Quick Dips

Earthworm Biosensors

For over 20 years, land pollution has been attracting a great deal of public interest, but finding out that it has been occurring and to what extent is still a challenge for scientists. Now earthworms may be coming to the rescue.

"What we are doing," says says Associate Professor Ravi Gooneratne from the Animal and Food Sciences Division at Lincoln University, "is working in a non-harmful, and a friendly way to detect and monitor environmental land pollution using the common earthworm as a biosensor."

Such a "biosensor" can be used to measure the biomolecular response that occurs when earthworms are exposed to environmental contaminants. Until now there has been no easy way to measure biochemical effects of environmental pollution on living organisms without causing pain or harm to the organism.

Measurements are taken of how earthworm's nerves are affected when exposed to soil pollutants and how quickly they recover when they are removed from the pollutants.

"What we do is take the earthworms that have been in a contaminated environment and measure the changes in nerve messages when worms are touched with a dangling rubber band (a tactile stimulus). The technique is similar to what happens when your doctor checks your nerves by tapping your knee with his little hammer," says Gooneratne.

Earthworms have a well-developed nervous system that is sensitive to very low levels of polluting chemicals, levels that are far too low to do physical harm. So this test can be used as an early warning indicator when potential pollutants are starting to rise in the soil. Action can therefore be taken much earlier than at present.

"Earthworms die when exposed to high levels of chemicals in soil and populations have already been affected in some polluted environments. This test will allow scientists to accurately monitor the land for soil pollution at a very early stage and also allow measurements to be taken during the recovery of land following remediation (cleanup)."

Such a technique could be of immense value in assessment of polluted sites, whether industrial, agricultural or another form of contamination. This could be used as a key screening test, which environmental protection agencies could adopt to evaluate contaminated sites.

"Now is the time to get serious about saving our land for our children."