Nematode worms can learn to prefer plastic-contaminated prey over cleaner food
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Predators can learn to prefer eating prey that is contaminated with microplastics, even when clean food is available. This behaviour could have implications for the eating habits and health of entire ecosystems, including humans.
Researchers discovered this preference for plastic after studying the eating habits of small roundworms called nematodes (Caenorhabditis elegans) over several generations. When offered their usual diet of bacteria, as well as the same microbes contaminated with microplastics, the first generation of nematodes opted for the cleaner alternative. However, exposure to plastic-laced food over multiple generations altered their preferences.
โThey actually start to prefer contaminated food,โ says Song Lin Chua at Hong Kong Polytechnic University.
Why did the worms develop a taste for plastic? As creatures without true vision, nematodes rely on other senses to locate their food, such as smell. โPlastics may be part of those smells,โ says Chua. After prolonged exposure, they may recognize microplastics as โmore like foodโ and choose to eat them, he says. He speculates that other small animals that rely on smell to locate prey could โget confusedโ in the same way.
Chua points out that the behaviour is โmore like a learned responseโ than a genetic mutation, and therefore potentially reversible. โItโs more like a matter of taste,โ he says, likening the conditioning to a humanโs affinity for sugar. He says that, in theory, this could be reversed in future generations, but that it still warrants further study.
As one of the most common types of animals in the world, the nematodesโ dietary preferences could have much larger implications for the health of their ecosystems. โThose interactions of something eating something else are really important for recycling and transforming different forms of matter and energy,โ says Lee Demi at Allegheny College in Pennsylvania, who calls the discovery โalarmingโ.
โThis will pass down the food chain,โ says Chua, who notes the behaviour could create a kind of โripple effectโ that will also affect humansโ diets. โEventually it will still come back to us,โ he says.
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