A CULTURE STUDY OF CAULACANTHUS-USTULATUS (CAULACANTHACEAE, GIGARTINALES, RHODOPHYTA) FROM EUROPE AND ASIA

Caulacanthus ustulatus (Turner) Kutzing was collected near Roscoff on the north coast of western Brittany and isolated into unialgal culture . The species is a recent introduction in this area, and the nearest k nown locality before 1986 was Biarritz. Two other Caulacanthus isolate s were studied in culture and compared with the Roscoff isolate. One c ame from Gibraltar, not far from the type locality (Cadiz), and the ot her was from Qingdao, China, where the alga is passing under the name C. okamurae Yamada. The three isolates were morphologically similar, a nd thus supporting the recent proposal of reducing C. okamurae to syno nymy with C. ustulatus. The isolate from China remained vegetative in culture, while the European isolates produced tetrasporangia. Germinat ion of tetraspores and mature male and female plants are described for the Roscoff isolate. Only one carposporophyte was produced, and the g ermination of carpospores is described. Vegetative growth was measured on a temperature gradient growth table. Very little growth took place at 6 degrees C. Growth was best at ca. 17 degrees C, and slightly red uced at 13 degrees C and 26 degrees C.