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By Meryl Ertelt

Trap Type:

Class: Equisetopsida
Subclass: Magnoliidae
Superorder: Caryophyllales
Order: Caryophyllales
Family: Nepenthaceae
Genus: Nepenthes
Species: Nepenthes rajah


There are two distinct plant genera that use the pitfall, or pitcher method, as a means to gain essential nutrients—the American pitcher plant and the tropical pitcher plant. The tropical pitcher plant, classified under the genus of Nepenthes, varies from its counterpart as it must capture prey via the formation of traps, or “pitfalls,” versus using its leaves as weaponry (Pavlovič, Masarovičová, & Hudák, 2007). With that being said, Nepenthes is colloquially referred to as “monkey cups,” as monkeys are occasionally spotted using the trapping basin for their beverages (Kew: Royal Botanic Gardens).

Examples of species in the Nepenthes Genus

The Nepenthes genus is geographically distributed within the Palaeotropics, spanning from Madagascar, eastward to New Caledonia, and southward to the western Pacific islands (Moran & Clarke, 2010). Atomically, their pitcher-like, photosynthetic leaf characterizes the genus—the leaf of the Nepenthes continues past the stalk, then curves, upwards and expands into an open basin. This chamber is then topped by a characteristic operculum—a flap that rises away from the mouth as the pitcher develops (University of California Museum of Paleontology, 2000). The pitcher is then attached to a vine by a looped tendril that develop from the tips of the blades (Moran & Clarke, 2010).

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Geographic distribution of the Nepenthes Genus

The pitcher of the Nepenthes is divided into three visibly discernable zones—a ribbed upper rim called the peristome, a waxy mid-section, and a basin that is filled with digestive fluid (Pavlovič, Masarovičová, & Hudák, 2007). The Nepenthes pitcher is further characterized by its dimorphism, that being its production of two distinctly different pitcher types. In this regard, young plants produce rosettes of “terrestrial” or “lower” pitchers that are characterized by a pair of vertically oriented, prey-guiding wings. As the Nepenthes grows, it produces a pitcher with an “aerial” or “upper” cylindrical funnel, that is rid of its previous guides (Moran & Clarke, 2010).

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Anatomy of the Nepenthes

The carnivory of the Nepenthes is a passive, gravity-driven process. The capturing of prey is facilitated by the peristome, which has a surface comprised of rows of overlapping epidermal cells aligned in radial ridges. These ridges capture prey via anisotropy—the individual cells overlap inwards, thus prey cannot maintain its grip—and via the wettability of capillary action—the rim is moistened by environmental factors, such as condensation or rainfall, or by the nectar produced at the inner rim of the peristome itself, thereby causing prey to lose traction and fall into pitcher (Moran & Clarke, 2010).

Upon the prey slipping from the peristome and entering the pitcher, it is faced with species-specific features that facilitate its demise within the pitcher’s chemical fluid. This fluid not only drowns the prey, but also allows for the enzymatic degradation of the prey, and thereby the uptake of nutrients. Further, the lower part of the inner pitcher wall possesses digestive glands, which carries out digestive, yet age-specific, functions. For example, in young pitcher's, the glands secrete an aqueous digestive fluid that contains a variety of enzymes such as proteases, peptidases, phosphatases, esterases, ribonucleases, and chitinases. In addition, young pitchers digestive glands also produce free radicals, as well as antibacterial and antifungal proteins to further aid in digestion. Once the pitcher has matured, the glands no longer secrete enzymes, but instead absorb the products of enzymatic breakdown in the form of amino acids, peptides, and ammonium ions (Moran & Clarke, 2010).

Nepenthes Rajah

Species Specific Geographic Distribution:

The Nepenthes Rajah is a pitcher plant that hails from Mount Kinabalu and Mount Tambuyukon in Sabah, on the island of Borneo. It is found at in a height between 1,500 and 2,600 meters above sea level, in a habitat of open grass with loose soil, such as that in landslip areas or ridge tops (Arkive).

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The Island of Borneo...
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...A closer look: Sabah, a Malaysian State...
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...An even closer look: Mt. Tambuyukon and Mt. Kinabalu.

