Distribution of Tetrahymena pyriformis in Europe *

Abstract

One hundred eighty-eight fresh-water samples from France (30), Italy (42), Austria (12), Germany (1), Switzerland (35), Holland (20), England (26), and Sweden (22) were examined for T. pyriformis. The habitats included rivers, mountain streams, lakes, ponds, irrigation ditches, roadside ditches, running and dead water canals, and fountains. The temperature ranged from 10° to 30°C, locations from 42° to 68° North latitude, with elevations from sea level to approximately 3,000 feet. Of the samples taken 28 contained T. pyriformis from which 411 clones were established in axenic media. Thirty-three additional samples contained ciliates other than T. pyriformis. All clones grew well in 1% proteose peptone; when screened for their nutritional requirements a few failed to grow on the completely defined medium and several others survived eight sub-inoculations without thiamine. The nuclear and sexual activity pattern followed that of previous collections. In distribution, variety 6 was found in Italy, variety 3 in Austria, and variety 4 in England. A new variety (variety 10) with two mating types was isolated from four different habitats in England. Several strains from Italy, France, Holland, and England constitute one group which mated among themselves, but only a few of which reacted with mating type I of variety 6 from America. This demonstrates the close affinities of the European and American strains, yet shows the possible evolution of a new variety (species).