The shark that walks learns to walk as a child: it survives without oxygen for two hours

The shark that walks learns to walk as a child: it survives without oxygen for two hours

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A walking shark newly discovered that breaks all the rules for survival is the focus of a study by Florida Atlantic University and collaborators in Australia.

They investigated how walking and swimming changes in the early development of the epaulet shark (Hemiscyllium ocellatum). This small benthic shark (about one meter), which lives in the reefs, walks both in and out of the water moving his body and pushing with their paddle-shaped fins.

Found within reefs around South Australia’s Great Barrier Reef, epaulet sharks experience short periods of CO2 elevated and hypoxic (low oxygen), as well as fluctuating temperatures as reefs become isolated with the outgoing tide.

Amazingly, this walking shark is capable of survive to anoxia complete (without oxygen) during two hours without adverse effects and at a much higher temperature than most other hypoxia-tolerant animals.

The epaulet shark’s ability to move efficiently between microhabitats in these challenging environmental conditions could to affect directly their survival and their physiological responses to climate change.

However, very few studies have examined their body movements as they focus mostly on stages of adult life. No study has specifically examined their locomotion during early life, until now.

FAU researchers, in collaboration with James Cook University and Macquarie University in Australia, examined the differences when walking and swimming in sharks newborn and juvenile walkers.

Research indicates that newly born retain embryonic nutrition through an internalized yolk sac, resulting in a bulging belly. In contrast, juveniles are slimmer because they actively seek out worms, crustaceans, and small fish. During development, the yolk that newborn sharks store begins to diminish as they become juveniles. As the yolk is depleted, the shark begins to actively forage.

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Due to differences in body shapes, the researchers expected to see differences in the locomotor performance of these walking sharks. To test their hypothesis, they examined the locomotor kinematics of hatchlings and juveniles during the three aquatic gait modes they use (slow-to-medium walking, fast walking, and swimming) using 13 anatomical landmarks along the flippers, girdles, and tail. midline of the body.

They quantified the kinematics of the axial body (velocity, amplitude and frequency of the tail beat and body curvature) and the flexion of the axial body, the flipper rotation and the duty factor and queue kinematics.

Surprisingly, results published in the journal Integrative & Comparative Biology showed that differences in body shape did not alter the kinematics between newborn and juvenile walking sharks. Overall speed, fin rotation, axial flexion, and tail-beat frequency and amplitude were consistent between early life stages.

The data suggest that locomotor kinematics are maintained among neonate and juvenile epaulet sharks, even when their feeding strategy changes. These findings suggest that the submerged locomotion in newborns is not affected by the yolk sac and the effects it has on body shape, as all aspects of submerged locomotion were comparable to those of juveniles.

Studying the locomotion of the epaulet shark allows us to understand the ability of this species

“Studying epaulet shark locomotion allows us to understand the ability of this species, and perhaps related species, to move in and out of the challenging conditions of their habitats“, Marianne E. Porter, lead author and associate professor in the Department of Biological Sciences at FAU, said in a statement.

“In general, these locomotor traits are key code for the survival of a small benthic mesopredator that maneuvers in small reef crevices to avoid aerial and aquatic predators. These traits may also be related to their sustained physiological performance under challenging environmental conditions, including those associated with the climate changean important topic for future studies,” he says.

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