Rights: The University of Waikato Published 18 June 2008 Download

Dr Ravi Gooneratne, of Lincoln University, measures the effects of soil pollutants on earthworms, which slow the rate signals travel along their nerves. When you touch a worm, a tiny electrical impulse travels along its nerves. These are picked up by a special plate and an oscilloscope amplifies the signal so the time the nerve impulse takes to travel along the worm can be measured.


What we are looking at are the effects of the chemicals on the nervous system. When someone touches your finger, you know the electrical messages go from your finger along the nerves to the brain, and that’s how you’d know that someone has touched you. The speed at which the messages are sent are affected when the organism is exposed to things like metals, like copper and high levels of cadmium and lead, and arsenic – these are toxic pollutants – or even things like pesticides. So when I touch the worm at one end, it’s like somebody touching your finger. They’re like electrical messages that are going along, and this can be picked up by electrical wires on the wax plate that we use.

So we can connect any two of these wires to an instrument called an oscilloscope, which measures small electrical currents, so when the message that comes along reaches one of these, it sends an electrical message to our oscilloscope and then it goes along, and when it reaches the second one, it sends an electrical message, and our oscilloscope measures the timing between this message and this message. And we know the distance between these two electrical wires, so we can measure the rate at which these electrical messages are sent along these nerves.