北海道産アマノリの生活史に關する研究

第I報スサビノリPorphyra yezoensisの研究

抄録

The yield of Porphyra of Hokkaido amounts to 140, 000-150, 000 Yen a year. Although 11 species of this genus have been reported from this district, their life-history has never been studied. Therefore we began it with the study of autumn germs of P. yezoensis, the commonest species of the main island of Hokkaidô, in Usu Bay, Iburi Prov., and obtained the following results.
1) Before September 20th, when setting of propagation provision of Porphyra takes place in Usu Bay, many plantlets which are about 11mm in length, and show the characteristics of “Natu-nori” were observed. From their characteristics they can be identified as P. yezoensis U_EDA.
2) When the water temperature is 20°-17°C they discharge monospores.
The growth of the plantlets does not cease with the formation of the monospores, but they continue to grow, discharging monospores continuously.
3) The monospores are 10-13 μ long, germinate soon after they have been liberated. Up to 5-7 cell stage, they divide only by the transverse walls, forming a thread-like body composed of one row of cells. Thereafter they grow up, tracing the developing process of the so-called “Maruba” type of Dr. K_UNIEDA, to an oval or almost round fronds.
4) The optimum temperature for germination of the monospores is 12°-17°C., and 14°-15°C shows the best effect. From this fact the water-temperature in Usu Bay, after the middle September, seems to be in optimum condition for development of the monospores.
5) Two types of the autumn germ, viz. P. yezoensis typc and P. pseudolinearis type, were observed on the collectors of the propagation ground in Usu Bay. The former (about 10mm in length) also discharges monospores in abundance which trace the process of development just like that of “Maruba” type. The latter, however, forms no monospore. Any specimens of this type could not be found before Sept. 20th.
6) From the results mentioned above, it seems to be. very probable the autumn germs of P. yezoensis are generated hom the monospores, and the young Porphyras thus produced dis-charge monospores again. In such a way the number of germs on the autumn collectors in-crease in geometrical proportion.