Cytoplasmic Streaming and Distribution of Actomyosin Fibrils in the Aphanoplasmodium of Stemonitis herbatica

Summary

The manner of cytoplasmic streaming and distribution of actomyosin fibrils were investigated in the plasmodia of Stemonitis herbatica. Twenty specimens of Stemonitis aphanoplasmodia, one of the three general types of plasmodium, were examined to observe streaming direction and velocity at 15-sec intervals for about 80 min. Many specimens (thirteen out of twenty) displayed both unidirectional and bidirectional flows intermittently intermingled. In some cases (five specimens), only the intermittent bidirectional flow was observed, and in the rest (two specimens), only the intermittent unidirectional flow was seen. All of these three streaming types showed a definite pause during each cycle, whose length ranged between 0.37 and 0.61 of the cycle length. The averaged values of maximum streaming velocities diverged from 21 to 111 μm/sec for twenty specimens. In the coralloid plasmodium, which is produced from aphanoplasmodium at the end of vegetative stage, the direction of cytoplasmic streaming changes alternately without any distinct pause. The averages of maximum velocities ranged from 44 to 83 μm/sec for five specimens.

Well-developed actomyosin fibrils were distributed in tiny anterior portions of the aphanoplasmodium, and also in nodular portions which were formed by gathering of many slender veins in the posterior region. The main veins were diffusely stained with rhodaminephalloidin.