The Use of a Protozoan for Studies on Ageing

Abstract

Tokophrya inf usionum a protozoan from the class Suctoria is able to feed without interruption if food is available. A constantly feeding Tokophrya acquires giant proportions and has a greatly reduced life span. A comparative study of young overfed and old normally fed Tokophrya showed remarkable similarities between the 2 groups of organisms. It was found that the functional efficiency of the tentacles and of the reproductive capacity decreases greatly, and finally stops completely in both, the young overfed and in the old normally fed organisms. In electron microscopy large vacuoles filled with small particles about 300 A in diameter were found in both groups and also lipid-like pigment bodies similar to the old age pigment. Both structures are regarded as insoluble waste products. The cytoplasmic orga-nelles decrease in relative numbers in the young overfed as well as in the old normally fed organisms. In both the macronucleus is large (over 20 [mu] in diameter), irregular in shape, hyperpolyploid and unable to reproduce, unless hemixis takes place, a reorganization process leading to the division or fragmentation of the macronucleus. All the above enumerated similarities, together with the fact that the young overfed organism has a drastically reduced life span, lead to the conclusion that the chronologically young overfed organism is a pre -maturely aged, thus physiologically old, animal.