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Mosquitoes may be contaminating ecosystems with tiny bits of plastic

Mosquito larvae are remarkably unfussy eaters. They glide through the ponds and puddles they live in, creating currents that draw tiny particles of food into their mouths—but miniscule plastic morsels can easily slip down the hatch as well. New research shows these “microplastics” stick around in the mosquitoes’ bellies even after they emerge from the water as flying adults, putting their land predators in danger of ingesting the contaminants.

To conduct the study, researchers poured small fluorescent yellow and green plastic beads about the size of red blood cells into water-filled beakers containing hungry mosquito larvae. Several days later, they fished the larvae out.

When the larvae grew up, the team spotted glowing beads inside their Malpighian tubules—structures equivalent to kidneys—confirming that microplastics can linger in an insect’s body even as it shifts from its larval to adult life stage. The researchers also found that the smaller the beads were, the more likely they were to wind up in the mosquitoes.

The findings, reported today in Biology Letters, indicate that after adult mosquitoes abandon the water (as shown in the image above), they can introduce the bits of plastic they ate as larvae into their new habitats. That means when nonaquatic predators—including birds, bats, and dragonflies—snack on mosquitoes, they may be in for an unhealthy dose of microplastics from the polluted waters in which their prey were born. Scientists already know microplastics can be toxic to many underwater animals. This newly discovered transport route may pose a threat to insect-eating species on land as well.