Artificial induction of autogamy inParamecium caudatum

Abstract

SUMMARYThree methods of artificial induction of autogamy in Paramecium caudatum were described: (1) treatment with KCl+papain, (2) treatment with KCl and then with KCl + papain and (3) ordinary mating reaction and then treatment with papain. As expected, one-to-one segregation ratios were obtained in the progeny from the parents heterozygous for the two loci: mating type and lactate dehydrogenase. A high rate of autogamy is induced by method (1), but its use is restricted to only a few clones. Autogamy is also induced at a high rate by method (2), by which the induction is more stable. Autogamy is induced at a lower rate by method (3), but this method can be widely applied to every species of Paramecium which has complementary mating types. Some exautogamous progeny become completely sterile through successive autogamy. The cause of this sterility is discussed.

Interspecific conjugation between distantly related species of Paramecium.

“…Although more than a thousand cells were observed, nuclear activation did not occur. It is known that when protease is added to the conjugation-inducing chemicals at various times from the start of the induction of conjugation, conjugants once united are gradually disjoined, and the separated cells undergo autogamy in P, caudatum (Tsukii and Hiwatashi 1979). Similar experiments were performed in P. bursaria as the second attempt of induction of autogamy.…”

“…Autogamy occurs naturally in P. tetraurelia or can be induced artificially in P, multimicronucleatum and P. caudatum (Miyake 1968;Tsukii and Hiwatashi 1979;Mikami and Koizumi 1979). Thus, cell union is not indispensable for nuclear activation in the `aurelia' group.…”

“…hrd is a mutant whose mating reaction lasts long and natural autogamy does not occur (Sonneborn 1974). 27aG3 (Tsukii and Hiwatashi 1979) is an exautogamous clone, derived from an early mature mutant (Myohara and Hiwatashi 1979). T151 is a mutant in which conjugation can be induced chemically (Endoh, unpublished).…”

Local Degeneration of Cilia and Nuclear Activation during Sexual Reproduction in Paramecium caudatum

“…It has been proposed that the duration of cell union is essential for nuclear activation in ordinary conjugation (5, 6 , 7, 8, 9). However, the facts that natural autogamy occurs in P. aurelia and that autogamy can be induced artificially in P. caudatum and P. multimicronucleatum indicate that cell union is not indispensable for nuclear activation (8,10,11). Although there is no cell contact in chemically induced autogamy, degeneration of cilia occurs in the autogamous cell (3,4,10).…”

My Paramecium Study, Retrospect and Prospect

“…The lack of autogamy was overcome by artificial induction of autogamy by interrupting conjugation by proteases (Tsukii & Hiwatashi, 1979). To make the long immature period shorter or nothing, I first tried to culture immature cells in the medium containing brei of mature cells.…”