|MadSci Network: Zoology|
Dear Ms. Starr, As with most answers to science questions, the real answer is 'it depends.' My first thought is, why do you want to cut an earthworm in four pieces? Why not two, or five? Depending on how you cut the earthworm, part of it will either survive (not all four pieces will) or the whole thing will die. Earthworms are annelids, or segmented worms. Nightcrawlers, the big wiggly worms often used as fishing bait, have about 150 segments, while manure and red worms (red worms are also fairly common) have 95 segments. Different segments perform different functions, just like our body parts. We don't expect an arm to do what a toe can do, and the same thing is true for the segments of a worm's body. Here's a great site with tons of worm info, and lots of drawings of earthworm anatomy: http://members.aol.com/camusurca/earthworms/eartworm.htm Regarding your real question: Earthworms run into this problem all the time, since birds like to eat worms. When a bird tries to yank a worm out of its burrow, the worm uses bristles on its skin to hang tight to the wall of the burrow. If the bird pulls hard enough, it can yank off part of the worm's body. If the worm is broken off at the first seven or eight rings, it can grow new segments and will survive. If the worm is pulled in half, only the head end grows back. So, if you cut a worm into four pieces, you most likely won't get four happy worms. If you cut a worm into two pieces, you may get two worms, if you don't cut too far down the worm (only 7 or 8 segments down). If you cut the worm in half, you'll get one live worm after the head end grows back, but the stress of being chopped in two may kill both ends. I'm guessing that being split in half is hard on the poor thing. This information came from the following worm site, which has all kinds of details about earthworm anatomy and natural history: http://www.nysite.com/nature/fauna/earthworm.htm If you really want to experiment with regeneration, I suggest working with planaria, which are a kind of flatworm. They're generally very small, so it's harder to see everything happening (a magnifying glass helps), but they can regrow after many divisions. I remember a junior high experiment in which we cut a planarian in three pieces, and the head and tail parts grew back quickly and were healthy, but the middle section was always sluggish, even though it regrew a head after a few days. A side note, just because this is my favorite worm story: Charles Darwin was a big fan of earthworms, and spent a lot of time and energy studying their behavior. He wanted to know if earthworms can hear, so he set up a box of earthworms and played various musical instruments at them to see if their behavior would change in response to a tin whistle, an oboe, or a bassoon. His hypothesis was that if they heard in a high frequency, they might move in response to the tin whistle but not the bassoon, or vice versa. I read about this experiment in a book by David Quammen, and would like to know more about this work because it makes me smile. Can you imaging playing drums for a box of worms? I hope this helps answer your worm question, and encourages you to learn more. best regards, Ruth
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