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As we know the planet dune is an empty desert, a huge territory with only sand and without any water or humidity.

There were no animals mentioned in the first books and I'm sure no plants could survive in the desert so I am wandering what do the worms eat to maintain their huge size.

Menelaos Vergis
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    They eat spice. The melange is raw spice processed through their digestive tract. The life-cycle of the worms is a completely enclosed loop. – Omegacron Jul 27 '15 at 13:58
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    They produce and eat spice at the same time? Then how would the humans gather the spice without leaving the worms starving? – Menelaos Vergis Jul 27 '15 at 14:17
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    Spice is what the worms decay into. If I get time I'll try to post a more detailed answer. But that question is exactly why the ecology of Dune is so vital to spice production. – Omegacron Jul 27 '15 at 14:31
  • i thought they ate the little spice plankton that gathered around and ate the spice, which made it appear as if the sandworms also ate spice. "Yeah, they eat sandplankton, which are a larval form of sandtrout which are in turn the larval form of sandworms. So they eat themselves." found this gem referencing the wiki. – Himarm Jul 27 '15 at 14:47
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    @Himarm - yep, that's right. They swallow the sand, spice & all, to digest the plankton, then poop out refined spice that's ready to collect & process. – Omegacron Jul 27 '15 at 15:10
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    It is not quite accurate to say "without any water". There is water, but it is so scarce that all organisms, including humans, if they want to be successful, sequester water. So lakes, rivers, oceans, no, but water yes. – Lexible Jul 27 '15 at 17:52
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    @Lexible - not only that, but they've evolved to the point that moisture of any significant volume is outright poisonous to the worms. This is the #1 reason why the spice cycle couldn't be transplanted to other planets. – Omegacron Jul 27 '15 at 20:40
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    They're 200 meters long with a hundred rows of teeth. The answer is "Whatever they damn well like". – Valorum Dec 09 '15 at 10:31

1 Answers1

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The sandworms of Arrakis are much like the whales of Earth, albeit with their own enclosed lifecycle & ecosystem. They "swim" through the sands and swallow entire pockets of spice to get at the plankton that dwell within. At the same time, however, the spice is produced by dying worms, which is what feeds the plankton. And the plankton that survive long enough eventually become worms. Dr. Liet Kynes described it thusly:

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 shaihulud, growing, burrowing, becoming little makers.

When a sandworm swallows a spice pocket, they get their sustenance from the plankton that live within it. The worm then excretes a more refined version of the spice, which is what the plankton eats. This also spreads the spice over the desert, allowing the lifecycle to perpetuate, thus leading to more plankton, more worms, more spice. This knowledge - and the ability to interrupt the cycle - is what gave Paul Atreides his leverage over the universe. Paul and his Fremen secretly planted

a water bomb over one of the major spice pockets. Detonating the bomb would release a large quantity of The Water of Life into the pocket, killing all of the plankton and little makers, causing a chain reaction across the planet which would end all spice production.

Omegacron
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    There seems to be a conservation of mass issue here. If people take the spice, it decreases the total worm+plankton+spice mass on the planet; how can this mass ever increase to prevent the system from being exhausted? – jwodder Jul 27 '15 at 15:57
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    @jwodder It's SciFi, apparently set in a world with different laws of thermodynamics. I recall Solyent Green had a similar problem. –  Jul 27 '15 at 16:11
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    @jwodder - you could say the same thing about any other natural resource. Once humans get involved, conservation becomes important or one day you'll run out of the resource. – Omegacron Jul 27 '15 at 16:35
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    @jwodder Presumably the system isn't so perfectly, precariously balanced that any amount of loss would destroy it. It's said that plankton feed on spice and shaihalud on plankton, but certainly energy and/or mass must enter and leave the system in other, less dramatic ways (e.g. what makes the pre-consumed spice less "refined" than the excreted form?). There must therefore be some margin within which extraction can occur without overharvesting, and there must also be some way to inject resources into the system. After all, the cycle must have started from nothing at some point. – talrnu Jul 27 '15 at 16:37
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    In the absence of any more detail than quoted, I would assume there are many more species of "sand plankton" than just the one that grows into little makers, and some of those other species are autotrophic. (N.B. I've only ever read the original Dune.) – zwol Jul 27 '15 at 17:39
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    @jwodder: People only harvest "spice blows" off the surface, and mostly from areas in the northern hemisphere which are near shelter from sandstorms. This is only a fraction of the total pre-spice masses, and there is a reservoir for re-population. – Clay Jul 27 '15 at 17:40
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    well as inputs there's energy from the sun and as for biomass there's all the people and harvesters getting eaten by worms. If the relationship was know by those profiting from the spice trade it should be possible to import any other foods the worms need to maintain the population. – Murphy Jul 27 '15 at 17:47
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    wasn't there a come sort of offhand comment in "God-Emperor" that adult worms were able to convert heat into energy? Leto mention is while shooting itself from a laser rifle. Also the little makers are part plant which means they are at least partially producers (organisms that produce biomass from inorganic material like carbon dioxide) which could explain the "disappearing mass" problem. – Yasskier Dec 09 '15 at 18:57
  • The pre-spice only turns into melange after a chemical reaction that takes place in sunlight on the surface. Presumably this is where energy is input into the system. – John Meacham Mar 07 '24 at 03:25