Plants hunting water-fleas

There are rootless aquatic plants living in clean waters called Utricularia. They are distributed worldwide, and two species also exist in Portugal.

The plant’s green structure is a very thin stem with leaves reduced to filaments. On these thin branches, we can find the utricles. These are round structures about a millimeter in diameter that act as traps for water fleas and other microscopic aquatic invertebrates. When prey touches the cilia of these traps, structured like the two halves of a shell, the trap opens very quickly, and through the vacuum effect, the prey is swallowed into the utricle.

This insectivorous feeding method provides nitrogen and other nutrients to this rootless aquatic plant. Once well-fed, the Utricularia has the strength to produce its reproductive organs, the flowers. These are much larger than any other part of the plant and are of great beauty, as shown in the photo.