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: