Aldrovanda vesiculosa, commonly known as the waterwheel plant, is the sole extant species in the flowering plant genus Aldrovanda of the family Droseraceae. The plant captures small aquatic invertebrates using traps similar to those of the Venus flytrap. The traps are arranged in whorls around a central, free-floating stem, giving rise to the common name. This is one of the few plant species capable of rapid movement. While the genus Aldrovanda is now monotypic, up to 19 extinct species are known in the fossil record. While the species displays a degree of morphological plasticity between populations, A. vesiculosa possesses a very low genetic diversity across its entire range. A. vesiculosa has declined over the last century to only 50 confirmed extant populations worldwide. These are spread across Europe, Africa, Asia, and Australia. However, potentially invasive populations exist in the eastern United States. It is kept by hobbyists. Morphology Aldrovanda vesiculosa is a rootless aquatic plant. Seedlings develop a short protoroot; however, this fails to develop further and senesces. The plant consists of floating stems reaching a length of . The trap leaves grow in whorls of between 5 and 9 in close succession along the plant's central stem. The actual traps are held by petioles which have air sacs that aid in flotation. One end of the stem continually grows while the other end dies off. Growth is quite rapid ( per day in Japanese populations), so that in optimal conditions a new whorl is produced once or more each day. Trap The actual traps consist of two lobes which fold together to form a snap-trap similar to that of the Venus flytrap, except that it is smaller and located underwater. These traps, which are twisted so that the trap openings point outward, are lined on the inside by a fine coating of trigger hairs, snapping shut in response to contact with aquatic invertebrates and trapping them. The closing of this trap takes 10–20 milliseconds, making it one of the fastest examples of plant movement in the kingdom. This trapping is only possible in warm conditions of at least . Each trap is surrounded by between four and six long bristles that prevent triggering of traps by debris in the water. Nutrient acquisition A. vesiculosa is able to grow in nutrient-poor habitats not only due to its carnivory, but also due to its ability to re-utilize nutrients from senesced shoots,