Earthworms & Their Natural Protection
Gardeners love earthworms. Worms aerate the soil and by eating and excreting their own body weight every 24 hours, provide plenty of natural fertilizer as well. Still, the soil can be a dangerous place for an earthworm. Worms are likely to face numerous threats to their lives, stemming from fishermen, birds, reptiles, moles and the weather. Earthworms owe their continuing survival to the many protections they have adapted in response to these threats. Does this Spark an idea?
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Color
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An obvious protective adaptation of the earthworm is its earth-like color. Worms actually vary in the tone of their coloring, but they are all pretty much the color of earth. This provides camouflage from surface predators such as birds.
Mucus
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The mucus covering of an earthworm protects it from getting dried out too easily, but will not protect the worm for long from an environment that is too dry. Worms' skin must remain moist to allow them to absorb oxygen, since they lack lungs. Too much moisture is not good either. While some species can survive being submerged for up to two weeks, most will flee to the surface when the soil is flooded. Unfortunately for the worm, the surface is a terribly unsafe place and those worms not eaten or collected by fishermen may well get stranded and dry out when the sun returns.
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Bristles
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If you have ever tried to pull an earthworm out of the soil but have felt how it resists, clinging to the earth, you have experienced the power of "setae." Setae are small bristly hairs that cover an earthworm's skin which it uses for locomotion and to cling to the soil. The setae can anchor the worm so firmly in the soil that it can break before being completely extracted.
Healing Ability
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Being broken is not such a big problem for earthworms. Earthworms, when cut in half, do not grow into two separate earthworms, contrary to popular myth. However, if the worm is severed far enough back, the earthworm will grow a completely new back end. The old back end, however, will die if left alone, but more likely it will be consumed by a scavenger or predator.
Senses
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Earthworms lack many of the sensory organs common to more complex animals. They have no eyes or ears, but their mouths are highly sensitive to vibration and their skin cells are sensitive to light. An earthworm's sensitivity to vibration is so acute it can feel a robin poking around in the ground above it. Sometimes, however, the earthworm reacts to vibrations in a way detrimental to its survival. Earthworm collectors have long known of a technique called "worm grunting" which involves creating vibrations in the ground which draw earthworms to the surface where they are easy to collect. No one is quite sure why earthworms react in this way, though Charles Darwin and others have theorized that worms surface in an attempt to escape moles who might be reluctant to follow them.
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References
- Photo Credit worm image by Ksenija Djurica from Fotolia.com
