Paramecia are found in ponds and other quiet waters among the muck and decaying vegetation. A large number of Paramecia in your backyard pond would indicate less than desirable water conditions. This specimen came from my pond in late October, after I had taken the fish indoors, shut down the filter and allowed the decayed vegetation to settle to the bottom for the winter. These two Paramecia came from a sample of the bottom muck.
Paramecia have a weapon defense system that they deploy against their enemies.
When attacked, they release dart-like objects from capsules located on their undersides. It usually works, however, it is completely ineffective against the Paramecium's most deadly enemy - the Didinium. The Didinium simply forges ahead, undeterred, gulping down as many as two Paramecia a minute. Through a complex metabolic process, excess water from the animal's cytoplasm is drawn into the vesicle and expelled as waste matter. A trapdoor at the opening of the vesicle opens and closes to contain the vesicle's contents until the pressure inside forces it open.