Naegleria is a common soil amoeba – the sequenced organism was isolated from the mud in a grove of eucalyptus trees on the UC Berkeley campus – that, under stress, quickly grows two flagella, like sperm tails, that it uses to swim around. It has a third identity, a hard cyst, that can persist in the soil until conditions become damp and warm enough for it to turn into an amoeba.
http://www.eurekalert.org/pub_releases/2010-03/uoc--gsc030310.php