ESTIMATION OF AMEBA CELL-VOLUME FROM NUCLEAR DIAMETER AND ITS APPLICATION TO STUDIES IN PROTOZOAN ECOLOGY

To facilitate the estimation of cell volume in uninucleate, naked amoe bae (gymnamoebae) the relationship, log cell volume (mum3) = 0.882 + 3 .117log nuclear diameter (mum3), is presented. This links mean cell vo lume to mean nuclear diameter and provides a useful tool for protozoan ecologists interested in estimating the biovolume of amoebae in labor atory or field samples. While it is virtually impossible to measure ri gid axes from which volume can be calculated in these amorphous cells, it is relatively easy to measure the diameter of the nucleus in livin g or fixed material. This relationship has shown that most uninucleate amoebae surveyed have volumes ranging between only 188 mum3 and 2860 mum3; this range reflects the volumes of the majority of amoebae in th e field. These small volumes are unexpected since many amoebae have lo comotive forms greater than 20 mum in length giving the impression tha t their cell volumes should be correspondingly large. This is not the case, however, because most amoebae are extremely flat when viewed in profile. The small cell volume of most amoeba species has ecological i mplications when numerical data is transformed to biovolume and biomas s units.