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The Learning Kingdom's Cool Fact of the Day for September 8, 1999
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What creatures have four kinds of legs?
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Decapod crustaceans (shrimps, crayfish, and lobsters) have 14 pairs of
"legs", divided into four different groups.
The first three pairs, just behind the animal's mouthparts, are
"eating legs" (maxillipeds), used to manipulate food before passing
it forward to the mouthparts. They are usually hidden beneath the
head/thorax shield (carapace).
Next are five pairs of "walking legs" (pereopods). In some
crustaceans, the first pereopod is equipped with a large claw. Some
pereopods have gills attached near their bases.
Behind these are five pairs of "swimming legs" (pleopods), used for
swimming slowly forward. Some crustaceans carry their eggs among
their pleopods.
Finally, there is one pair of "tail legs" (uropods) that are part of
the tail fan, which is used for sudden backwards flight from
predators and other potential threats.
Diagram of decapod anatomy:
http://www.mbl.edu/html/KEYS/INVERTS/13/decapod.general.gif
More about shrimp biology:
http://www.mov.vic.gov.au/crust/caribiol.html
More Cool Facts about crustaceans:
http://www.cool-fact.com/archive/1999/03/24.html
http://www.cool-fact.com/archive/1999/04/21.html
http://www.cool-fact.com/archive/1997/02/18.html
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Cool Fact Correction for August 31st
In the Cool Fact for August 31st, we reported that the largest
man-made explosion took place at Bikini Atoll in 1954. However, there
was a larger explosion that occurred in the former USSR with a
50-megaton surface detonation in 1961.
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