Species Specific Anatomy:

The N. Rajah is a dicot, characterized by its massive nature. For example, its stem alone can grow up to 3 centimeters in diameter, and averages to be about 300 centimeters long, and up to 600 centimeters if allocated supportive and shady conditions. Further in line with the generas features, the pitcher parallels the massive nature of the stem—the leaf stalk ranges from 3.5 to 14.0 centimeters long, and the leaf blade, that being the pitcher, averages an area of 20 to 50 x 9 to 13 centimeters (Kew: Royal Botanic Gardens)

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The N. Rajah

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The N. Rajah
The N. Rajah’s pitcher is a leathery ellipsoid, and is described to be similar to the shape of a football. The peristome is characteristically wavy, and as in all Nepenthes, an operculum is held above the pitcher opening. The outside of the pitcher itself is a variation of red and purple, and the inside is anywhere from lime green to purple. Although seemingly secondary, flowers and fruit also exist on the N. Rajah. The flowers are brown and yellow in color, and give off a pungent odor, often described as a sugary fragrance. The flowers are also produced in large numbers of inflorescences, or flower clusters, that are usually 60 to 85 centimeters tall, however, male and female flowers are borne on separate plants. In regard to the N. Rajah’s fruits, they are uncharacteristically small, some 10 to 20 millimeters long, however are produced in large numbers (Kew: Royal Botanic Gardens).

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Peristome of the N. Rajah
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The N. Rajah Flower

Species Specific Carnivory:

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The N. Rajah retaining its prey

In line with the nature of carnivorous plants receiving its nitrogen not from the soil, but instead through a diet of insects, the N. Rajah consumes native insects and arthropods. To attract its prey, the N. Rajah has intense pitcher coloration, and produces a fragrant odor from its extra floral nectaries (Wells, Lakim, Schulz, & Ayasse, 2011). These nectaries cover the entirety of the pitchers; however cluster around the lower surface of the lid, thereby facilitating the first steps in the capture of the prey (Kew: Royal Botanic Gardens).

Once the prey is allured to the pitcher through the odorous nectar, and subsequently entered into the ellipsoid leaf basin, it is unable to grip the walls to escape due to a flaky wax that peels off as it struggles. Inevitably, the prey falls into the liquid, a combination of water and enzymes, stored at the bottom of the pitcher. To further retain the prey within the basin, the peristome, which in this species is a rigid, yet wavy, toothed edge, acts as a barbed wire fence, preventing the prey to reach safety (Kew: Royal Botanic Gardens).

The motion of the struggling prey stimulates the digestive glands of N. Rajah, so once the prey is drowned within the liquid in the lower half of the basin, the plant can begin its dinner. Eventually, the prey is broken down by the digestive enzymes, and transformed into nutrients that become available for the Nepenthes (Botanical Society of America).
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The N. Rajah's digestive fluids

The Myth of the N. Rajah: The Giant, Meat Eating Plant

“Audrey II” in Little Shop of Horrors, “the Saarlac” in Star Wars, “the vines” in the Ruins, “the pod plants” in Invasion of the Body Snatchers, “the trees” in Evil Dead, “The Doll’s Eye” in Minority Report, and every plant on earth in The Happening-- these movies, some classic, some modern, have contributed to the propagation of the idea of the existence of a deadly, carnivorous plant. Until recently, the N. Rajah was considered the closest real organism to these horrors—if one did happen to stumble upon these giant pitchers, they often contained the decaying carcasses of a rodent. The N. Rajah was thereby dubbed the world’s giant, meat-eating plant.

In 2010, Dr. Charles Clarke, an expert on carnivorous plants based at Monash University's Sunway Campus in Selangor, Malaysia, discovered that the N. Rajah is not the horror movie character it is made out to be, but rather a practitioner of coprophagia, that being an organism that ingests feces. He found that the N. Rajah has evolved to have a mutualistic relationship with the tree shrew, Tupaia Montana, and the rat, Rattus baluensis—these rodents feed on the plant nectar, defecate as a means to mark their feeding territory, and the plant catches and absorbs the feces as a means to ingest its required diet of nitrogen. This is particularly important due to the plants highland habitat where insects and other arthropods are often scarce; hence, remarkably, most of the N. Rajahs nitrogen is attained via this mutualistic relationship (Walker, 2010).
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N. Rajah and the tree shrew, a mutualistic relationship

