Everyone’s gotta eat.
Carnivores like a meaty burger.
Herbivores are salad fiends.
But do you know who really takes the cake?
If by cake you mean a grimy meal of dirty, nutrient-rich dead leaves and other forest
litter?
Detritivores: literally, trash eaters.
Well for today’s video, what you think of as "earthworms."
But these little subterranean monsters’ appetites give us the bountiful world that
allows us to farm food for our hungry omnivorous bellies.
The question is, how does Slimey turn dead plants, decomposing animal bits, weird fungi,
and even mold and manure into beloved compost?
Let’s take a chemical digestion journey, a straight shot from mouth to anus through
a munching earthworm’s gut.
Before we get to the chemistry, some biology and physics.
Earthworms are part of a superfamily of invertebrates called megadriles that have fascinated for
centuries.
Charles Darwin himself wrote his last book on the creatures.
As we said, worms process food in a straight shot: Their guts don’t twist and turn like ours.
Up front is a toothless mouth, then a series of muscles that suck detritus in.
Just after the earthworm mouth is a curious set of glands that secrete a milky liquid
containing calcium carbonate - the same stuff that makes up seashells.
The dirt where worms make their home has a lot of CO2 in it
which can mess up a worm’s body chemistry, making its blood more acidic.
So this gland is a nifty way for worms to balance out their CO2 with soil calcium, which,
by the way, means less CO2 makes it into the atmosphere.
Earthworms have a gizzard, too.
Where churning muscles crush the incoming food thanks to bits of sand and rock the earthworm
has "Hoovered" up.
Hey, you do what you can if you don’t have teeth but eat all kinds of crunchy stuff.
So the earthworm’s intestine receives some crushed dirt including plant bits like dead
leaves and bark that no human could hope to digest.
For us, a happy human gut is one that regularly has a bit of fiber pass on through.
But earthworms eat almost entirely fiber, so how do they get any nutrients?
Enter a quartet of enzymes: amylase, lipase, pepsin, and cellulase.
These specialized proteins chop and modify swallowed food into molecules the body
can take in.
We humans have three of these enzymes: amylase in our saliva breaks down starches.
Worms just happen to keep their spit in their guts.
Lipase breaks down fats so earthworms can digest plant oils.
Then pepsin breaks down proteins to digest animal bits.
But earthworms can make a dinner of all that vegetable-y fiber thanks to cellulase.
As its name suggests, this enzyme breaks down cellulose, the hard fiber that gives leaves
structure and lets trees stand tall with wood and bark.
Given enough time, no dead tree is a match for Slimey!
All forest litter is not a tasty dirt sandwich, however.
Many plants contain toxins that defend them from hungry creatures.
Polyphenols contain a class of toxic molecules that cause illness or death to insects.
But earthworms, who can’t avoid munching polyphenols up, have molecules in their gut
called drilodefensins.
It seems only soil-dwelling megadriles contain drilodefensins, which is why they can chew
right through those dead plants.
A few enzymes aren’t the only digestive trait we share with earthworms.
We both have gut bacteria showing just how tiny microbes are.
Not surprisingly, gut microbes in earthworms are soil bacteria that chew nitrogen out of
the plant material, taking in nitrates and nitrites and expelling nitrogen gas in a process
called denitrification.
Which leads us to consider what comes out in the end … of the earthworm.
Biologists call earthworm poop “castings”.
Given what happens in worms’ guts, we here at Reactions call this chemically processed,
calcium injected, black stuff, mana.
So here’s why worm poop is big deal.
Earthworms munch up indigestible garbage and cast out soils that can support healthy ecosystems:
Earthworms break down all that cellulose that could clutter up, then choke out forests.
A herd of earthworms can munch over 20 tons of dead organic matter per acre per year:
all around the world there are examples where they’ve transformed bad grazing land into
bountiful fields.
This is why composters love earthworms -- they’re like earth’s little garbage people.
Thanks little guys!
Of course, it’s worth saying that there are invasive earthworms disrupting ecosystems
in some places.
It’s not all sunshine and ponies in the earthworm world.
The nitrogen returns to the atmosphere, eventually completing the nitrogen cycle, so other plants
can mine that vital element anew and make food for organisms like us.
And all those worms drill little tunnels through the soil to let air and water get deeper to
feed strong roots of plants and trees.
So thank you little garbage people earthworms!
Your poop is really valuable.
Let us know in the comments what creature chemistry you’d like to hear more about.
Slimey hagfish?
Poison dart frogs?
Blue blooded horseshoe crab?
Nature is weird.
Anyway, thanks for watching, and thumbs up on the way out.