Laboratory culture and taxonomy of two species ofDerbesia (Class Chlorophyceae) in Japan

Two species ofDerbesia (Class Chlorophyceae),D. marina andD. tenuissima, have been studied for the purpose of obtaining a better understanding of their morphological details and life histories, using preserved and living specimens as well as laboratory cultures. The life histories of both species were completed in the laboratory, starting from both zoospores and zygotes. Specimens were collected at Asamushi, Aomori-ken, and Shimoda, Shizuoka-ken. Their life history types are fundamentally identical, zoospores giving rise upon germination toa Halicystis-phase, while zygotes grow into aDerbesia-phase. The thallus of theHalicystis-phase which alternates withD. marina is the same as that ofH. ovalis which grows in the northern regions of Japan. On the other hand, the thallus of theHalicystis-phase alternating withD. tenuissima is the same as that ofH. parvula known to occur in the temperate to subtropical regions of Japan. These results coincide with those obtained withD. marina andD. tenuissima in Europe, where the type localities of both species are located. Specimens assignable to these two species were collected at several localities in Japan and, as a result of detailed examination of the morphology, they are believed to be identical with eitherD. marina orD. tenuissima.