The Lowly Worm
For a lowly, inconspicuous creature, seldom seen, never heard and only occasionally smelled, the earthworm has an importance for us humans which belies its unimpressive appearance. It is often one of the first creatures of nature which children notice and investigate. Who does not have early memories of walking to school after a heavy rain, either trying to avoid them, or (among the more nasty of us) purposely squishing them and releasing that pungent, worm odor so associated in our minds with wet earth and rain?
Worm usually have the honour of being the first animals dissected by school children. Alive and squirming, they are a favorite bait to adorn the end of a fisherman’s hook since fish love them, as do a lot of other creatures the robin being the most famous. Woodcock, a favorite game bird, lives mostly on worms. They also make up a large part of the diet of snakes. In fact, any animal which fancies worms can pretty well help itself for the worm’s one and only defence is to disappear into the earth and stay there. Some species of earthworms never come to the surface at all.
Worms are nutritious enough to make them worthwhile food for even us humans, being about 60% protein when dried. However, the strong gamey flavour, together with our own ingrained squeamishness makes them an unlikely addition to our pantry.
But it is as caters themselves that worms are of the greatest value to us. Their entire purpose in life is to cut and devour just about anything which they come across whole burrowing through the soil. In the process, they pick up bits of plants and animal material which they process into their own food requirements. Charles Darwin called the earthworm “nature’s plowman” and estimated that earthworms alone can turn over two tons of soil a year in one hectare of land. Every ten years or so the earthworm replaces the top 3 centimeters of soil. Worms move through the earth by wiggling through gaps and crevices in their search for the best morsels. If the soil’s too compacted, they simply cut their way through, thereby aerating and loosening the soil as they go. But they always deposit their wastes in casing at the mouth of their burrow on top. This continual removal from the bottom and depositing on top has leveling effect on the soil, as well as a lowering effect for anything built on top. Stonehenge, that famous British relic from the distant past, is slowing sinking because of the activities of these voracious creatures.
Since worms spend so much time underground, they have little use for eyes. All they have in this regard are light sensitive cells in their “heads”. Worms avoid light, coming above ground only at night. They especially dislike blue light while they are more tolerant of red light. Since its underground burrow is the worm’s only defense from predators, it does not go far from it when it surfaces. The worm keeps its posterior end attached to the entrance so that if frightened, it can withdraw to safety by a quick contraction of its body.
Worm tunnels can go as deep as six feet. If the weather is too hot or too cold or too dry, (worms breathe through their skin and must keep it moist) they simply stay deep in the soil. The worms you see in the soil this autumn will not die off over winter, but will burrow beneath the frost line and stay inactive until spring.
How many times have you sliced through a worm while digging in the garden and watched it wiggle away? Can worms really survive such a grievous injury? Actually worms do have an ability that would be very handy for us humans to have: They can grow back missing body parts if the part isn't too big a portion of the total. Worms are built in segments called somites. From the “head” end, the worm can lose 8 to 9 segments and grow them back again. From the tail end, more can be lost. This has given rise to some bizarre experiments. Worms have been shortened by removing segments or lengthened by grafting together 2 or 3 worms to make a very long one. Even two tail ends have been joined together, although the text book which described this didn’t reveal how long this particular worm survived.
Worms have another attribute that makes their lives somewhat less complicated than ours: they are all hermaphrodites, meaning they are both male and female. When two worms meet and are in the mating mood, they simply exchange sperm before moving on. A worm cannot however, fertilize him/her self but needs another worm to do it, not a big problem considering the abundance of worms.
Elaine Farragher, August 22, 1988
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