1994 Fiscal Year Final Research Report Summary
Studies on the life history of marine algae.
| Project/Area Number |
05640786
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
系統・分類
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| Research Institution | Tokyo University of Fisheries |
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Principal Investigator |
OHBA Hideo Tokyo University of Fisheries, Department of Aquatic Biosciences, Assistant Professor, 水産学部, 助手 (40185369)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Marine algae / Chlorophyta / Caulerpales / Codium / Culture / Life history / Multinucleate / Fluorescent microscopy |
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| Research Abstract |
Four taxa of coenocytic marine green algae belonging to Caulerpales, Caulerpa racemosa var.clavifera f.macrophysa, Caulerpa microphysa, Codium fragile and Codium divaricatum, were established the unialgal culture and were observed their reproduction, development and the behavior of the nucleus.
Both species Caulerpa had the same haplobiontic life history as those of C.racemosa var.laetevirens (Enomoto & Ohba 1987) and C.racemosa var.peltata (Ohba et al.1992). The protoplasm of fertile Caulerpa aggregated and formed an irregular network. Anisogamous biflagellate male and female gametes were produced in the protoplasmic network and copulated with each other. The plant was monoecious and holocarpic. Settled zygotes became protospheres and increased in volume. After on month, they formed two germ tubes bipolarly. Germlings developed into filamentous protonemata after on month. Protonemata formed thick primary shoots which differentiated into creeping rhizomes and upright shoots. They develo
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ped into the plant similar to the shape of the mother one after four months. These secondary generations repeated the same life history as that of the mother plant. It is uncommon for marine green algae that zygotes develop into protospheres and increase in volume as it is spherical but they do not form germ tubes for more than one month, except for Halimeda and Udotea (Meinesz 1980).
The life history of two Codium species were almost the same as those repotred (Arasaki et al.1956, Borden & Stein 1969).When Codium matured, lanceolate male and female gametangia were produced on the utricles. The plant was dioecious and eucarpic. Anisogamous gametes copulated with each other. Zygotes formed two germ tubes bipolarly just after settling. After two months, germlings developed into tufty plants composed of branched filaments with plugs. Although germlings were cultured in various conditions for six months, they did not form utricles and develop into the plant similar to the shape of the mother one.
On the observation of the behavior of nuclei in four taxa, it was recognized that when zygotes or protospheres form the germ tube, their nuclei are multinucleated. I am going to make more clear the Codium-type life history with re-examination of the chromosome number and the position of meiosis in the life history. Less
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