Ref ID : 7102
Taniguchi Akira; [Reproduction and Life Histories of the Tintinnid Ciliates (Review)]. Bulletin of Plankton Society of Japan 25(2):123-134, 1978
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General remarks on the reproductive method of tintinnid ciliate, though almost all knowledges are of the neritic tintinnids, are given. Most common method is the binary fission or plasmotomy, which proceeds asexually. After new peristome with developed membranelles is formed on ventral side of the mother cell and after two daughter cytosomes are almost completely developed, the nuclei undergo visible changes. At late stage of the fission, well-grown two daughters which are connected by a thin and short strand of protoplasm still inhabit a mother lorica. When the daughters are freed, in most cases, since the posterior daughter occupies a mother lorica, the anterior daughter must be provided with a newly built the lorica. Because morphological characteristics of the tintinnid loricae are extremely diversified, the methods of the lorica building should be also very much diversified. It takes, however, only a short period to complete the fission including the lorica building. Among the sexual reproductive methods, isogamous conjugation occurs rather frequently but anisogamous conjugation seems to be very few. Cyst formation has been observed for some neritic tintinnids. From these limited informations, the following life history of the neritic tintinnids could be suggested: Under optimal conditions, the tintinnid populations are rapidly growing at high division rate. As the populations are old, the isogamous conjugation occurs; the growth rate in this period is decreased. The environmental condition become unsuitable, the tintinnids can survive severe season by forming the cyst. Therefore, except a limited period of the cyst stage and for lorica building in some arenaceous species, the tintinnids live free from the sea bottom. Apart from the neritic species, the life history of the oceanic tintinnids, especially that of tropical oceanic species, may be a very simple one among those of marine zooplankters. Role of the loricae in planktonic life of the tintinnids is also discussed.