Video: Shark Embryo Responds to Electrical Stimulus by Ceasing Gill Movements

Posted on January 9, 2013

This video shows a bamboo shark embryo cease gill movements in response to an electrical stimulus. In a research paper published here in PLoS One, scientists say sharks use highly sensitive electroreceptors to detect the electric fields emitted by potential prey. It appears some sharks can also use these electroreceptors to detect predators. The shark embryo reacts to the electrical stimulus by immediately ceasing gill movements - an innate avoidance response. Take a look:

The researchers, led by Ryan Kempster from the University of Western Australia, say in their report, "The cessation of gill movements is immediately followed by a rapid coiling of the tail around the body, with little or no discernible body movement during exposure ('freeze' response). Vertebrates that exhibit a 'freeze' response to predators have also been shown to induce cardioventilatory responses, where they decrease their heart rate (bradycardia) to reduce predation risk. As a result, the length of time that an animal is able to respond is finite, as the need to breathe and pump oxygen around the body will eventually overcome the urge to remain still and undetected. Thus, the bamboo shark embryos tested eventually resume, albeit much reduced, gill movements whilst still being exposed to the predator-simulating stimuli."

Kempster said in a statement, "Despite being confined to a very small space within an egg case where they are vulnerable to predators, embryonic sharks are able to recognise dangerous stimuli and react with an innate avoidance response. Knowledge of such behaviours may help us to develop effective shark repellents."

More from Science Space & Robots