ヒジキの卵・精子の放出及び幼胚の離脱と着生について (海藻の胞子付けの研究第11報)

概要

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Hijikia fusiforme is an edible fucaceous alga, growing in tidal zone in Japan. It sheds eggs periodically at the intervals of seven to eight days (cf. Table 1), from the end of May (water temp. 19°-20°) to early July at Misaki, Kanagawa Prefecture. Shedding occurs in a flood tide of day-time. About 105 eggs are shed from a female plant in a season. As was reported (Tahara, 1929), each egg is enclosed in a gelatinous coat, the latter of which is attached to the mother plant by a stalk. Under this condition the egg is fertilized and develops to an embryo. In the authors observation, about 24 hours after the shedding, the coat dissolves and the embryo is liberated into the sea water (cf. Fig. 1 and Table 2). In laboratory experiment, when the sea water containing the liberated embryos is taken on a glass plate, and the water is carefully run off, so as to assure a contact between the embryos and the plate, many embryos are found fixed in one minute. If the embryos are left with an ample sea water, most of them remain unfixed after five minutes (cf. Table 3). The fixing ability is the strongest just after the liberation. Therefore it is right to suppose that, in nature, the embryos will fix themselves to rock surfaces on the following day of the shedding, and they may accomplish it within one minute, especially on the rocks which are washed by waves at flood tide.