Utricularia sandersonii (Bladderwort) growing amidst sundews. Utricularia sandersonii is one of a genus of around 227 species. These tiny carnivorous plants are part a genus noted for their trap doored bladders. The trap doors snap open to vacuum in tiny rotifers and protozoa (or larger prey, depending on the species) when the prey brushes against tiny trigger hairs. Utricularia sandersonii is native to South Africa where it grows on wet rock surfaces at 600 to 3600 ft. altitude.