VIDEO: Bamboo sharks play dead
WHILE WORKING ON his thesis for the University of Western Australia, Ryan Kempster made a fascinating revelation about bamboo sharks. When faced with predators, the embryos of this species – developing within their egg cases – will shut down, he says, effectively “playing dead”.
The embryo will actually stop respiring, remain completely still and greatly reduce its heart rate, making it difficult for predators to detect it. The bigger the threat a predator poses, the longer the amount of time that the embryo will play dead, he says (see video above, courtesy of UWA).
Baby bamboo sharks are able to use vibrations to track movements, but they also have an electro-sensory sense that uses biological electric fields to detect movement. These tiny embryos use their electro-sensory pores to detect predators, such as other sharks.
Electric sense of sharks
Commonly found in the Indo-West Pacific region, near the southern coast of New Guinea and the northern coast of Australia, these full-grown, nocturnal bottom-dwellers have other unusual defences too. As adults, they have the ability to survive in low oxygen conditions by switching off non-essential brain functions, and can also survive up to 12 hours out of the water.
Though adult bamboo sharks usually eat small fish, and seafloor invertebrates, such as crabs, Kempster says that they would probably eat their own newborns, if it weren’t for a secreted hormone that reduces their appetite.
Ryan Kempster’s short film documenting the phenomenon, Survival of the Stillest (above), will be shown this week at the prestigious US film festival, Beneath the Waves, in Norfolk, Virginia.
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