This carnivory is again implemented through the use of attracting the rodents with the N. Rajah’s sweet, odorous nectar. Due to the evolution of this mutualistic relationship, the distance from the front of the pitcher's opening to the nectar glands mimics the exact head to body length of the mountain tree shrew (and thereby other small rodents). Hence, for the mutualistic interaction to take place, the rodent climbs onto the rim of the pitcher, and orients itself over the opening, towards the nectaries. As the rodent enjoys its meal, the basin acts as a latrine, however a latrine that digests its contents (Walker, 2010). Further, the fecal droppings then benefit the N. Rajah by triggering a cascade effect of prey attraction—with the fecal droppings mixed into the pitcher's slurry of water and digestive enzymes, the basin’s liquid, and not just the nectar, becomes attractive to surrounding insect prey (Wells, Lakim, Schulz, & Ayasse, 2011).

Such as one might think, this a rather precarious feeding ritual, and on occasion, the diner falls into the basin, and like insects, is unable to escape, and eventually drowns. The rodent is also eventually digested by the N. Rajah, however unlike the myth of the giant, meat-eating plant, feces and insects are the species desired food source, and most common. So, at least for now, we are safe from any carnivorous ecological threat.

Species Specific Human Interaction:

The N. Rajah is not a hugely beneficial plant to humans, and thereby has little substantive human interaction. Keeping that in mind, its two most common uses are that of being a marketing tool, as well as an object for ornamentation. In regard to its marketability, the N. Rajah has boosted tourism in its natural habitat, a rather unpopular vacation destination. As seen in Malaysian stamps and in promotional materials to support tourism in Sabah, and in particular in Kinabalu National Park in Borneo, the distinctive pitcher plant has facilitated, in a small way, economic growth for the region (Kew: Royal Botanic Gardens).

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The N. Rajah stamp
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A N. Rajah house plant

In regard to its ornamental use, the N. Rajah was introduced into cultivation in 1881, then fell out of the lime light for several decades, and upon its reintroduction in the 1970's, has remained in demand. However, legal specimens are hard to come by due to the N. Rajah’s conservation status as “endangered,” yet carnivorous plant enthusiasts can rest easier knowing that advances in tissue culture technology will continue to make the species more widely available (Kew: Royal Botanic Gardens).

Works Cited

Arkive. (n.d.). Pitcher plant (Nepenthes rajah). Retrieved April 16, 2013, from Arkive: http://www.arkive.org/pitcher-plant/nepenthes-rajah/image-G14239.html#speciesFactFile
Bonhomme, V., Pelloux-Prayer, H., Jousselin, E., Forterre, Y., Labat, J.-J., & Gaume, L. (2011). Slippery or sticky? Functional diversity in the trapping strategy of Nepenthes carnivorous plants. New Phytologist (191), 545–554.
Botanical Society of America. (n.d.). Carnivorous Plants / Insectivorous Plants. Retrieved April 13, 2013, from Botanical Society of America: http://www.botany.org/carnivorous_plants/
Kew: Royal Botanic Gardens. (n.d.). Nepenthes rajah. (M. Cheek, Ed.) Retrieved April 16, 2013, from Kew: Royal Botanic Gardens: http://www.kew.org/plants-fungi/Nepenthes-rajah.htm
Moran, J. A., & Clarke, C. M. (2010). The carnivorous syndrome in Nepenthes pitcher plants: Current state of knowledge and potential future directions. Plant Signaling & Behavior , 5 (6), 644-648.
Pavlovič, A., Masarovičová, E., & Hudák, J. (2007). Carnivorous Syndrome in Asian Pitcher Plants of the Genus Nepenthes. Annals of Botony , 100 (3), 527–536.
University of California Museum of Palenontology. (2000). Nepenthales. Retrieved April 14, 2013, from University of California Museum of Palenontology: http://www.ucmp.berkeley.edu/anthophyta/caryos/nepenthales.html
Walker, M. (2010, March 10). Giant meat-eating plants prefer to eat tree shrew poo. Retrieved April 16, 2013, from BBC: Earth News: http://news.bbc.co.uk/earth/hi/earth_news/newsid_8552000/8552157.stm
Wells, K., Lakim, M. M., Schulz, S., & Ayasse, M. (2011). Pitchers of Nepenthes rajah collect faecal droppings from both diurnal and nocturnal small mammals and emit fruity odour. Journal of Tropical Ecology , 27, 347–353.