The focus of a first-of-its-kind study is a walking shark that breaks all the rules for survival. The epaulette shark's early development was studied by researchers. The benthic shark wriggles its body and pushes with its paddle-shaped fins to walk in and out of water.
Found within the reef flats around Australia's southern Great Barrier Reef, epaulette sharks experience short periods of elevated CO 2 and low oxygen as well as fluctuations in temperatures. The walking shark is able to survive without oxygen for two hours and at a higher temperature than most other animals.
The epaulette shark's ability to move efficiently among micro-habitats under these challenging environmental conditions could affect their survival. Few studies have looked at their body movements. They only focused on adult life stages. This is the first study to specifically examine how they move during early life stages.
FAU researchers collaborated with Australia's James Cook University and Macquaires University to examine differences in walking and swimming between neonate and juvenile walking sharks.
Neonates have a bulging belly due to their retained nutrition through an internal yolk sac. The juvenile are more slender than the older ones because they are more active in looking for food. The yolk that the sharks are storing begins to diminish as they get older. The shark starts to eat when the yolk is low.
Researchers expected to see differences in performance in these sharks because of their different body shapes. They used 13 landmarks along the fins, girdles and body midline to test their hypothesis. They quantified the various parts of the body, such as the tail beat, fin rotation, and duty factor.
The results of the study show that the differences in body shape did not affect the movement of sharks. Between early life stages, fin rotation and tail beat frequencies were consistent.
Neonate and juvenile epaulette sharks have different feeding strategies, but the loco motor kinematics are the same. The findings show that the effects of the yolk sac on body shape are not different to those of the juvenile.
The ability to move within and away from challenging conditions in their habitats is studied by the epaulette sharks. The key to survival for a small benthic mesopredator is its ability to maneuver into small reef crevices. Climate change may be related to their sustained performance under challenging environmental conditions.
An important next step in understanding how this group of important mesopredators will respond to future ocean conditions is studying the link between locomotion and the mechanisms needed to tolerate challenging environmental conditions.
Porter said that studying how locomotor performance changes over the course of early ontogeny can offer insights into the mechanisms that allow animals to compensate for constraints to meet ecological demands.
More information: Marianne E Porter et al, Aquatic Walking and Swimming Kinematics of Neonate and Juvenile Epaulette Sharks, Integrative and Comparative Biology (2022). DOI: 10.1093/icb/icac127
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