Earthworms, look away now

by Matthew Cobb

Jerry sent me this link, which is to a video that has been seen a staggering 25,817,000 times. It’s pretty gruesome, even if you aren’t an earthworm:

As the title indicates, it’s taken from a BBC series called Wonders of the Monsoon, and features two annelids at war – an oligochaete (earthworm) being nommed by a hirudinid (leech).

Both these animals are members of the phylum Annelida, which means ‘small ring’. As you can see, they both have segmented bodies, in the shape of externally-visible rings.

Random oligochaete facts (add your own in the comments!): mainly terrestrial, some freshwater, very few aquatic. There can be tens of thousands of them in a square metre of soil. Most are detritivores (i.e. they eat decaying matter). They can be tiny (mm scale) to meters long. The name ‘oligochaete’ means ‘few bristles’ – if you put an earthworm on a piece of paper and listen carefully, you can hear the noise of the bristles scratching on the paper. And finally, there are no indigenous earthworms in Canada or the northern parts of the USA. During the last ice age that was no place for an earthworm to be, and the worms that are now there have been introduced by humans.

Random hirunidae facts (add your own in the comments!): they are found in all environments – terrestrial, aquatic and marine. They are either predators (like the one above) or suck blood. This ability led to them being used in medicine, right up until the mid-20th century.

If you want to know more about leeches, this book, by my friends and colleagues Rob Kirh and Neil Pemberton is excellent. You’ll also learn lots about how leeches have been viewed through history.


Probably the most famous leech-related scene in cinema is this, from Rob Reiner’s excellent Stand By Me (1986), featuring Wil Wheaton and River Phoenix:


  1. Posted September 26, 2017 at 9:04 am | Permalink

    I read something about a guy who swam in a stream in Nepal I think, & a leech took up abode in his nose, just out of reach…

  2. Posted September 26, 2017 at 9:07 am | Permalink

    In the version of this post that WordPress ate and I had to rewrite, you got the story of Daniela Liverani, who had a 7.5cm leech removed from her nose in Scotland upon her return from South East Asia: – MC

  3. Posted September 26, 2017 at 9:07 am | Permalink

    I’ll see your Wil Wheaton and River Phoenix and raise you a Humphrey Bogart and Katherine Hepburn: the most famous leech scene in cinema is from The African Queen.

    • Ken Kukec
      Posted September 26, 2017 at 9:10 am | Permalink

      I was just about to post a link to that myself. Think I will anyway:

      • Posted September 26, 2017 at 9:23 am | Permalink

        Yup, my bad. Reiner was obviously referencing this scene. – MC

      • busterggi
        Posted September 26, 2017 at 11:20 am | Permalink

        May as well go all in.

  4. Avis James
    Posted September 26, 2017 at 9:08 am | Permalink

    I showed the leech eating an earthworm video in my Zoology class yesterday! It is fun to watch the students faces!

    • Posted September 26, 2017 at 11:23 am | Permalink

      I wish I could teach Invertebrate Zoology. I would definitely show this video.

  5. Posted September 26, 2017 at 9:10 am | Permalink

    I will never look at spaghetti the same way again!

    • W.Benson
      Posted September 26, 2017 at 4:40 pm | Permalink

      Those leaches can really slurp down the worms.

  6. ThyroidPlanet
    Posted September 26, 2017 at 9:11 am | Permalink


  7. Joseph O'Sullivan
    Posted September 26, 2017 at 9:16 am | Permalink

    Worm fact: earthworms in the northern US are considered invasive. They change nutrient cycling. I have heard they have had negative effects on some wildflowers and salamanders.

    • Christopher
      Posted September 26, 2017 at 10:08 am | Permalink

      I’ve heard they may also be having a negative impact on Ovenbird (S. aurocapilla) populations, although I don’t recall why.

  8. kieran
    Posted September 26, 2017 at 9:28 am | Permalink

    Some species exhibit parthenogenesis.

  9. Posted September 26, 2017 at 9:35 am | Permalink

    Another nasty fate for earthworms is being eaten from the inside out by larvae of the cluster fly. The flies are very common in Nova Scotia -overwintering in swarms wherever they find shelter in crevices in window frames, behind shingles wherever emerging in the spring to mate and lay eggs on the soil. The larvae burrow into the soil and into a convenient earthworm to feed.
    Oh my.

