Even the tiniest of the sharks have the incredible ability to defend themselves. A new study on unborn sharks within their leathery egg cases, finds that these babies can sense the electric field of a predator and freeze to avoid detection.
A number of sharks deposit their embryos in square shaped eggs sometimes called the devil’s purse or the mermaid’s purses. These eggs usually have long tendrils on both ends to hold them at each corner.
Sharks also have highly sensitive receptors known as the ampullae of Lorenzini to detect the electric fields generated by the muscle contractions of potential prey. Now researchers find that their unborn babies also have strong senses that help them detect electric fields of potential predators.
The researchers studied the brown banded bamboo shark and found that the babies of these sharks spent up to five months inside their egg cases. During this time they were vulnerable to attack from fishes, mollusks and other large marine animals.
When the scientists induced electric field similar to that of predator fishes in the ocean in their labs, the unborn baby sharks in the eggs reacted by ceasing all movements of their gills and keeping their bodies perfectly still.
Researcher Ryan Kempster, a marine neuroecologist at the University of Western Australia believes that this finding could help in the future to make shark repellants more effective.
“There are a variety of commercially available, nonlethal electric shark repellents, but the scientific data supporting their effectiveness is limited,” Kempster told LiveScience.
The research has helped analyzed how different types of sharks react to different types of predator electric fields and how their reactions can or cannot change over time.
He also believes that sharks are feared all over the world, but it is these marine creatures that are under more threat by humans than vice versa.
“As founder of the shark conservation group Support Our Sharks, a driving force behind my work is not only in producing a repellent to protect ocean users from potential attack, but also to protect sharks from being killed,” Kempster said.
“In an attempt to make the ocean a safer place, governments in western Australia, Hawaii and France’s Reunion Island have previously implemented pre-emptive killing of sharks. Given the crucial role that sharks play in ocean ecosystems, I believe it is much more appropriate to take advantage of nonlethal shark-control measures instead.”
As sharks are getting caught accidentally in fish nets, a superior repellant that can trigger electric fields that relate to predators can help sharks stay away from these nets.
“By keeping sharks away from fishing gear, to decrease the number of sharks unnecessarily killed each year,” Kempster said.