Flagellar Development in the Protozoan Peranema trichophorum,

Changes in flagellar length during the developmental events of flagellar replication and flagellar regeneration were investigated in single cells of the colorless euglenid flagellate Peranema trichophorum at known stages in the life cycle. The leading flagellum could be cut off at any desired length with a tungsten knife operated by a micromanipulator, and the regeneration process recorded photographically. In the regeneration of a flagellum by a postdivision cell, there is a short lag period followed by an elongation with a deceleratory rate. The relationship between elongation rate and flagellar length holds true regardless of the initial stump length. The elongation rates at given lengths are greater in predivision cells than in postdivision cells. At cell division, the parental leading flagellum rapidly shortens at a constant rate and disappears, while simultaneously two new leading flagella elongate at a deceleratory rate. Elongation continues at slower rates throughout interphase. The elongation kinetics of the flagellum during the normal cell cycle, and the kinetics of regeneration at different cell ages have been satisfactorily accounted for by a mathematical model. Shortening and elongation were compared and the relationship between them was discussed in light of the finding that shortening interrupted regeneration in some predivision cells. It was concluded that at least part of the control exerted over flagellar length changes resides in the flagellum itself. The lag period remained the same under a variety of experimental conditions, suggesting that it is a “wound healing response”.