The Bene Gesserit have their order. The navigators have their Guild. The Imperium has the Great Houses. These three orders form a triumvirate that controls the destiny of all Humanity in the Duniverse. Yet all would be completely at the mercy of the Arrakean sandworms, should they form a union. The Shai-Hulud make the spice, they make the Navigators who they are, they make the Bene Gesserit who they are, they indirectly make the Fremen who they are, and they even make Arrakis what it is. Could such a creature even exist, however? Biologist Sibylle Hechtel, Ph.D., responds to that very question .
Truth is stranger than fiction, but it is because Fiction is obliged to stick to possibilities; Truth isn’t.
—MARK TWAIN
Truth is stranger than fiction; fiction has to make sense.
—LEO ROSTEN
S HAI-HULUD’S NAME strikes fear in the hearts of Dune’s people.
The giant sandworm can swallow a harvesting machine, including its workforce of twenty-six men, in one gulp. Workers who harvest the priceless melange employ “carry-all” helicopters to swoop down from the sky and whisk them away before the dreaded sandworm can eat the harvesting machines (workers included). On Paul’s first trip into the desert, he watches from the helicopter as a worm takes a crawler:
A gigantic sand whirlpool began forming.… Sand and dust filled the air for hundreds of meters around it … a wide hole emerged from the sand. Sunlight flashed from glistening white spokes within it. The hole’s diameter was at least twice the length of the crawler … the machine slid into that opening … the hole pulled back. (Dune 123)
Worms range in size from a small specimen, 110 meters long and 22 meters in diameter, to medium worms at about 200 meters long, to the biggest worms at over 400 meters long with an 80-meter diameter mouth. Herbert leaves much of the worm’s biology vague, such as whether it is a vertebrate, how it moves or what it eats, and instead focuses on the worm’s behavior and actions and their effect on Dune’s population.
Herbert never describes precisely how the worm moves, only that it looks like a fish that “swims” just under the surface. He frequently describes the worm’s motion in sand as “a cresting of sand,” or mentions the “burrow mound of a worm” (Dune 414). The worm primarily comes above the surface when it’s eating a ’thopter or crawler, or when the Fremen catch one and put their hooks in its scales to drive it up out of the sand. He describes the worm as eating harvesting machinery and ornithopters, complete with occupants. What it may eat when underground, far from human habitation, Herbert leaves to our imagination. Of the sandworm’s lifecycle, Herbert mentions:
The circular relationship: little maker to shai-hulud; shai-hulud to scatter the spice upon which fed … sand plankton; the sand plankton growing, burrowing, becoming little makers [sandtrout]. (Dune 497)
He describes sand plankton that grow into sandtrout, some of which grow and eventually metamorphose into new sandworms. But he does not explain whether the sandworm lays eggs to create the sand plankton, whether there are male and female worms, or how reproduction occurs.
I will discuss which of the sandworm’s characteristics seem plausible in terms of what we know of terrestrial life, which attributes could not occur by any mechanism we know of on Earth, and how the sandworm could instead carry out certain functions in light of terrestrial biology. I’ll speculate on certain factors that Herbert leaves vague, such as what do all those sandworms eat, and where does the food grow?
Why don’t we see large sandworms roaming the Sahara or Chile’s Atacama Desert, the driest desert in the world with places where no rain has ever been recorded? When we explore other planets, might we find creatures resembling Dune’s sandworm? Possibly.
Let’s look at the worm’s life cycle and ecology to see how closely Shai-hulud fits with terrestrial animals. Liet-Kynes, His Imperial Majesty’s Planetologist and Arrakis’s planetary ecologist, predicted the existence of an underground organism like the sandtrout, because some organism must produce oxygen. Since very, very few plants grow above ground to generate oxygen, there must be some oxygen-producing life form underground. (Plants produce most of Earth’s oxygen. Before the evolution of photosynthetic plants, Earth’s atmosphere consisted of carbon dioxide, hydrogen, nitrogen, and methane, with little or no free oxygen.)
