Effect of Salt Concentration on Regeneration Rate in Blepharisma Acclimated to High Salt Levels

SYNOPSIS. Individuals of Blepharisma intermedium (Rao A race) acclimated by prolonged growth in axenic medium containing 8X, 16X, 24X and 32X the concentration of salts in unit standard balanced salt solution (USBSS) used for fresh‐water protozoans were tested for rate of regeneration at various salt concentrations, the time for 50% regeneration being used for comparisons. Blepharismas acclimated to axenic medium (of osmolality 10 × USBSS) containing 16X USBSS regenerated at about the same rate as those grown in axenic medium but were delayed at higher salt concentrations. The same was true for those grown in axenic medium containing 32X USBSS, except that the range of higher salt concentration tolerated was much greater. Those acclimated to higher salt concentrations were delayed in regeneration by exposure to lower salt concentrations tolerated by controls. Because growth was very slow in media of higher osmolal concentration, it was not possible to determine the internal concentration of salts in acclimated cells. The morphogenetic process as measured by rate of regeneration, appeared to be less sensitive to increased salt concentration than growth, as measured by cell division.