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.
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.
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 bioengineers at Stanford University exploited this feature with an arcade-style 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.