Kynes says:
How strange that so few people ever looked up from the spice long enough to wonder at the near-ideal nitrogen-oxygen-CO2 balance … in the absence of plant cover … something occupies that gap. I knew the little maker was there, deep in the sand, long before I ever saw it. (Dune 274)
Terrestrial life requires carbon, water, and an energy source. Photosynthetic plants take in carbon dioxide and water, using energy from the sun (photons) to split water and convert carbon dioxide (CO2 ) into carbohydrates—a long chain composed of carbon, hydrogen, and oxygen. They release waste oxygen (from the carbon dioxide, which has two oxygens for one carbon) into the atmosphere, providing us with the air we breathe. Scientists postulate that the early atmosphere consisted primarily of CO2 and methane (CH4 ) until the advent of photosynthetic plants to convert CO2 into free oxygen.
If the sandtrout generates oxygen, what would it use as an energy source? On Earth, chemoautotrophic bacteria use chemicals, usually hydrogen sulfide (H2 S), to supply the energy to synthesize carbohydrates from CO2 , similar to plants, and release oxygen. Since the sandtrout live deep underground, away from the sun and any means of photosynthesis, they would have to use chemicals, most likely H2 S, to supply their energy requirements. H2 S serves as an energy source for chemoautotrophic bacteria on Earth in deep-sea hydrothermal vents communities, some hot springs, and some caves. Since H2 S often escapes from underground vents formed as a result of volcanic activity, it’s the most likely source of subterranean energy on Dune.
What is the relationship between the sandworm and spice?
The pre-spice mass had accumulated enough water and organic matter from the little makers. … A gigantic bubble of Carbon dioxide was forming deep in the sand. (Dune 277)
Herbert describes the “little maker,” or “sandtrout,” as “a sandswimmer that blocked off water into fertile pockets within the porous lower strata” (Dune 497).
It’s plausible that the sandtrout themselves produce melange. Alternatively, they may tend an organism underground, most likely a fungus (which requires no light), that synthesizes melange. The sandtrout could prepare a suitable environment for the spice-producing organism by segregating and storing water. Herbert mentions no spice-producing organism other than the sandworm. But in terrestrial biology, plants, bacteria, and fungi produce the majority of exotic compounds, and we should consider this possibility.
We see “gardening” activities among ants. Leaf-cutting ants cut growing tree leaves and drag them to an underground growth chamber in their nest, keep it moist, and cultivate fungi on the leaves. The ants eat this fungus, which grows only underground in their nest. A second symbiotic bacterium grows on the ants and secretes chemicals, which protect the fungus from mold. Here the ants use antimicrobials to protect their harvest like we use insecticides in our fields (“Fungus”; “Leafcutter Ant”).
Plants synthesize numerous different “secondary chemicals” as a defense against parasites or herbivores. These thousands of secondary chemicals, so called because they’re not essential for the primary metabolism involved in growth, photosynthesis, and structural support, serve purely as a defense mechanism. Secondary plant compounds comprise alkaloids, cardiac glycosides, cyanide-containing compounds that can release cyanide when an insect tries to eat the plant, non-protein amino acids, and many others. Some well-known chemicals that plants synthesize to keep insects from eating them (not for our benefit) include the alkaloids such as cannabis, cocaine, opium, nicotine, caffeine, and digitalis (in foxglove). Other secondary plant chemicals work as antibiotics or to alleviate pain, like salicylic acid in willows (aspirin) or penicillin (a mold). Possibly either the sandtrout or the underground fungi produce spice to protect them against bacteria.
Other secondary compounds exist in marine snails and sponges (conotoxins), and Amazonian Indians have long used poison from toads (bufotoxin) to coat their lethal arrowheads. Chinese folk remedies prescribe a related extract from the skin of Asian toads. They ascribe life-prolonging attributes to these remedies, similar to the purported life-extending properties of spice, but in the case of Earth’s known plants with secondary chemicals, the life-extending effects have yet to be found. Existing terrestrial plants and animals both produce chemicals with activity similar to spice, in that they cause hallucinations and have other mind-altering properties.
