Download 09. Paramecium Species Reading C

The Myth of the Simple Paramecium
Few organisms rank lower in life than the gelatinous, pond-dwelling Paramecium. It consists of
one cell, two orifices, and thousands of hairy feet that project from its surface like beard stubble.
Yet this seemingly primitive organism is capable of some surprisingly complex behaviors. It can
swim 10 times the length of its body in one second, reproduce with and without the help of a
partner, and cunningly hunt for food, all of which allow it to thrive in unsalted waters worldwide.
The myth of the simple Paramecium was shattered in 2006 when scientists sequenced its
genome. They discovered almost 40,000 genes-about twice as many as in a human cell. They
also found evidence of epigenetics, a process by which environmental factors can influence gene
expression without changing the genes themselves. In mice, for example, researchers have
found that a mother's diet can make her offspring more vulnerable to illness later in life.
"Paramecia have the same molecular tools as other organisms," says Purdue University
biochemist James Forney. "Yet their cellular processes are so unusual and eccentric that it forces
you to step back and reconsider what is normal." MARA GRUNBAUM
CENTRAL COMMAND Scientists believe that sometime in the past 10 million years, paramecia
abruptly spliced together two copies of their genome, doubling the number of genes. The boost
in genetic information may have given the Paramecium a survival advantage by allowing for
more beneficial mutations, which drive evolution.
REPRODUCTION Paramecia reproduce asexually, splitting into two identical daughter cells. Yet
they still need sex to survive. Asexual division gradually damages DNA, so periodically paramecia
dock together, exchange small capsules that hold DNA, and within six hours are reinvigorated
with fresh genetic material.
ROWERS Thousands of tiny hairs, or cilia, line a Paramecium's outer edge and work like oars to
propel it through the water. External electric stimulation can force these oars to change
direction. Last year bio-engineers at Stanford University exploited this feature with an arcadestyle game called PAC-mecium that uses electrical pulses to steer live paramecia through a maze
and collect dots.
A HELPING HAND Some paramecia develop mutually beneficial relationships with other
organisms. Paramecium bursaria appears green under a microscope because each cell hosts
hundreds of chlorella algae that supply the Paramecium with sugar and oxygen in exchange for
nitrogen and phosphorus. Austrian ecologists recently found that the algae also protect against
damaging ultraviolet radiation.
© 2011 Discover Magazine