CRYOPRESERVATION OF THE CONCHOCELIS OF THE MARINE ALGA PORPHYRA-YEZOENSIS UEDA (RHODOPHYTA) IN LIQUID-NITROGEN

Cryopreservation of the conchocelis of Porphyra yezoensis by the two-step cooling method was attempted. A solution composed of 10% DMSO and 0.5 M sorbitol in 50% seawater had the most favorable cryoprotective effect on the conchocelis. The appropriate cryopreservation procedure was as follows: DMSO was added gradually over a period of 15 min followed by an equilibration period of several minutes. Conchocelis cells were then prefrozen to -40 degrees C at O.1-1 degrees C/min prior to immersion in LN. After storage in LN, the conchocelis suspension was thawed quickly by agitation of the vial in a water bath at 40 degrees C, and cryoprotectants were washed off by gradual dilution with seawater. The survival was independent of the period of storage at least for 300 days. The survival evaluated by staining with neutral red was approx. 60%. The conchocelis cells stored in LN were able to form colonies, and retained the ability to form conchospores which grew into gametophytic thalli.