The sandtrout block off water in underground pockets and could cultivate fungi deep below the surface, where they are safe from the arid, drying winds and from dehydration by the fierce sun. Herbert never specifies what the sand plankton and sandtrout eat, except possibly spice. But if he says that the sandworm produces the spice, how can the sandworm/plankton/trout simultaneously produce and subsist on melange? It makes more sense, in view of terrestrial biology, that another organism, like a fungus, grows underground and produces both oxygen and spice. The sandtrout could then consume the fungi, much like terrestrial leaf-cutting ants subsist on fungi in their underground nests, and either synthesize spice themselves or get it from the fungi. Hallucinogenic chemicals abound in mushrooms, such as psilocybin and the Amanita mushroom (Amanita muscaria ).
The diet of Shai-hulud is intimately connected with its life cycle. Let’s review Kynes’s description of both:
Now they had the circular relationship: little maker to pre-spice mass; little maker to shai-hulud; shai-hulud to scatter the spice upon which fed microscopic creatures called sand plankton; the sand plankton, food for shai-hulud, growing, burrowing, becoming little makers [sandtrout]. (Dune 497)
The sandtrout is a key element both in Shai-hulud’s continued survival and in spice production. The sandtrout encapsulates water pockets underground where fungi can grow; these, in turn, nourish both the sand plankton and more sandtrout. Herbert describes leathery scraps of material found with the spice mass after a blow. When the surviving sandtrout burrow down deep to encapsulate more water pockets from the residual water drops, the remains of the dead sandtrout can serve as additional food for the fungi.
We find similar ecologies deep beneath the sea in the ocean floor of the Galapagos Rift (more than 8,000 feet deep). Giant red tube worms (Vestimentifera) and various bivalves grow adjacent to hydrothermal vents. The volcanically active oceanic ridges create molten rock, which heats seawater, often to 700 degrees. These underwater “smoking chimneys” emit hot water, loaded with metals and dissolved sulfide, thus providing two of the main requirements for life—liquid water and an energy source.
In these sea-bottom communities, sulfide-oxidizing bacteria grow on rocks as mats and, in turn, limpets, clams, and mussels graze on the bacteria. However, many vent animals live with symbiotic bacteria. Tube worms have a specialized organ, the trophosome , with chambers that contain sulfide-oxidizing bacteria. The bacteria live in the tube worm’s trophosome, and the worms digest some of their symbiotic bacteria as a food source. Some bivalve mollusks have symbiotic sulfur-oxidizing bacteria in the gills (“Hot Vents”).
Imagine the sandtrout community as a combination of leaf-cutting ant nest and hydrothermal vent community. In underground caves or caverns, a vent or fumarole emits hot water laced with sulfur and minerals. The sandtrout sequester this water into chambers and pools. Alongside, the surviving sandtrout drag the scraps of their deceased brethren down to the nest where, on one side, bacteria consume sulfide and minerals and grow into large bacterial mats. In other chambers, spice-producing fungi grow on dead sandtrout scraps and dead bacterial mats. The sand plankton and sandtrout then devour some of the living fungi and bacterial mats.
Let’s look again at Kynes’s description of the life cycle:
They had the circular relationship: little maker to shai-hulud; shai-hulud to scatter the spice upon which fed … sand plankton; the sand plankton growing, burrowing, becoming little makers [sandtrout]. (Dune 497)
Probably the little maker (sandtrout), which collects and stores water and cultivates fungi, exists as the most abundant stage in terms of biomass. Initially, when sandtrout or sand plankton colonize a new cave, the sandtrout block off the water into pockets where the hypothetical fungi or algae grow. The sand plankton could then feed on the speculative underground bacteria or fungi that grow near vents. The sandtrout could grow and reproduce for many generations by budding, like some marine invertebrates including jellyfish, or by fragmentation, like ribbon worms.
Many organisms—bacteria, fungi, plants, and lizards—reproduce asexually (parthenogenesis) as genetically identical clones until the environment changes or deteriorates, which signals a switch to sexual reproduction. Exchanging genes between genetically different individuals creates new gene combinations, which might better adapt to the new, different environment. Some animals even switch sex to accomplish this, such as certain fish and amphibians (Rice).
