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-s tep cooling method was attempted. A solution composed of 10% DMSO and 0.5 M sorbitol in 50% seawater had the most favorable cryoprotective e ffect on the conchocelis. The appropriate cryopreservation procedure w as as follows: DMSO was added gradually over a period of 15 min follow ed by an equilibration period of several minutes. Conchocelis cells we re then prefrozen to -40 degrees C at O.1-1 degrees C/min prior to imm ersion in LN. After storage in LN, the conchocelis suspension was thaw ed quickly by agitation of the vial in a water bath at 40 degrees C, a nd 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, a nd retained the ability to form conchospores which grew into gametophy tic thalli.