Dr Ravi Gooneratne
Position: Associate Professor, Lincoln University. Field: Agriculture and Life Sciences.
Dr Ravi Gooneratne is an Associate Professor in the Agriculture and Life Sciences Division at Lincoln University. He manages the Centre for Toxicology, where he carries out research projects as part of a team and writes articles for scientific journals.
Ravi Gooneratne working at his desk
Dr Ravi Gooneratne is an Associate Professor at Lincoln University in Canterbury. He is part of the Agriculture and Life Sciences Division.
He also teaches students about how toxins affect the physiology of animals. He has won a number of awards for his teaching and research, including the Lincoln University Teaching Excellence Award, the Lincoln University Special Achievement Award for Excellence in Research and the Creative Activity NZ Science Communicator Merit Award.
Dr Gooneratne examining a zebra
Dr Ravi Gooneratne treats a zebra. Ravi’s first degree was in veterinary medicine. He specialised in veterinary pathology, and it was from here he developed his interest in toxicology and the environment.
Ravi’s research interests include investigating how animals can be used to measure levels of soil or water pollution. One of Ravi’s projects investigates the levels of the liver enzyme (cytochrome p450) in salmon that live in South Island rivers. These enzymes in salmon (as in most animals) increase if they are needed to break down pollutants.
There is a direct relationship between the amount of this liver enzyme and the amount of a specific pollutant (polychromatic hydrocarbons) in the water. Therefore by detecting the amount of enzyme, the scientists can indirectly measure the amount of polychromatic hydrocarbons in the water and get an indication of the level of pollution from these chemicals.
Why use earthworms?
Dr Ravi Gooneratne, Lincoln University, describes why earthworms are the ideal research tool for measuring pollutants. Being in the soil, earthworms are often exposed to harmful chemicals, and they are found throughout the world. They also have a relatively well developed nervous system, and the electrical messages are easily picked up through their thin skin.
Another project that indirectly measures the amount of soil pollution was developed after Ravi visited a toxicology research centre at Iowa State University. In this case, Ravi developed a similar device to the one developed at Iowa State University and uses it for measuring the changes in electric current within earthworms.
Using controls
Dr Ravi Gooneratne (Lincoln University) describes several ways in which he uses controls in the experiments on soil pollution that he carries out. A good control enables him to be certain the effect he observes is a true effect rather than one caused by an outside influence such as temperature. Controls are very important in any experiment.
In all animals, nerves carry small electrical charges. When the worm is touched, the nerves send an electrical message down its body. The device Ravi is using measures how fast the nerves of worms conduct this very small amount of electricity that is passing through them. When worms live in soil that contains pesticides or heavy metals such as arsenic, their nerves are affected and do not conduct as fast as they do if they are in unpolluted soil. This technique can detect any changes in nerve function, which can be linked to the amount of soil pollution.
The advantage of using worms
Dr Ravi Gooneratne, Lincoln University, describes how using an organism to measure pollutants enables us to look at the effect a chemical has on living creatures rather than just the amount or type of the chemical. Not all chemicals are able to be absorbed by the body, or have an effect even if they are absorbed – this is called the bioavailability of the chemical.
In both these research projects, changes in the physiology of animals are used to measure soil pollution indirectly. This means the soil itself is not measured but the effect of the soil conditions on the functioning of animals is measured. To make the worm data valid and reliable, many worms are used. They are left in soil samples with known amounts of added pollutants, and the changes in electrical conductivity are measured after known time periods (weeks) to record an average. Then, the measurements are used to establish a standard or expected response in the known conditions. When farmers want their soil tested, the response of the worms in the farmer’s sample is compared with the response of worms in the known conditions.
Effect of pollution on electrical impulses
Dr Ravi Gooneratne, from Lincoln University, researches the conduction velocity of nerve cell impulses in earthworms and compares worms kept in polluted soil with those kept in clean soil. The response depends on the amount of the pollutant in the soil, how long the worm is kept in the soil and how much that particular pollutant affects the nervous system of the worm.
Ravi also supervised research student, Brian Patchet, who investigated how the toxins produced by fungi living inside grass leaves reduce the amount of grass eaten by grass grubs and weevils. These insects eat lots of grass and reduce the amount available to sheep. It is possible to increase the amount of fungi by coating the grass seeds with a solution containing the fungal spores.
When the seeds grow, the fungi then lives inside the grass leaves and produces chemicals that are toxic, which kill the grass grubs and argentine stem weevils that eat the leaves. There seems to be no short-term toxic or harmful effects on sheep from the chemicals made by the fungi.
Measuring electrical impulses
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.
Useful link
Link to the Lincoln University website.
This article is based on information current in 2008 and 2018.
