GROWTH STUDIES ON CILIATES

VI. DIAGNOSIS, STERILIZATION AND GROWTH CHARACTERISTICS OF PERISPIRA OVUM

¹ Arnold Biological Laboratory, Brown University and the Marine Biological Laboratory, Woods Hole, Mass.

1. Perispira ovum is a member of the family Spathidiidae. It is carnivorous, feeding on euglenoid flagellates.

2. A morphological description is given in order to establish the identity of the experimental organism.

3. A description of the mechanism of feeding is given. Perispira possesses a spiral ridge to which the flagella of euglenoid flagellates adhere. The flagellum and then the body of the prey is drawn into the mouth of the ciliate where it eventually rounds up and is digested. The cytoplasm of the prey is digested first, then the chloroplasts and lastly the paramylum bodies.

4. Perispira was rendered bacteria-free and established in culture with sterile Euglena gracilis as food.

5. When the population of such a culture is followed, a typical growth curve results. If ciliates from an old culture are used as the inoculum there follows a period of lag, a logarithmic growth phase, a phase of negative growth acceleration, a stationary phase and a phase of slow decline.

6. Cell size increases during the lag phase and early logarithmic phase but decreases rapidly during the late logarithmic phase and phase of negative growth acceleration. Cell size is correlated with the presence of food and the rate of cell division.