The sandtrout could survive indefinitely as a clone form until some environmental change—like, perhaps, the accumulation of carbon dioxide resulting from the rampant growth of fungi and sandtrout (the pre-spice mass)—triggers sexual reproduction. If genetically different individual sandtrout mate, then they will lay eggs that hatch into individual sand plankton with novel gene combinations. When the pre-spice mass blows as a result of carbon dioxide accumulation (from the respiration of millions of sandtrout), the force would scatter the sand plankton (and spice) widely.
The giant sandworm comes to the spice blow, not necessarily only to eat spice, but also to help disperse its offspring to a new environment where they can colonize a new cave and survive to grow. Sand plankton and sandtrout cannot disperse across the desert over long distances unaided. When the spice mass blows, Shai-hulud scoops up as much of the plankton-laden sand as possible and takes its offspring to other caves. After colonization of a new vent and further reproduction, the sandtrout then lay numerous eggs, which hatch into tiny sand plankton that feed on spice, fungi, and sulfur-reducing bacteria. The sand plankton eventually grow larger and become sandtrout. A few of the (largest and most ecologically successful) sandtrout could grow into another sandworm:
The few survivors entered a semi-dormant cyst-hibernation to emerge in six years as small (about three meters long) sandworms … only a few avoided their larger brothers and pre-spice water pockets to emerge into maturity as the giant Shai-hulud. (Dune 497)
Insects, similarly, spend the majority of their life span in an immature feeding stage. Caterpillars, which are juvenile butterflies or moths, feed and grow all season and then molt and pupate, usually in a cocoon or enclosed burrow, during winter. A pupa doesn’t eat and, instead, remodels its body, using energy supplies accumulated during the feeding larval stage. It undergoes metamorphosis inside the protected pupal case over the inhospitable season, while food is unavailable, and emerges in spring as a butterfly or moth. Similarly, the sandtrout could form a cyst, hibernate, and emerge as a small sandworm. The smaller sandtrout would need to grow much larger by eating sufficient spice, fungi, bacteria, or other sandtrout to acquire enough biomass that it could turn into a three-meter sandworm. Remaining in hibernation, or a pupal stage, for six years is not unusual: seventeen-year cicadas, sometimes referred to as seventeen-year locusts, pupate and remain inactive for thirteen to seventeen years (Cicada Mania).
Biologists ascribe insects’ remarkable success, in part, to metamorphosis. This dramatic change of shape allows the adult more mobile form to exploit a very different environment from the juvenile form. For instance, caterpillars live in a narrowly circumscribed locale, feeding on leaves or fruit. In contrast, adults, like the Monarch butterflies, sip nectar from flowers and migrate almost a thousand miles from their wintering areas in Mexico to summer feeding grounds. One butterfly flew a 1,870-mile route from Ontario to Mexico in four months (“Voyagers”; “Metamorphosis”).
Not only insects metamorphose, changing form dramatically, but also marine animals. Cnidarians, which include jellyfish and the Portuguese man-of-war, alternate between two body shapes in their life cycles: a polyp, immobile stage, and a more mobile reproductive stage, the medusa (swimmer that looks like a jellyfish). Polyps often grow in colonies, reproduce asexually by budding (growing shoots, like plants), and look a little like sea anemones with a mouth on top, surrounded by tentacles. The medusa form, which we know as a jellyfish, grows much larger than the polyps (like the sandworm is much larger than the sandtrout), the largest jellyfish measuring more than two meters in diameter with tentacles about thirty meters long.
But sandworms aren’t insects or jellyfish!
A third group of organisms that undergo metamorphosis is amphibians—frogs and toads. Adult frogs lay eggs, in or near water, that hatch into tadpoles, which have gills and tails, eat plants, look a bit like fish, and live in lakes or streams. During metamorphosis to the adult form, the gills disappear; they absorb the tail and grow legs, and shift from eating plants to adopting a carnivorous diet. Not surprisingly, the amphibians that exploit either land or water in the very different adult and juvenile forms became the first successful vertebrates on land. Thus the sandworm’s metamorphosis from sand plankton to sandtrout to sandworm differs only in magnitude from the terrestrial model of metamorphosis. We see three highly successful kinds of organisms: insects, which go from land herbivore to airborne butterfly; Cnidarians, which go from sessile polyp to mobile, much larger medusa; and frogs, which transform from a vegetarian aquatic tadpole to a carnivorous frog. The sandworm, which starts as grazing plankton, grows into a vegetarian sandtrout, and then metamorphoses into the giant worm, fits in well with this model.
