Mosquitoes are eating people and plastic, bringing materials up the food chain
Wednesday, September 26, 2018
As humans, we often think of mosquitos as blood-sucking parasites that do nothing but buffet lunch on us, cause us pain and irritant to our skins, and leave us itching and sometimes bloody when we squash them between our hands. But, the little flying blood buzzards are more than that, including plastic-ingesting insects that are polluting their own bodies while they gnaw on the man-made material and bring it up the food chain.
Authors of a paper — published in The Royal Society journal Biology Letters —found that when a mosquito larva eats microplastic, that plastic can remain in the insect's body into adulthood. So, the microplastic can then be transferred to whatever might eat that mosquito, including birds.
The process starts when mosquito larvae grow up in water contaminated with plastic accumulate the litter in their bodies. The mosquitoes may exacerbate the problem of plastic contamination when they are eaten by animals living on land.
The British researchers said they conducted their study in a lab, but they say it's not beyond comprehension to imagine that such bits of plastic could move up the food chain in this way.
"The implication is that you can have plastics at the bottom of the pond that are now going up into the air and being eaten by spiders and bats and animals that normally wouldn’t have access to that plastic," author Amanda Callaghan at the University of Reading in England told The Independent.
The microplastics used in the study were small latex beads. The authors said that smaller beads transfer more easily than larger beads into the mosquito's adult stage.
"Our study was a proof of concept in the laboratory," Callaghan told USA Today. "One of the next steps will be to sample lakes with plastics and mosquitoes to measure this."
Microplastic is common in waterways worldwide, and even arctic ice has a record amount of the pollutant. Birds, fish and other animals living around aquatic systems can ingest small plastic pieces by accident.
"These microplastics, with a diameter under 5 millimetres, pose a huge threat to the health of marine and freshwater ecosystems as they enter the food web."
Callaghan’s team fed 150 aquatic mosquito larvae with a mixture of food and microplastic beads of different sizes. They examined 15 individual insects selected at random while the animals were still in the larval stage, and they looked at another 15 individuals when the animals had turned into flying adult mosquitoes.
The team found microplastics in all 30 insects and larva contained, on average, more than 3,000 2-micrometer-wide beads. As the insects matured they gradually stopped consuming microplastics and excreted most of them, but Callaghan said they still counted about 40 beads, on average, in adults.
The team suggests that this could be a new pathway for the dispersal of plastic, as mosquitoes might act as a vector for transferring aquatic microplastics into the guts of the birds and bats that eat insects. "Any organism that feeds on terrestrial life phases of freshwater insects could be impacted by microplastics found in aquatic ecosystems," she says.
In an effort to reduce microplastics, some countries, including areas of the U.S. and the U.K., have banned microbeads found in toothpastes, face scrubs and shower gels.
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