ムラサキイガイの生殖腺の周年変化と性現象について
1959 年 25 巻 1 号 p. 1-6
詳細
1959 年 25 巻 1 号 p. 1-6
The rate of occurrence of sexually mature individuals of Mytilus edulis was the lowest in August and rose to almost 100% when the water temperature came down to about 18°C. (October-November).
Seasonal change in maturity based on Chipperfield's classification of stages was as follows:
July-August: Stage 0, August-September: Stage I, September-November: Stage II, November-April: Stage III, May-July: Recently spent Stage.
The minimum size of the mussels sexually mature was found to be 23-24mm in shell length. In one exceptional individual measuring only 10mm. in shell length, the spermatozoa were motile in sea water.
Maturation process of young mussels was comparatively slow.
Sex ratio varied in accordance with age. As a rule, among fully grown individuals, more females were encounted than males, although among extremely large individuals, the sex ratio again approached 1:1.
Ten hermaphrodite mussels were found and these were interpreted as cases of accidental hermaphroditism.
