Monday, March 26, 2007

Crawling, desperately, to the finish line

In response to the many questions I had about worms from my last post (and especially as a public service to the friends of Michelle who seem to marvel at her insatiable questions of such things), I post here the definitive statements about worms, soggy soil and how they move.

Earthworm - Wikipedia

One often sees earthworms come to the surface in large numbers after a rainstorm. There are four theories for this behavior.

The first is that the waterlogged soil has insufficient oxygen for the worms, therefore, earthworms come to the surface to get the oxygen they need and breathe more easily. However, earthworms can survive underwater for several hours if there is oxygen in it, so this theory is rejected by some.

Secondly, some species (notably Lumbricus terrestris) come to the surface to mate. This behavior is, however, limited to a few species.

Thirdly, the worms may be using the moist conditions on the surface to travel more quickly than they can underground, thus colonizing new areas more quickly. Since the relative humidity is higher during and after rain, they do not become dehydrated. This is a dangerous activity in the daytime, since earthworms die quickly when exposed to direct sunlight with its strong UV content, and are more vulnerable to predators such as birds.

The fourth theory is that as there are many other organisms in the ground as well and they respirate as any animal does; the carbon dioxide produced dissolves into the rainwater; it forms carbonic acid and the soil becomes too acidic for the worms and they come seek neutral nourishment on the surface.

Locomotion and importance to soil

Earthworms travel underground by the means of waves of muscular contractions which alternately shorten and lengthen the body. The shortened part is anchored to the surrounding soil by tiny claw-like bristles (setae) set along its segmented length. (Typically, earthworms have four pairs of setae for each segment but some genera are perichaetine, having a large number of setae on each segment.) The whole burrowing process is aided by the secretion of a slimy lubricating mucus. Worms can make gurgling noises underground when disturbed as a result of the worm moving through its lubricated tunnels as fast as it can. Earthworm activity aerates and mixes the soil, and is constructive to mineralization and nutrient uptake by vegetation. Certain species of earthworm come to the surface and graze on the higher concentrations of organic matter present there, mixing it with the mineral soil. Because a high level of organic matter mixing is associated with soil fertility, an abundance of earthworms is beneficial to the organic gardener. In fact as long ago as 1881 Charles Darwin wrote: It may be doubted whether there are any other animals which have played so important a part in the history of the world, as have these lowly creatures [1]
As a full-service blogger, I’m happy to expand your crawling knowledge. May your running go faster than a worm this week…Persevere.


Backofpack said...

A good and informative report - however, it still leaves many questions unanswered...I think a full scale study is called for. Possibly you should retire and take up the study of worms in your neck of the woods, and I'll retire and study them here. By comparing notes, we should be able to come up with some definitive answers as to what worms think, whether they travel in packs, abandon their young, etc. I'm sure once we publish, we'll be on the talk show circuit for years and probably pulling down the big bucks!

Wes said...

Great post, Joe! LOL. I just accept the fact the hungry birds luv rain :-)

Darrell said...

I can't help but smile at the very idea that you researched and wrote this or that I actually read every word.

And even worse, we still don't really know why the worms are there.

Jenny, Maniac #401 said...

I am officially educated on worms! I love it! Once, I took my daughter to the track to run, she was almost three years old. She ran three whole laps, in her patent leather shoes, and then discovered the worms that had come out and were on the track. She then proceeded to walk the last lap and resue all the worms back into the grass. It was so cute!

WADDLER26.2 said...

I now know more than I ever thought possible about earthworms! You are a full-service blogger and inspire me.