抄録
Starfish (Asterias amurensis) made a sudden attack in large number on the coast of Tokyo Bay from October 1953 to March 1954 and devoured large quantities of clams (Meretrix, Venerupis, Mactra etc.)
The experiment was desiged to find out the optimum temperature for the larvae (Bipinnaria) and the young of the starfish and the optimum specific gravity for the larvae. The larvae used in the experiment were obtained by artificial fertilization and reared in Tauchi's thermostat for 22 days from March to April 1954. Similary, the young of the starfishes (arm length 4-9mm), collected from sea bottom by dredge were reared in the same thermostat for 30 days form April to May. The larvae used in the exeriment dealing with the optimum specific gravity were reared in Petri dishes for 22 days from March to April. The results obtained were as follows:
1) The optimum temperature for Bipinnaria and young starfish is 5-20°C and 5-26°C respectivly (see Table 1 & 2).
2) The optimum specific gravity for the Bipinnaria is 1.011-1.026 (δ15) (see Table 3 & 4).
During the seaon of high summer temperature, both young and adult starfish died in great numbers. This fact seems to prove that the range of temperature tolerance for both adult and young is similar. The upper limit of tolerance in the young starfish was found experimentally to be 26°C. It seems probable that the appearance of starfish in vast number in Tokyo Bay during the peried from October 1953 to March 1954, was related to the unusually low temperatures which prevailed during the summer of 1953, which in turn, permitted the survival of the unusually large number of individuals.
