor traits may not only be key to survival but also may be related to their sustained physiological performance under challenging environmental conditions, including those associated with climate change,” the study authors explained. “Findings to date suggest that this species has adaptations to tolerate some, but perhaps not all, of the challenging conditions predicted for the 21^st century.”

The scientists discovered that the epaulette sharks are able to walk both slow and fast, as well as swim, offering them the possibility to successfully cross patches of land to reach more favorable environments.

“You might not think of beautiful, tropical beaches as harsh but in reality tidepools and coral reef environments are pretty harsh, subjected to warm temperatures when the tide is out and a lot of changes, a lot of things happening when the tide comes in and goes out,” said study lead author Marianne Porter, a professor of Biomechanics at FAU. “These little sharks can move from tidepool to tidepool, allowing them to access new pools to forage for food, or tidepools with better oxygenated water.”

“Our collaborators in Australia have found they are able to withstand climate change conditions very well. These sharks are great models in starting to look at how these changing conditions may affect vertebrates in general, and other species, and can help us reflect what we might see in future oceans.”

Besides helping them escape a variety of environmental stressors, the ability to walk on land from one place to another also provides them unique opportunities to escape predators, and reach areas with more plentiful food sources and less competition for them.

The study is published in the journal Integrative & Comparative Biology.

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By Andrei Ionescu, Earth.com Staff Writer