In the polymorphic ciliate Tetrahymena vorax, the non-selective phagocytosis seen in microstomes changes to a highly selective process in macrostomes
Heidi K. Grønlien*,
Trond Berg and
Arne M. Løvlie
Department of Biology, University of Oslo, PO Box 1051 Blindern,
N-0316 Oslo, Norway
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Fig. 1. The distribution of latex beads in the pouch of macrostomes. Macrostomes
were allowed to prey on latex beads with a diameter of (A) 20.3 µm and (B)
30.0 µm. The macrostomes did not differentiate between these two sizes. The
macrostomes did not capture latex beads with a diameter of 3.0 and 41.3 µm.
In all experiments, the concentration of beads was 106
ml-1. The experiment was repeated three times, and 50 cells are
counted in each experiment. Values are expressed as the mean + S.E.M.
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Fig. 2. The percentage of macrostome cells that captured either deciliated
Tetrahymena thermophila (grey columns) or latex beads with a diameter
of 30 µm (stippled columns) in a medium containing (A) only deciliated
T. thermophila, (B) only latex beads and (C) both deciliated T.
thermophila and latex beads. The macrostomes consistently selected the
cells rather than the beads. In all experiments, the concentration of the prey
was 106 ml-1. The experiment was repeated three times,
and 100 cells were counted in each experiment. Values are expressed as the
mean + S.E.M.
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Fig. 3. (A) A macrostomal Tetrahymena vorax that has captured a latex bead
with a diameter of 30 µm. The picture was taken 30 min after capture of the
bead; there was no sign of phagocytosis of the latex bead. Scale bar, 20
µm. (B) A macrostomal cell Tetrahymena vorax that has phagocytosed
a latex bead together with a T. thermophila cell. The picture was
taken 10 min after adding T. thermophila cells and latex beads to the
medium. Scale bar, 20 µm.
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Fig. 4. Diagram of the behavioural response of a macrostomal cell of
Tetrahymena vorax after capturing a T. thermophila cell. The
macrostome selects a T. thermophila (1) and captures it (2). The
macrostome continues to swim in the same direction for 1.7±0.6 s (mean
± S.E.M., N=8) (3) before briefly swimming backwards and the
anterior part starts to contract (4); this is followed by cell rotation (5).
The total duration of the chain of events depicted (1-5) was 28.3±5.2 s
(mean ± S.E.M., N=8). The cell then swims forward again, the
prey is in a digestive vacuole (DV) (6). It normally takes 10-13 min before
phagocytosis restarts.
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Fig. 5. The effect of cytochalasin B (10 µg ml-1) on phagocytosis in
a macrostomal cell of Tetrahymena vorax. Both pictures are taken 30
min after the addition of T. thermophila to the medium. In the
control cell (A), phagocytosis of three T. thermophila cells has
occurred. In the cytochalasin-B-treated cell (B), the T. thermophila
has been captured but no phagocytosis has taken place. DVs, digestive
vacuoles. Scale bar, 20 µm.
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Fig. 6. The distribution of digestive vacuoles (A) in untreated microstomes
(control) and (B) in cells treated with 5 µmol l-1 nocodazole.
No significant differences were observed between the control and treated
cells. In all experiments, the concentration of T. thermophila was
105 cells ml-1. The experiment was repeated three times,
and 100 microstomal cells were counted in each experiment. Values are
expressed as the mean + S.E.M.
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Fig. 7. The distribution of digestive vacuoles in macrostomes in untreated
microstomes (A) (control) and in cells treated with 0.3 µmol l-1
(B), 3.0 µmol l-1 (C) and 30.0 µmol l-1 (D)
nocodazole. Nocodazole largely prevented macrostomes from forming more than
one digestive vacuole. In all experiments, the concentration of T.
thermophila was 105 cells ml-1. The experiment was
repeated three times, and 100 microstomal cells were counted in each
experiment. Values are expressed as the mean + S.E.M.
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© The Company of Biologists Ltd 2002
