Aldrovanda
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''Aldrovanda'' is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of carnivorous plants encompassing one extant species ('' Aldrovanda vesiculosa'', the waterwheel plant) and numerous
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
. The genus is named in honor of the Italian naturalist Ulisse Aldrovandi, the founder of the Botanical Garden of Bologna, Orto Botanico dell'Università di Bologna.Genaust, Helmut (1976). ''Etymologisches Wörterbuch der botanischen Pflanzennamen'' ''Aldrovanda vesiculosa'' has been reported from scattered locations in Europe, Asia, Africa, and Australia.Kew World Checklist of Selected Plant Families, ''Aldrovanda vesiculosa''
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Description

The waterwheel is a small, free floating and rootless aquatic plant, with a length of about , and whorls of about in diameter. At every 3 to 4 cm the plant branches, sometimes forming offshoots. An average of 12 to 19 whorls spans the length of the plant, each with about 5 to 9 leaves, each up to 11 mm long. The growth is faster than terrestrial carnivorous plants, sometimes growing about 4 to 9 mm a day. In temperate regions the plant goes dormant in the winter, forming turions of about and sinking to the bottom. In tropical regions, the plant grows all year long without forming turions. The plant flourishes and produces seeds only in these warmer regions, with temperatures higher than , and produces only one flower, white or light pink, that arises above the surface. In temperate regions, the plant reproduces mostly via asexual means, producing inviable seeds or no flower at all. The leaf structure is very similar to the '' Dionaea'' (commonly known as the Venus flytrap), the main difference being air chambers present in the "stem". The traps, at the end of the leaf, contains up to 6 bristles, analogous to ''Dionaea'' teeth, that prevent debris from activating the trap. Each trap contains an additional 60–80 smaller "teeth", and circa 30–40 trigger hairs inside. The speed of closing is about 0.01 to 0.02 seconds.


Trap mechanism

The trap mechanism is akin to that present in ''Dionaea'' - Darwin even named it "the miniature aquatic Dionaea". The mechanism by which the trap snaps shut involves a complex interaction between elasticity, turgor and growth. In the open, untripped state, the lobes are convex (bent outwards), but in the closed state, the lobes are concave (forming a cavity). It is the rapid flipping of this bistable state that closes the trap, but the mechanism by which this occurs is still poorly understood. When the trigger hairs are stimulated, an
action potential An action potential (also known as a nerve impulse or "spike" when in a neuron) is a series of quick changes in voltage across a cell membrane. An action potential occurs when the membrane potential of a specific Cell (biology), cell rapidly ri ...
(mostly involving calcium ions—see calcium in biology) is generated, which propagates across the lobes and stimulates cells in the lobes and in the
midrib A primary vein, also known as the midrib, is the main vascular structure running through the center of a leaf. The primary vein is crucial for the leaf’s efficiency in photosynthesis and overall health, as it ensures the proper flow of material ...
between them.


Extinct relatives

The extinct species are known only from
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
and
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s, with the exception of ''A. inopinata'', which is also known from fossilised laminae. ''Aldrovanda'' was for a long time thought to be related to the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
form taxon '' Palaeoaldrovanda splendens'', but research published in 2010 suggests that remains attributed to ''Palaeoaldrovanda'' actually represent fossilised insect eggs.


Evolution

The organ of carnivory in ''Aldrovanda'' is the snap trap. Snap traps are only found in one other carnivorous plant genus, ''Dionaea''. The two genera have been shown to share a most recent common ancestor by analysis of combined nuclear and chloroplast DNA sequences. When sequences of chloroplast DNA of ''Aldrovanda'', ''Dionaea'', and ''Drosera'' were analyzed alone, however, ''Aldrovanda'' and '' Drosera'' (sundews) were shown to share a most recent common ancestor. It has been proposed that this discrepancy between gene trees based on nuclear and cytoplasmic DNA analyses can be explained by chloroplast capture, as similar inconsistencies have been explained by this phenomenon.


Conservation

''Aldrovanda vesiculosa'' is listed as “Endangered” on the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
. It is native to Europe, Asia, Africa, and Australia, but is considered extinct in much of its native range, primarily due to eutrophication. Despite being endangered in its native range, it was introduced in the U.S. and has been reported to be rapidly spreading in the waters of the
Catskill Mountains The Catskill Mountains, also known as the Catskills, are a physiographic province and subrange of the larger Appalachian Mountains, located in southeastern New York. As a cultural and geographic region, the Catskills are generally defined a ...
of New York, USA, where it is being evaluated as a potentially problematic
invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
.


Species

*†''Aldrovanda borysthenica'' *†''Aldrovanda clavata'' *†''Aldrovanda dokturovskyi'' *†''Aldrovanda eleanorae'' *†''Aldrovanda europaea'' *†''Aldrovanda inopinata'' *†''Aldrovanda intermedia'' *†''Aldrovanda kuprianovae'' *†''Aldrovanda megalopolitana'' *†''Aldrovanda nana'' *†''Aldrovanda ovata'' *†''Aldrovanda praevesiculosa'' *†''Aldrovanda rugosa'' *†''Aldrovanda sibirica'' *†''Aldrovanda sobolevii'' *†''Aldrovanda unica'' *'' Aldrovanda vesiculosa'' *†''Aldrovanda zussii'' Several undescribed species are also known. The distinctions between the various named species have been criticised, although SEM analysis of the seed structures seems to confirm the existence of different species.


References

{{Authority control Droseraceae Carnivorous plants of Asia Carnivorous plants of Europe Carnivorous plants of Africa Extant Paleocene first appearances