Insects that have consumed metals, like cadmium, have been shown to poison the carnivorous plants that prey on them. Image credit: llamnudds/Flickr
When we think about pollutants moving their way up the food chain, we picture a process that begins with plants or plankton and gradually compounds until it reaches species at the top—like polar bears or humans.
Through habitat loss, illegal poaching, and pollution, carnivorous plans worldwide have suffered an alarming decline in population. In fact, the rate of decline has been so sharp, that researchers believe those factors cannot be solely responsible.
In search of another possible cause, Iain Green and Christopher Moody found that some metals, like cadmium, act as powerful toxins when consumed by carnivorous plants.
Research showed cadmium-tainted maggots poisoned Sarracenia leucophylla (pictured). Image credit: alexlomas/Flickr
To test whether ingesting metals had an impact on the health of carnivorous plants, the researchers fed Sarracenia leucophylla—an endangered species of pitcher plant—with house fly maggots contaminated with copper and cadmium. Copper is a beneficial metal for plants while cadmium is known to be toxic.
The plants that consumed copper-contaminated maggots had no trouble processing the metal. Researchers noticed, however, that for the plants consuming cadmium-contaminated maggots, the metal accumulated in their stems, inhibiting growth.
Would pitcher plants be safer on a diet of mice?
The Case of Cadmium
Cadmium was once a popular additive in fertilizers, metal coatings, and many other products. Though it is still used in batteries, some solar panels, and cigarettes, most cadmium pollution in the environment comes from the improper disposal of consumer waste—particularly e-waste—and the burning of municipal waste.
While it is similar in many ways to zinc—an essential metal for many biological functions—cadmium accumulates faster, acts as a carcinogen, and is toxic to plants and animals. It's similarity to zinc makes it readily absorbable in the environment—and very difficult to remove once contamination has occurred.
Even powerful metal jaws—it turns out—wouldn't help carnivorous plants swallow their metal-laden meal.
Read more about carnivorous plants:
Horrifying Plants That Eat the Living (Slideshow)
The Training of the Shrew: Pitcher Plant Evolves Into Toilet
Giant Rat-Eating Plant Discovered in the Philippines
Carnivorous Gadgets Eat Bugs and Mice for Charging Up (Video)