Are Carnivorous Plants Turning Vegetarian?

A new study shows that certain carnivorous plants, known for quickly and cruelly trapping and killing tiny animals for food, may be turning vegetarian.

The aquatic carnivorous bladderwort, which can be found in many lakes and ponds worldwide, doesn't just acquire vital nutrients from eating meaty prey, but also by consuming algae and pollen grains.

"However, it remains unclear if these trapped particles are useless bycatch or whether they provide nutrients for the plant," the researchers wrote in the journal Annals of Botany.

To get to the bottom of this conundrum, an Austrian research group with the University of Vienna studied groups of bladderworts (Utricularia), one of the largest genera in carnivorous plants with over 200 species. By investigating the contents of over 2,000 traps, they found that only 10 percent contained animals, whereas 50 percent of the prey objects were algae. Additionally, more than one third of the prey consisted of pollen grains from nearby trees.

What's more, algae made up even more of the bladderwort's diet when these plants lived in nutrient poor habitats like in peat bogs.

In terms of algae, "they clearly provide other nutrients, possibly including phosphorus and trace elements," the study said. "By contrast, mosses, fungi and mineral particles appear to be useless bycatch."

Algae and pollen as well as animal prey differ in mineral nutrients as well as other compounds. During the study researchers found that those plants that ate both animals and algae were in the best shape; therefore, a well-balanced diet provides a wider range of nutrients.

Carnivorous bladderworts typically catch their prey with highly sophisticated suction traps and a valve-like trap door that opens and closes in a mere three milliseconds. Once inside the trap, the prey dies of suffocation and is degraded by digestive enzymes.

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