    • Heather Hastie
      Posted September 26, 2017 at 1:29 pm | Permalink

      That God dude must have a pretty nasty mind to have created such creatures! What kind of person dreams up this stuff?

      • Posted September 27, 2017 at 3:20 pm | Permalink

        Oh dear, you likely have equally gruesome in NZ. I hear that the genome of every single one of those parroty things that ceiling cat delights in is being catalogued. You know the ones that land on sheep and strip muscle from around the backbone. Nobody promised us a rose garden-or did they? Did this kind of stuff happen in the garden of eden? Ignorance is bliss.

  10. Christopher
    Posted September 26, 2017 at 10:06 am | Permalink

    Searching for the book on Amazon turned up anti-leech hiking socks and a tube of balm made with medicinal leech extract. Take your pick

  11. Posted September 26, 2017 at 10:23 am | Permalink

    Another horrific predator of earthworms is the invasive New Zealand flatworm Arthurdendyus.

    • KiwiInOz
      Posted September 27, 2017 at 6:36 am | Permalink

      Check out our native Powelliphanta snails slurping down on earthworms, too.

  12. Jonathan Wallace
    Posted September 26, 2017 at 11:14 am | Permalink

    The annelids that I have always particularly remembered from undergraduate days are Chaetopterus and the Palolo worm. The former is a weird looking tube-dweller that makes a mucus bag that operates as a kind of fishing net to filter food out of the water flow it generates through its tube. The bag is periodically rolled up and ingested along with whatever it has captured. The mucus bag is an extremely effective filter, which my old text book informs me is capable of capturing particles as small as 4 nanometres diameter. Although it spends its life in an opaque tube Chaetopterus is strongly bioluminescent and I believe the function of this – if any – is unknown.

    Palolo worms are famous for their synchronised mass spawning events when the hind part of the worm rises to the ocean surface along with millions of others to release sperm and eggs. These events are predictable from the phases of the moon, combined with time of year and they are enthusiastically harvested as a delicacy by various peoples in different parts of the world.

    Chaetopterus and Palolo worms both belong to the third major group of annelids, the polychaetes (‘many bristles’).

  13. Posted September 26, 2017 at 11:27 am | Permalink

    The largest earthworm is the Gippsland earthworm of Australia, growing to 9 feet.

  14. Jo
    Posted September 26, 2017 at 12:10 pm | Permalink

    A drinking song featuring leeches

    Nay, start not from the banquet where the red wine foams for thee.
    Though somewhat thick to perforate this epidermis be;
    ‘Tis madness, when the bowl invites, to linger at the brink;
    So haste thee, haste thee, timid one. Drink, pretty creature, drink!

    I tell thee, if these azure veins could boast the regal wine
    Of Tudors or Plantagenet, the draught should still be thine!
    Though round the goblet’s beaded brim plebeian bubbles wink
    Twill cheer, and not inebriate. Drink, pretty creature, drink.

    Perchance, reluctant being, I have placed thee wrong side up.
    And the lips that I am chiding have been farthest from the cup.
    I have waited long and vainly, and I cannot, cannot think
    Thou wouldst spurn the oft-repeated call: Drink, pretty creature, drink!

    While I watch’d thy patient struggles, and imagined thou wert coy,
    ‘Twas thy tail, and not thy features, that refused the proffer’d joy.
    I will but turn thee tenderly – nay, never, never shrink
    Now, once again the banquet calls: Drink, pretty creature, drink!

    Carols of Cockayne by Henry Sambrooke Leigh 1837–1883

  15. pdx1jtj
    Posted September 26, 2017 at 1:32 pm | Permalink

    FWIW, leeches are still used in medicine.

  16. Gregory Kusnick
    Posted September 26, 2017 at 1:38 pm | Permalink

    A whole thread about earthworms with no mention of Darwin?

  17. Tom Czarny
    Posted September 26, 2017 at 3:41 pm | Permalink

    I’ll see your leech and raise you a Bobbit Worm:

  18. sleazel
    Posted September 27, 2017 at 9:33 am | Permalink

    When it comes to slithering slime I highly recommend the cult flic “Slither” which conflates Annelid and Molluscan reproductive techniques to create memorable monsters that act like leeches but look like giant orange banana slugs. These are the evil spawn of an alien overlord who rather resembles Cthulu, tentacles and all! Like the homunculi in Killer Klowns from Outer Space the alien evil travels by means of meteorite from planet to planet devouring all forms of life.

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