The adult giant sandworm accomplishes one more essential function—dispersal and colonization of new habitats. The small sandtrout, and even more so, microscopic sand plankton, can’t migrate long distances across sere desert sands. I would assume that on Dune, like on Earth, fresh volcanic rifts or fumaroles periodically appear in caves deep beneath the surface (“Fumarole”).
Assuming that Shai-hulud can smell the sulfurous gases emitted deep below the sand when it travels across the desert, it can head toward the new source of energy, burrow down, and leave behind some sand plankton or sandtrout to begin a new colony at the recently created volcanic vent.
One question that terrestrial scientists still debate is how marine organisms find and colonize the widely scattered ephemeral vents on the ocean floor. Colonizing newly formed volcanic vents below the sea could occur in three ways: (1) as a result of organisms drifting with ocean currents from an existing hydrothermal vent colony to a newly formed vent, (2) by organisms drifting down from surface waters where they floated on mats of floating seaweed, or (3) by organisms that were growing on a large fish or whale (barnacles sometimes grow on them) and that drifted down to the bottom when the fish or whale died. None of these methods of dispersal would readily work on Dune’s sandy deserts. Caterpillars have an adult form, the butterfly, which finds the widespread, patchily distributed clumps of plants or flowers its offspring prefer to eat, and then lays its eggs on those plants, ensuring that the next generation finds enough of the right food. Similarly, sandworms can distribute sand plankton to newly formed vents in underground caves. Herbert said, “Shai-hulud to scatter the spice.”
Marine scientists, however, remained unaware of ocean-floor hydrothermal vent communities until their discovery by the 1977 expedition to the Galapagos Rift. Herbert and Kynes would have been unaware of communities based around sulfur-gas emitting vents. Hence he would not have suggested that the sandworm would smell the sulfurous vents and head there to scatter its load of spice and sand plankton, much like turtles lay their eggs in fertile habitats, insects lay eggs on a juicy carcass, and salmon head upriver to spawn. Animals seek the best potential habitat for their offspring before they lay eggs or spawn.
Next, let’s look at how close terrestrial animals, both present and past, come in size. Dune’s sandworms range from medium worms of about 200 meters long, to half a league for the biggest, with an 80-meter-diameter mouth with which it can swallow a 120-by-40 meter harvester in one gulp. A league measured 1.5 Roman miles in ancient Rome and about 3.25 kilometers to 4.68 kilometers in France, so we’re looking at several kilometers in length!
What terrestrial animal does Shai-hulud most resemble? An earthworm, in the group “annelid” worms, which lives mostly in water or moist habitats. These and related worms lack an integument, or outer covering that resists desiccation—a must on a harsh desert world with Dune’s fierce winds.
Some arthropods, such as centipedes and millipedes, possess a hard exoskeleton, which covers their entire body and appendages. The exoskeleton prevents water loss, supports the tissue, and provides a place for muscles to attach. However, any animal with an exoskeleton will eventually outgrow its shell. It must then shed its old shell (molt) and wait for its new shell to harden. While this process is going on, the hapless worm would lose vast quantities of water from its body and remain vulnerable to high winds.
And last, an exoskeleton limits the ultimate size an animal can attain. A giant spider, like Aragog in Harry Potter and the Chamber of Secrets , would never grow large enough to menace Harry and his friends because of the limits an exoskeleton imposes on ultimate size. Nor will giant alien ants ever menace Earth. The sandworm cannot attain the size that Herbert postulates with an exoskeleton. In order to reach anywhere near the magnitude that Herbert suggests, the sandworm must be a vertebrate and more of a “sand snake.” At one point, Herbert mentions its “scales,” suggesting a more reptilian or snake-like creature.
