Ref ID : 1187
Klaus Hausmann and Robert K. Peck; The mode of function of the cytopharyngeal basket of the ciliate Pseudomicrothorax dubius. Differentiation 14:147-158, 1979
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The ciliate Pseudomicrothorax dubius feeds on filamentous blue-green algae, ingesting them at rates of up to 15 um per second, by means of a cytopharyngeal basket. The wall of the basket is composed of 22+/-3 nemadesmata, each of which is a bundle of about 200 microtubules which are cross-linked in a hexagonal pattern. The lumen of the non-feeding basket is filled with cytoplasma into which project the nemadesmal lamellae. Each nemadesmal lamella is attached to a nemadesm and consists of a single row of 20-30 microtubules. Each microtubule of the nemadesmal lamella bears a row of pairs of arm-like projections which are embedded in a filamentous matrix. During feeding, the lumen of the basket is occupied by the developing food vacuole. The nemadesmal lamellae are observed between the vacuole membrane and the nemadesmata, and the arms of the nemadesmal lamellae microtubules are oriented toward the membrane of the food vacuole or of small vesicles. A mechanism for the generation of force for phagocytosis by means of the microtubule arms is proposed. During food uptake the membrane of the food vacuole increases rapidly at rates up to 270 um2 per second. Vacuole growth results from the fusion of membrane-bound vesicles. During phagocytosis a fast streaming of these vesicles can be observed in the cytoplasm surrounding the basket. The direction of streaming is opposite to that of ingestion of the algal filament. The vesicles enter the lumen of the basket at its anterior end, in a zone where the wall of the basket is perforated.