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Lasers reveal oyster's heartbeat

20 Feb 2003

Scientists study the heartbeat of a mollusc using reflected laser light for the first time.

By analyzing laser beam reflections, researchers in Mexico have monitored the heartbeat of a mollusc for the first time. The team says its simple technique allowed them to study localized areas of an oyster's heart in real time and could be adapted to study the heartbeats of other animals, including mammals, in the future. (Meas. Sci. Technol. 14 317)

Researchers have previously used infrared light to study the heartbeats of other organisms. "Infrared techniques are limited by the absorbing properties of water," team member Pavel Ritto told Optics.org. "Our technique provides a wide range of possibilities and applications of physiological interest, for example studying a specific region of the heart such as a ventricle."

In addition to this versatility, Ritto's technique boasts a simple set up requiring no specialised optics. The team directs a 1 mm diameter beam from a red diode laser operating at 632 nm through a small hole in the oyster's shell. They collect the reflections using a fiber optic bundle, which carriers the light to a photodiode where the variations are analysed by a computer.

Ritto and colleagues put their apparatus to the test on 24 oysters, each around 7 cm in length with hearts approximately 4 mm in diameter. According to Ritto, the oyster was chosen because its heart is a good model for the human heart.

Two cases were studied: first when the oyster was surrounded by air and second when it was immersed in its natural habitat of salt water. By monitoring the variations in voltage seen by the photodiode, the team recorded a trace with regular peaks indicating the beats of the oyster's heart.

The traces show that the oyster's heartbeat slows significantly when it was in air. In salt water, the heart beats 11 times in 20 seconds but this fell to 10 times in 60 seconds when in air.

Ritto now plans to optimise the laser-beam reflection technique before looking at other molluscs. And could this technique be used to study the human heart? "I'm sure the laser beam reflection technique could be used to study the heartbeat of many animals, even mammals," he said. "It's a matter of improving the method and characteristics of the components."

Jacqueline Hewett is news reporter on Optics.org and Opto & Laser Europe magazine.

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