Paul glanced down at the scaled ring surface on which they stood. … Bottom scales grew larger, heavier, smoother. Top scales could be told by size alone. (Dune 403)
Let’s consider the largest animals—extinct giant dinosaurs and modern-day whales. Both are vertebrates, with a support structure—the skeleton—on the inside. This internal skeleton, comprised of living tissue, grows larger as the animal grows and, thus, would not limit the ultimate size a sandworm could attain.
Dinosaurs, the largest of land animals, ranged from the twenty-meter long Apatosaurus , about 5 meters tall and weighing as much as five adult elephants, to the even longer Diplodocus , at almost 30 meters long. The giant Brachiosaurus and Titanosaurus , which may have been longer than thirty-three meters, were the largest animals that ever lived on land. Still, Shai-hulud dwarfs even the largest land animals.
What about whales? Blue whales are the largest animal ever found—bigger even than the dinosaurs. The largest whale weighed 171,000 kilograms and measured over 27 meters long. The longest whale was more than 33 meters long, but still a pygmy when compared with the sandworm.
Are there theoretical or practical limits to how large an animal can grow? In D’Arcy Wentworth Thompson’s monograph On Size and Form , he discusses the limits that physics places on specific animal and plant structures. Both animals and plants need to accomplish several tasks: they need to transport nutrients in, waste products out, protect themselves from predation, and successfully reproduce. The nutrients they require include food, water, and oxygen in the case of animals and carbon dioxide for plants. Waste products they need to remove, in addition to feces and urine, include waste heat generated by metabolic processes. When we use our muscles to exercise, such as when an animal pursues its next meal or runs to escape from a predator, muscles generate heat. In very cold weather, when our body temperature drops, we shiver to generate more heat, and in hot temperatures we sweat to get rid of excess heat. Heatstroke occurs when the ambient temperature and humidity are so high that we cannot remove the excess heat generated by activity, and our body temperature rises to dangerous levels.
The surface area of a body, such as a cylinder, cube, or sphere, increases as the square of the radius (r2 ) increases, whereas the volume of that same body increases as the cube of the radius (r3 ) increases, which means that as an animal’s size increases, the volume increases much faster than the surface area. As animals engage in strenuous activity, they generate heat as a function of the musculature and hence of volume. Normally the surface enables animals to efficiently lose heat, but with a larger volume-to-surface area ratio, larger animals will have a harder time disposing of extra heat.
Medium to large mammals, from dogs to humans to elephants, have various adaptations to help with thermoregulation. In order to dissipate excess heat, they pant (dogs) or sweat (humans). Biologists hypothesize that the elephant’s large ears serve as a type of radiator to facilitate heat loss. Also, herbivorous elephants don’t need to chase their food and, thus, generate less heat than predators like wolves! Anthropologists suggest that one factor contributing to man’s success as a hunter was his bare skin and sweat glands that allowed him to pursue his prey even on the hot savannah without succumbing to heat prostration.
How, then, would the much larger sandworm, with a scaly, water-impermeable or nearly impermeable integument, rid itself of excess heat generated from chasing prey? A time-honored method consists of evaporative cooling, allowing sweat on the body to help dissipate heat by the transformation of water to steam (water vapor; a phase change which requires an input of heat energy). However, using sweat as a method of cooling on Dune is clearly prohibitive. Perhaps this helps explain, in part, the “hot chemical furnaces churning inside the worm”—the sandworm cannot lose heat by any conventional terrestrial method, such as sweating, panting, or evapotranspiration, and instead accumulates the heat energy, generated by muscles during periods of high activity, and uses that heat to drive chemical reactions inside its body.
Physics further limits size structurally, such as the ultimate potential height to which trees can grow. Above a certain height, a tree will bend due to its own weight. An animal’s skeleton resembles, in principle, a beam supported at either end. Beams carrying no additional weight sag downward proportionally to the square of their length and cross-sectional size. Given two similar beams, one 5 centimeters long and the other two meters long, the longer sags 1,300 times as much as the shorter beam.
