Plant and Garden

The Venus Flytrap (Dionaea, Drosera, and Aldrovanda) Eats Meat and Remembers

Flytraps show a clear example of plant memory. The plant knows if its hair has been touched, and remembers that for a few seconds. After a second touch happens during that time frame, the plant then closes.

The Venus Flytrap is a carnivorous plant native to subtropical wetlands on the East Coast of the United States in North Carolina and South Carolina.

There also appears to be a naturalized population of Venus Flytraps in northern Florida as well as an introduced population in western Washington.

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Dionaea 

Historically, the plant was also known by the slang term “tipitiwitchet” or “tippity twitchet“, possibly an oblique reference to the plant’s resemblance to human female genitalia. (You can not make this stuff up!)

The plant’s common name refers to Venus, the Roman goddess of love. The genus name, Dionaea (“daughter of Dione”), refers to the Greek goddess Aphrodite, while the species name, muscipula, is Latin for “mousetrap”.

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Waterwheel plant (Aldrovanda vesiculosa)

Dionaea is a monotypic genus closely related to the Waterwheel plant (Aldrovanda vesiculosa) and Sundews (Drosera), all of which belong to the family Droseraceae.

Given that Dionaea evolved from an ancestral form of Drosera (carnivorous plants that use a sticky trap instead of a snap trap) the reason for this evolutionary branching becomes clear. 

Drosera consume smaller, aerial insects, whereas Dionaeaconsume larger terrestrial bugs. Dionaea is able to extract more nutrients from these larger bugs.

This gives Dionaea an evolutionary advantage over their ancestral sticky trap form.



The first description of the Venus Flytrap came from Arthur Dobbs who wrote “The great wonder of the vegetable kingdom is a very curious unknown species of Sensitive. It is a dwarf plant. The leaves are like a narrow segment of a sphere, consisting of two parts, like the cap of a spring purse, the concave part outwards, each of which falls back with indented edges (like an iron spring fox-trap); upon anything touching the leaves or falling between them, they instantly close like a spring trap, and confine any insect or anything that falls between them. It bears a white flower. To this surprising plant, I have given the name of Flytrap Sensitive.


It was dated Brunswick, Jan. 24, 1760 while he was the North Carolina colonial governor,

The Venus flytrap is one of a very small group of plants capable of rapid movement, such as Mimosa pudica, the Telegraph plant, sundews, and bladdworts.

Carnivorous plants are generally herbs, and their traps the result of primary growth. They generally do not form readily fossilizable structures such as thick bark or wood. As a result, there is no fossil evidence of the steps that might link Dionaea and Aldrovanda, or either genus with their common ancestor, Drosera.

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Dionaea 

Carnivory in plants is a very specialized form of foliar feeding, and is an adaptation found in several plants that grow in nutrient-poor soil.

Carnivorous traps were naturally selected to allow these organisms to compensate for the nutrient deficiencies of their harsh environments and compensate for the reduced photosynthetic benefit.

Most carnivorous plants selectively feed on specific prey. This selection is due to the available prey and the type of trap used by the organism. With the Venus flytrap, prey is limited to beetles, spiders and other crawling arthropods. In fact, the Dionaea diet is 33% ants, 30% spiders, 10% beetles, and 10% grasshoppers, with fewer than 5% flying insects.

It catches its prey—chiefly insects and arachnids—with a trapping structure formed by the terminal portion of each of the plant’s leaves, which is triggered by tiny hairs on their inner surfaces.

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Dionaea 

When an insect or spider crawling along the leaves contacts a hair, the trap prepares to close, snapping shut only if another contact occurs within approximately twenty seconds of the first strike.

Triggers may occur if one-tenth of the insect is within contact. The requirement of redundant triggering in this mechanism serves as a safeguard against wasting energy by trapping objects with no nutritional value, and the plant will only begin digestion after five more stimuli to ensure it has caught a live bug worthy of consumption.

The mechanism by which the trap snaps shut involves a complex interaction between elasticity, turgor, and growth. The trap only shuts when there have been two stimulations of the trigger hairs; this is to avoid inadvertent triggering of the mechanism by dust and other wind-borne debris.

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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 is generated, which propagates across the lobes and stimulates cells in the lobes and in the midrib between them.

It is hypothesized that there is a threshold of ion buildup for the Venus flytrap to react to stimulation. After closing, the flytrap counts additional stimulations of the trigger hairs, to five total, to start the production of digesting enzymes.

The acid growth theory states that individual cells in the outer layers of the lobes and midrib rapidly move 1H+ (hydrogen ions) into their cell walls, lowering the pH and loosening the extracellular components, which allows them to swell rapidly by osmosis, thus elongating and changing the shape of the trap lobe.

