Fig. 4. A typical type-IV cell (A-K) and two type-IV cells of similar size sharing an common apical opening (L-O) at 72 h of the freshwater-to-seawater transfer experiment. (A,C,E,G,L) X-Z optical sections. (B,D,F,H,I,J,K,M,N,O) X-Y optical sections. n, nucleus; ac, accessory cell; ^*, apical opening of type-IV cell. Scale bar, 10 µm.