Applying this to terrestrial animals, we find that, as an animal’s size increases, its skeleton gets bulkier and heavier. Bones, as a percent of body weight, compose:
8 percent of the body of a mouse or songbird
13 to 14 percent of a goose or dog
17 to 18 percent of a man
In theory, up to 40 percent of a small sandworm. (Thompson 20)
To build a larger land animal, we need to use harder and stronger structural materials. The sandworm must have bones with a metal matrix instead of rock, like terrestrial animals (calcium, a chief constituent of bones, is heavy and breaks relatively easily). Imagine instead bones made of titanium, steel, aluminum, or a chrome-molybdenum alloy. These bones would be significantly stronger, thinner, and possess more tensile strength than our standard stony bones.
To support a 200,000 kilogram weight with a 100-meter-long bone requires a bone with a radius 0.5 meters, which would weigh about 155,000 kilograms, or more than three-quarters of the worm’s total body weight. Titanium “bone” only requires a radius of 0.3 meters, but titanium is heavier, so the weight of the titanium “bone” is still 136,000 kilograms. A “bone” made of carbon nanotubes would be only 0.17 meters in radius and weigh about 24,000 kilograms (“Carbon Nanotubes”; Dalton).
For a very sophisticated worm that can grow carbon nanotubes, the “bone” is 11 percent of the weight. For a titanium bone, it would be 40 percent, but then it’s unclear if the bone could support itself. Titanium bones would account for the sandworm’s rapacious appetite for harvesting machines! The complete human skeleton is replaced every ten years. For a worm that massive to replace its bone cells regularly, it would need to eat quite a few harvesters annually to meet its recommended daily requirement of heavy metals.
Dune’s sandworm is larger, by several orders of magnitude, than any terrestrial animals past or present. How does the sandworm compare in size with Earth’s largest plants? When Kynes crawled across the dunes, cast out by the Harkonnens without a stillsuit, he smelled a pre-spice mass in a pocket beneath him and thought of water:
He imagined it now—sealed off in a strata of porous rock by the leathery half-plant, half-animal little makers. (Dune 273)
He refers to the sandtrout, the immature form of the sandworm, as half-plant, perhaps to emphasize the unique and confusing nature of the beast. Let’s investigate how large plants can grow: the world’s largest tree (by volume) is the General Sherman Tree in Sequoia National Park, slightly over 1,487 cubic meters and 84 meters tall.
The world’s tallest tree was the 112-meter-tall Stratosphere Giant until it was replaced by a new candidate, a redwood in California’s Redwood National Park. According to Professor Steve Sillett of Humboldt State University, the record-setting tree, named Hyperion, measures 115 meters tall. Researchers exploring in the Redwood National Parks discovered two other redwoods taller than the Stratosphere Giant. Still, even at 115 meters, the tree is dwarfed by the worm.
Many biologists consider the world’s largest organisms to be either the giant “mushrooms” or aspen clones. Michigan biologists discovered giant fungal clones that cover an area of forty acres. Another group of scientists found a 1,500-acre fungus in Washington. We have no weight yet for this super-organism, which may be the world’s largest organism in area, but is not the largest in mass. Its discoverers guess that it probably weighs under 375,000 kilograms, less than a giant sequoia, which can weigh up to 2 million kilograms.
A fungus, Armillaria ostoyae , covered 600 hectares in Washington state. Mycology experts thought that if a monster Armillaria grew in Washington, then one as large could be causing trees to die in the Malheur National Forest of Oregon’s Blue Mountains. They found one that they estimated covered more than 2,200 acres (890 hectares) and was at least 2,400 years old.
Some scientists consider quaking aspen to be the world’s largest organisms: a stand of thousands of aspens is actually one single organism, which shares the same root system and has identical genes. The largest known aspen clone in Utah’s Wasatch Mountains contains 47,000 trees that cover about 106 acres (Grant). Scientists estimated that it weighs over 5.9 million kilograms, which makes it three times heavier than the General Sherman Tree sequoia tree and dwarfs even the giant fungi. While terrestrial animals come nowhere near Dune’s sandworm in size, some plants come close. Perhaps that is why Herbert calls the sandtrout half-plant—only plants can grow as large as the sandworm!
