National Geographic

A Thousand Worms Merge Into a Living Tower

What’s creepier than a worm rearing up on its tail to snag a passing insect? A thousand worms uniting into a single living, writhing, waving tower to snag a passing insect.

Pristionchus pacificus is a nematode or roundworm—one of 25,000 species that are among the most numerous animals on the planet. This particular nematode infests the bodies of scarab beetle larvae. It’s not a parasite as such, and its habits are positively tame compared to the creatures that often feature on this blog. It simply waits for its host to die of natural causes, and then eats the microbes that grow on its carcass.

But first, it has to get into a beetle. At some point during its early days, P.pacificus pauses its growth and becomes a dauer—an especially tough larva that’s adapted to survive through harsh conditions. The dauers stand on their tails and wave their body about in the hopes of latching onto passing beetles.

But Sider Penkov and Akira Ogawa from the Max Planck Institutes found that groups of P.pacificus can merge to form a single waving “dauer tower”, composed of up to a thousand individuals.

Each individual worm is just a quarter of a millimetre long but the towers can grow up to a centimetre. Some are so big that you can see them with the naked eye and photograph them with a macro lens, even though their members are all microscopic.

Such teamwork! Such togetherness! Such low odds of ever appearing on a motivational poster!

Other nematodes like C.elegans—that darling of biologists—also form dauer towers, but these constructions are small and fall apart easily. By contrast, P.pacificus’s towers are incredibly strong. Penkov and Ogawa tried prodding them with a metal wire, and they didn’t fall apart. They stuck the towers in water and the larvae started to swim, but they still kept together as a cohesive mass. The only thing that worked was a dash of detergent. When they added that to the water, and the towers disintegrate into a mass of individual larvae.

The team reasoned that the worms must be sticking together with a fatty or waxy chemical that repels water but can be dissolved by detergent. Indeed, they saw that the worms exuded small droplets over their skins, soon after they transformed into dauers. The droplets contained a huge wax molecule (C60H100O2N), one of the longest found in any animal or plant. The team called it nematoil.

Nematoil is the glue that gives the dauer tower its power. When the team synthesised the chemical and applied it to C.elegans, they found that even this nematode could unite into a sturdy spire.

Penkov and Ogawa suspect that the tower’s height gives its constituent larvae better odds of hitching onto a beetle. Once one of them snags some cuticle, the entire tower can get pulled along for the ride, held together by their nematoil secretions.

But their discovery raises many more questions. What brings the worms together in the first place? How do they coordinate their movements to produce a cohesive wave? And are there cheats?

P.pacificus reminds me of another microscopic creature called Dictyostelium discoideum, or Dicty for short. It’s not an animal but a slime mould. It mostly spends its time as single-celled amoebae, but these can merge into a many-celled slug. The slug slowly stretches skywards, forming a spore capsule atop a long stalk. Any amoebae that form the spores will survive, but those that create the stalk go nowhere and eventually die. This leads to conflict. Some amoebae are cheats, which make more than their fair share of spores and are rarely contribute to the stalk.

Does the same apply to P.pacificus? Do the nematodes at the base of the stalk perhaps get left behind? Do some of them secrete less nematoil (which, after all, takes a lot of energy to make), relying instead on their neighbours’ glue?

Reference: Penkov, Ogawa, Schmidt, Tate, Zagoriy, Boland, Gruner, Vorkel, Verbavatz, Sommer, Knolker, Kurzchalia. 2014.  A wax ester promotes collective host finding in the nematode Pristionchus pacificus. Nature Chemical Biology http://dx.doi.org/10.1038/nchembio.1460

There are 14 Comments. Add Yours.

  1. John
    March 7, 2014

    Fantastic writing! And super-cool subject :D
    Nice one Ed :]

  2. Paul Greathead
    March 7, 2014

    I think this is how multicellular life could have evolved. Similar tiny organisms working together, rather than some spontaneous split.

  3. Katie
    March 10, 2014

    Wonderful article. I just feel like I am a nerd now for reading it. LOL

  4. Jordan
    March 10, 2014

    Another proof that some insects are smarter than some humans

  5. Abu Banda
    March 10, 2014

    Wonder piece of a poem.this testifies the need for unite,n have very higher sense of tolerance tobe able to leave in a multi ethnocentric society.

  6. Juan Carlos
    March 10, 2014

    very impressive, but what’s more impressive is that this kind of strategy sounds very altruistic, and more in the P.pacificus. the ones in the “base” will not pass their genes.

  7. Daniel Dmello
    March 11, 2014

    I really enjoyed reading this.

  8. Hassan
    March 11, 2014

    That is fantastiç idea i think everything is thrôugh gradoul process.

  9. Motherof6
    March 11, 2014

    Thank you for sharing facts of our tiny, nearly invisible world. There are so many things we don’t know and can’t see that shows what a mighty powerful Almighty God we have that created our world. Man’s knowledge is not even a microscopic cell by comparison.

  10. sunil sahu
    March 11, 2014

    Nice pic

  11. Physicalist
    March 11, 2014

    Nematoil is the glue that gives the dauer tower its power.

    You just made my day. Love your writing.

    [Heh. Thanks! - Ed]

  12. Michael Day
    March 12, 2014

    Reminiscent of the Myxobacteria as well!

  13. Todd
    March 12, 2014

    Pretty cool!

  14. Richard
    April 1, 2014

    i just discovered Mr. Yong through a recent TED talk and i just gotta say, your writing helps me show how science is awesome to my friends

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