抄録
The present paper deals with growth and attachment of isolated utricles from various parts of thalli in Codium fragile (Suringar) Hariot, with utricles from different stages being studied in laboratory culture in order to select suitable utricles for conducting assays on seaweed attachment. Clavate utricles were observed in the thalli at three stages: utricles without a gametangium, those with a gametangium before and after gamete release, and slender utricles without a gametangium. The clavate utricles were abundant except for the basal parts of the thalli, so that these utricles were used in the present study. The utricles isolated from six parts of the thalli and those at three different stages had the ability to form medullary filaments and attach to the substratum by their elongated filaments. However, the ability of the isolated utricles to elongate their filaments differed among the parts of the thalli used for isolating the utricles, and the ability of the utricles to form and elongate their filaments differed among the stages of the utricles. Furthermore, utricles with a gametangium were obtained only in a certain period when the thalli were fertile. Therefore, the clavate utricles without a gametangium isolated from the higher orders of axes are more suitable for use in assays on seaweed attachment.