When we look at how animals disperse to colonize new habitats, we need to look at locomotion—how do these organisms move? Do they walk, crawl, swim, or fly? In the case of Shai-hulud, Herbert remains reticent about how the worm moves. (If I had to explain how a one-mile long creature walks or crawls, I too would be as vague as possible!)
Instead Herbert uses marine analogies. Kynes says one must avoid “tidal dust basins” which occur when:
Certain depressions in the desert have filled with dust over the centuries. Some are so vast they have currents and tides. (Dune 117)
When they saw the worm, there:
Came an elongated mount-in-motion—a cresting of sand. It reminded Paul of the way a big fish disturbed the water when swimming just under the surface. (Dune 118)
Later, Herbert says:
The worm came on like some great sandfish, cresting the surface, its rings rippling and twisting. (Dune 414)
Herbert describes the sandtrout as a “sandswimmer”—continuing in the vein of comparing Dune’s sands to the sea. He avoids an insoluble physical problem in portraying the sands of Dune as having properties similar to water. Earthworms burrow through the soil, but at an achingly slow pace. They actually “eat” their way through the dirt, in a way, by turning their mouth into a type of wedge.
The remarkable speed that Herbert ascribes to the giant sandworm wouldn’t be possible underground in a terrestrial type of medium. Instead, he gives Dune’s desert sands properties similar to water.
This solves further structural problems—if the sandworm lives in a buoyant, waterlike medium, then this medium helps support its mass and the sandworm can more easily grow to a larger size. D’Arcy Thompson mentions that for an animal immersed in water, its weight is counterpoised with the water around it and there no longer remains as great a physical barrier to indefinite growth. He further points out that in an aquatic animal, the larger it grows, the faster it goes. Its energy (for locomotion) depends on muscle mass (a function of volume), but its motion through water is opposed only by friction (a function of surface area), not by gravity, as on land.
However, if we assume that Dune’s sand acts like water, then we are faced with a contradiction, since the men of Dune can no longer walk the sands.
In conclusion, Earth could not support a terrestrial animal the size that Herbert ascribes to the sandworm. The largest dinosaurs, somewhat longer than 33 meters, were the largest animals to live on land. Even the largest whales are barely over 33 meters, as compared to the 200-meter sandworms. An aquatic animal could grow larger than a terrestrial one, since the water’s buoyancy helps support its weight. Also, in an aquatic medium it’s easier for animals to swim than walk; heat exchange is less of a problem since the worm can dispose of its excess metabolic heat directly into the water, which has a much higher heat capacity than does the land. (Heat capacity is a chemical property of matter. Water can absorb and store much more heat than land, which is why seaside climates are generally much milder than continental ones.)
The question of what produces the spice and generates oxygen remains vexing. On Earth, all oxygen production stems from plants, single-celled organisms like algae, and photosynthetic or chemosynthetic bacteria. No animal produces oxygen. Herbert states in the appendix that:
Even Shai-hulud had a place in the charts … his inner digestive “factory,” with its enormous concentrations of aldehydes and acids, was a giant source of oxygen. A medium worm (about 200 meters long) discharged into the atmosphere as much oxygen as ten square kilometers of green growing photosynthesis surface. (Dune 499)
On Earth, the only mechanism for a sandworm to generate oxygen would be if chemoautotrophic bacteria inhabited its gut, much like sulfide-oxidizing bacteria that live in the trophosome of tube worms at deep-sea vents (“Hot Vents”).
Thus, when we look for Shai-hulud on different planets, we may not find a sandworm in the Sahara or on Mars, but perhaps on Jupiter’s moon Europa (Irion), where it could swim the subsurface seas like some great Loch Ness monster.
SIBYLLE HECHTEL received her Ph.D. in biology from the University of California, Irvine. She taught the Biology of Aging at the University of Michigan while researching mitochondrial DNA evolution and later worked as a faculty research fellow at Caltech studying repetitive DNA. After several years of working sixty to seventy hours weekly in labs with no windows, she quit academics to work as a writer. Her work has been published in New Scientist, Red Herring, Reuters Health , and others. She wrote a book on rock climbing due out in 2007.
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