Tetrahymena

Tetrahymena, a unicellular eukaryote, is a genus of free-living ciliates. The genus Tetrahymena is the most widely studied member of its phylum. It can produce, store and react with different types of hormones. Tetrahymena cells can recognize both related and hostile cells. They can also switch from commensalistic to pathogenic modes of survival. They are common in freshwater lakes, ponds, and streams. Tetrahymena species used as model organisms in biomedical research are T. thermophila and T. pyriformis. The most recent common ancestor to this genus was probably a small flagellated cell.