| Aldrovanda vesiculosa | |
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Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Order: | Caryophyllales |
| Family: | Droseraceae |
| Genus: | Aldrovanda |
| Species: | A. vesiculosa |
| Binomial name | |
| Aldrovanda vesiculosa | |
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| Distribution | |
| Synonyms[2] | |
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Aldrovanda vesiculosa, commonly known as thewaterwheel plant, is the soleextant species in theflowering plant genusAldrovanda of the familyDroseraceae. The plant captures small aquaticinvertebrates using traps similar to those of theVenus 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 ofrapid movement.
While the genusAldrovanda is now monotypic, up to 19 extinct species are known in the fossil record.[3][4][5] While the species displays a degree of morphological plasticity between populations,A. vesiculosa possesses a very low genetic diversity across its entire range.[5]
A. vesiculosa has declined over the last century to only 50 confirmed extant populations worldwide. These are spread across Europe, Africa, Asia, and Australia.[5] However, potentiallyinvasive populations exist in theeastern United States.[6] It is kept by hobbyists.
Aldrovanda vesiculosa is a rootlessaquatic plant. Seedlings develop a short protoroot; however, this fails to develop further and senesces. The plant consists of floatingstems reaching a length of 6–40 cm (2–16 in).[5][7] The 2–3 mm (1⁄16–1⁄8 in) trap leaves grow inwhorls 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 (4–9 mm (3⁄16–3⁄8 in) per day in Japanese populations[8]), so that in optimal conditions a new whorl is produced once or more each day.[citation needed]
The actual traps consist of two lobes which fold together to form a snap-trap similar to that of theVenus 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,[9][10] making it one of the fastest examples ofplant movement in thekingdom. This trapping is only possible in warm conditions of at least 20 °C (68 °F).[11] Each trap is surrounded by between four and six6–8 millimetres (1⁄4–3⁄8 in) longbristles that prevent triggering of traps by debris in the water.[citation needed]
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,[12] and its high affinity for mineral nutrients in water.[13]
The small, solitary whiteflowers ofA. vesiculosa are supported above the water by short peduncles which arise from whorl axes. The flower only opens for a few hours, after which the structure is brought back beneath the water forseed production. The seeds are cryptocotylar: thecotyledons remain hidden within the seed coat and serve as an energy store for the seedling. Flowering, however, is rare in temperate regions and poorly successful in terms of fruit and seed development.[5]
Aldrovanda vesiculosa reproduces most often throughvegetative reproduction. In favourable conditions, adult plants will produce an offshoot every3–4 cm (1+1⁄8–1+5⁄8 in),[14] resulting in new plants as the tips continue to grow and the old ends die off and separate. Due to the rapid growth rate of this species, countless new plants can be produced in a short period of time in this fashion.[citation needed]
Winter-hardyAldrovanda formturions as a frost survival strategy. At the onset of winter, the growth tip starts producing highly reduced non-carnivorous leaves on a severely shortened stem. This results in a tight bud of protective leaves which, being heavier and having released flotational gases, breaks off the mother plant and sinks to the water bottom, where temperatures are stable and warmer. Here it can withstand temperatures as low as −15 °C (5 °F).[15] In the wild,Aldrovanda turions have been observed to have a relatively low rate of successful sinking.[15] Those nutritious turions that fail to sink are then grazed by waterfowl or are killed by the onset of frost. In spring when water temperatures rise above 12–15 °C (54–59 °F), turions reduce their density and float to the top of the water, where they germinate and resume growth.[15] Non-dormant turion-like organs can also form in response to summer drought.[15]
Aldrovanda vesiculosa is the second most widely distributed carnivorous plant species, only behind members of the genusUtricularia, native toEurope,Asia,Africa, andAustralia.Aldrovanda is spread mainly through the movement of waterfowl: plants sticking to the feet of a bird are transported to the next aquatic destination on the bird's route. As a result, mostAldrovanda populations are located along avian migratory routes. Throughout the last century the species has become increasingly rare, listed as extinct in an increasingly large number of countries.[5] In the 1970s, carnivorous plant hobbyists introduced this species to small backyard ponds in theUnited States in the states ofNew Jersey,Virginia, and theCatskills ofNew York, and they may be a potentiallyinvasive species due to their effects on aquatic invertebrates.[6]
The waterwheel plant faces significant conservation threats related to habitat degradation and human-induced modifications. Residential and commercial development, along with agricultural and aquacultural activities, pose immediate risks to the species. The impacts of these activities on the plant's aquatic habitats are of particular concern.[1]
Across Europe, the species is confronted by several environmental challenges, as identified by the Commission of the European Union. Acidification, canalization, drainage, eutrophication, pollution, and various forms of habitat modification are highlighted as threats. These changes in the natural environment have the potential to disrupt the waterwheel plant's habitats and populations.[1]
While the extent and effects of illegal trade remain uncertain, it is believed that some illegal activities involvingAldrovanda vesiculosa may occur. This potential threat adds complexity to the conservation challenges faced by the species.[1]
A. vesiculosa prefers clean, shallow, warm, standing water with bright light, low nutrient levels, and a slightlyacidicpH (around 6). It can be found floating amongstJuncus,reeds, and evenrice.[citation needed]
The Waterwheel (Aldrovanda vesiculosa) thrives in a range of aquatic habitats, including small fens, peat-bog pools, billabongs, lakes, lagoons, and river deltas. It prefers oligo-mesotrophic and dystrophic systems with low nutrient levels. These plants are commonly found in shallow backwaters or the littoral zones of larger lakes, where they face less competition from other aquatic species and where water levels remain relatively stable throughout the growing season. The Waterwheel is highly intolerant of habitat degradation, and even minor changes in water chemistry can lead to local extinction.[1]
Aldrovanda vesiculosa was first mentioned and illustrated in 1691 byLeonard Plukenet, based on collections made inIndia. He named the plantLenticula palustris Indica. The modern botanical name originates from Gaetano Lorenzo Monti, who described Italian specimens in 1747 and named themAldrovandia vesiculosa in honor of the Italian naturalistUlisse Aldrovandi.[16] WhenCarl Linnaeus published hisSpecies Plantarum in 1753, the "i" was dropped from the name (an apparent copying error)[17] to form the modern binomial.[14]
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