The life history and phenology of Colpomenia peregrina (Scytosiphonales, Phaeophyceae) from Japan

Life-history studies on Colpomenia peregrina (Sauvageau) Hamel from Hokkaido, Japan, were carried out in field and culture. In the field, minute gametophytes appeared in late autumn, were fertile from late winter until early summer, and disappeared from mid-summer onward. Sporophytes were found from spring to autumn, bearing ectocarpoid plurilocular sporangia during spring and summer and unilocular sporangia in autumn. Fertile sporophytes were minute and discoid, 1-3 mm in diameter, epilithic or epiphytic, consisting of prostrate and erect filaments, and bearing ascocysts. In culture, zygotes and unfused gametes developed into prostrate sporophytes that were similar in morphology to field-collected sporophytes. These sporophytes produced plurilocular sporangia at 5-20 degrees C, mainly in long-day photoperiods, and unilocular sporangia mainly at 15 and 20 degrees C, both in short days. Spores released from plurilocular sporangia on the sporophytes developed again into sporophytes; however, unispores developed into saccate gametophytes. In cultures from field sporophytes, saccate thalli identical with C. peregrina were obtained. Seasonality of gametophytes of C. peregrina can be explained by photoperiodic and temperature responses in sporangial production of sporophytes.