海産ゾウリムシ(Paramecium calkinsi)の接合時における小核の行動
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概要
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1) When animals of different mating types of Paramecium calkinsi are mixed under the appropriate condition, and first, a few paramecia are seen to stick together (mating reaction); and then these clumps form a larger one (twenty minutes later). Then this immense clump breaks up into smaller ones, finally only the pairs of conjugants are formed (approximately three hours later). The conjugants usually separate one another during the third postzygotic division (ten or eleven hours later). 2) One or two of the two (or one) micronuclei undergo the first prezygotic division which is characterized by the formation of prophase crescent. These two or four products undergo the following second prezygotic division. This first two divisions are those of maturation and the second prezygotic division seems to be reductive. Only one of the four or eight products completes the third prezygotic division in the paroral cone to form a male (migratory) pronucleus and a female (stationary) one. The fusion nucleus (synkaryon) in each conjugant is formed by the exchange of gametic nuclei through the paroral cone. The first postzygotic division of synkaryon result in the formation of non-viable nucleus and viable one which completes the second and the third postzygotic division. Two of these products develop into the macronuclear anlagen and the other two (occasionally one) become the micronuclei. 3) About four or five hours after the animals have entered into the conjugating process, degeneration of the macronucleus in each conjugant begins. It stretches out to be a long skein (ten or eleven hours later), then breaks into small round fragments. During successive fissions of the exconjugants the fragments are destributed, without multiplying, to the daughter cells and are ultimately resorbed by the cytoplasm. 4) After third postzygotic division, two products at each end of the body begin to migrate toward the center of the body (oral region). Among these four products, two (rarely three) which migrated earlier than the others seems to become the macronuclear anlagen.
- 社団法人日本動物学会の論文
- 1956-08-15
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