Mating Types in Stylonychia putrina.

Abstract

Although conjugation in ciliated Protozoa was long extensively studied, especially by Maupas(1), mating types were first discovered by Sonneborn(2). It is now known that mating types exist in Paramecium aurelia(2,3) P. bursaria(4-6), P. caudatum(7-11), P. multimicronucleatum(11), P. trichium(12), P. calkinsi(12-14), and Euplotes patella(15). In several of these species, a number of varieties have been recognized, each with its distinctive mating types; and the number of interbreeding mating types within a variety is 2 in some cases, 4, 6, or 8 in others. The present paper reports 5 mating types in Stylonychia putrina Stokes, like Euplotes a hypotrichous Ciliate.

Material and methods. The clones of Stylonychia putrina used in the experiments reported here were collected at Lake Arrowhead in Southern California on August 30, 1949; September 25, 1949; June 27, 1950; and September 24, 1950. In all, 41 clones were isolated and established. The culture medium and methods were essentially those described by Sonneborn and Dippell(16).

Mating conditions and behavior. In testing for mating type, the clones were mixed during the first half of the forenoon. Pairing occurred only if the animals were numerous in the mixtures. The tendency to form pairs appeared to be stronger immediately succeeding food exhaustion. For this reason it was found advisable to add a drop of culture medium to each mixture, as made, as Kimball(15) did with Euplotes patella. If the animals were numerous, this amount of food was soon used up and pairing followed. When different mating types were mixed there was no immediate agglutinative reaction such as is found in Paramecium, but sometime later the animals gathered closely together in the bottom of the depression slide. Their normal jerking movements were accelerated; they appeared to be greatly excited.