We're most familiar with carnivorous plants like the Venus flytrap, but scientists have recently discovered the worm-eating capabilities of a Brazilian plant -- not above ground as one might think, but through its sticky leaves that lay underground.
Found in the sandy, nutrient-poor soils of the tropical savannahs of Brazil, Philcoxia minensis is an uncommon plant that has tiny leaves which measure only a millimeter wide. Contrary to common sense, most of its leaves are below ground level, prompting scientists to investigate further. LiveScience quotes Rafael Silva Oliveira, a plant ecologist at the State University of Campinas in Brazil, as saying:
We usually think about leaves only as photosynthetic organs, so at first sight, it looks awkward that a plant would place its leaves underground where there is less sunlight. Why would evolution favor the persistence of this apparently unfavorable trait?
Making a connection between P. minensis' sticky leaves and the similar physiological traits of other carnivorous plants like Venus flytraps -- which developed their insect-eating habits due to their nutrient-poor habitat -- researchers tested their hypothesis by using tiny roundworms or nematodes.
Above: An electron microscope image shows the plant leaf surface, with nematodes and sand grains indicated by arrows.
The worm baits were loaded with the isotope nitrogen-15, which left a distinguishing residue on the plant's sticky leaves, indicating that the worms were digested by the plant:
Chemical analysis of the leaves that had been covered in nematodes revealed significant amounts of nitrogen-15, suggesting the plant broke down and absorbed the worms. The leaves also possessed digestive enzyme activity similar to that seen in known carnivorous plants, suggesting that the roundworms did not decompose naturally; the researchers speculate the leaves trapped the worms and then secreted enzymes that digested the worms.
It's amazing that even such an innocuous plant is quietly devouring worms underground. For more information, see the researchers' findings published online in the January 9 edition of Proceedings of the National Academy of Sciences, and on LiveScience.