Abstract: Bryopsis hypnoides Lamouroux was regenerated in vitro from the protoplasm squeezed out from wild algae and the regenerated individuals had an advantage over individuals from the wild in terms of growth. Culturing of segments of thalli also showed that segments from the regenerated algae grew better than those from individuals from the wild. The segment that corresponds to a part of a cell, at least a part of the protoplasm, can develop into a mature individual, including rhizoid and thallus, suggesting that a multinucleate alga, such as B. hypnoides, is different from higher plants, whose totipotency is based on an intact cell (or protoplasm). Further cultivation of mature individuals from segments indicated that the organelles in the thallus had two ways in which they could survive when the alga was on the decline: (i) the organelles were transferred into a ball with a gelatinous envelope through a formed pipe and the ball seemed to be capable of being propagated; and (ii) the organelles were aggregated in the thallus and then moved to the outside. An interesting result is that one organelle aggregation located outside the thallus germinated and developed into a mature alga, although most organelle aggregations gradually lost vitality and died. The results of the present study reveal that the aggregation of organelles can regenerate a stronger organism than individuals from the wild owing to the complete exchange of genetic material and may possibly enable organelles to survive in unfavorable surroundings.(Author for correspondence.Tel: 0532 8289 8574; Fax: 0532 8288 0645; E-mail: gcwang@ms.qdio.ac.cn)

Key words: aggregation, Bryopsis hypnoides, culturing thallus segment, development, germination, protoplast.