Alternatively, cells in the inner layers of the lobes and midrib may rapidly secrete other ions, allowing water to follow by osmosis, and the cells to collapse. Both of these mechanisms may play a role and have some experimental evidence to support them.

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Dionaea 


Flytraps show a clear example of plant memory. The plant knows if its hair has been touched, and remembers that for a few seconds. After a second touch happens during that time frame, the plant then closes.

If the prey is unable to escape, it will continue to stimulate the inner surface of the lobes, and this causes a further growth response that forces the edges of the lobes together, eventually sealing the trap hermetically and forming a “stomach” in which digestion occurs.

The release of digestive enzymes is controlled by the hormone jasmonic acid, the same hormone that triggers the release of toxins as an anti-herbivore defense mechanism in non-carnivorous plants. Once the digestive glands in the leaf lobes have been activated, digestion is catalysed by hydrolase enzymes secreted by the glands.

Digestion takes about ten days, after which the prey is reduced to a husk of chitin. The trap then reopens and is ready for reuse.

The “snap trap” mechanism characteristic of Dionaea is shared with only one other carnivorous plant genus, Aldrovanda. For most of the 20th century, this relationship was thought to be coincidental, more precisely an example of convergent evolution. Some phylogenetic studies even suggested that the closest living relatives of Aldrovanda were the sundews.

It was not until 2002 that a molecular evolutionary study, by analyzing combined nuclear and chloroplast DNA sequences, indicated that Dionaea and Aldrovanda were closely related and that the snap trap mechanism evolved only once in a common ancestor of the two genera.

Cephalotus Folliculari Carnivorous VERY RARE

A 2009 study presented evidence for the evolution of snap traps of Dionaea and Aldrovanda from a flypaper trap like Drosera regia, based on molecular data.

The molecular and physiological data imply that Dionaea and Aldrovanda snap traps evolved from the flypaper traps of a common ancestor with Drosera.

Pre-adaptations to the evolution of snap traps were identified in several species of Drosera, such as rapid leaf and tentacle movement. The model proposes that plant carnivory by snap trap evolved from the flypaper traps, driven by increasing prey size.

Bigger prey provides greater nutritional value, but large insects can easily escape the sticky mucilage of flypaper traps; the evolution of snap traps would prevent escape and kleptoparasitism (theft of prey captured by the plant before it can derive benefit from it), and would also permit more of a complete digestion.

In 2016, a study of the expression of genes in the plant’s leaves as they captured and digested prey was published in the journal, Genome Research. The gene activation observed in the leaves of the plants gives support to the hypothesis that the carnivorous mechanisms present in the flytrap are a specially adapted version of mechanisms used by non-carnivorous plants to defend against herbivorous insects.

In many non-carnivorous plants, jasmonic acid serves as a signaling molecule for the activation of defense mechanisms, such as the production of hydrolases, which can destroy chitin and other molecular components of insect and microbial pests.

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In the Venus flytrap, this same molecule has been found to be responsible for the activation of the plant’s digestive glands.

A few hours after the capture of prey, another set of genes is activated inside the glands, the same set of genes that is active in the roots of other plants, allowing them to absorb nutrients.

The use of similar biological pathways in the traps as non-carnivorous plants use for other purposes indicates that somewhere in its evolutionary history, the Venus flytrap repurposed these genes for the purpose of carnivory.

Propagation of Venus Flytrap

Plants can be propagated by seed, taking around four to five years to reach maturity. More commonly, they are propagated by clonal division in spring or summer. Venus flytraps can also be propagated in vitro using plant tissue culture.

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Most Venus flytraps found for sale in nurseries garden centers have been produced using this method, as this is the most cost-effective way to propagate them on a large scale. Regardless of the propagation method used, the plants will live for 20 to 30 years if cultivated in the right conditions.

Conservation Notes:

The species is classified as “vulnerable” by the National Wildlife Federation. In 2015, there were estimated to be fewer than 33,000 plants in the wild, all within 75 miles (121 km) of the city of Wilmington, North Carolina, and all on sites owned by The Nature Conservancy, the North Carolina state government, or the US military.

In 2014, the state of North Carolina passed Senate Bill 734 which classifies the theft of naturally growing Venus flytraps in the state as a felony. Tougher sanctions and penalties for the theft were also enacted on December 1, 2014, in accordance with legislation.

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extract

Venus flytrap extract is available on the market as an herbal remedy, sometimes as the prime ingredient of a patent medicine named “Carnivora”.

According to the American Cancer Society, these products are promoted in alternative medicine as a treatment for a variety of human ailments including HIV, Crohn’s disease and skin cancer, but “available scientific evidence does not support the health claims made for Venus flytrap extract”

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