Further studies on respiratory rates of freshwater amoebae (Rhizopoda, Gymnamoebia)

Abstract

The respiration rates of axenically culturedAcanthamoeba castellanii (Gymnamoebia) and of the test organismTetrahymena pyriformis (Ciliophora) were compared using both Warburg and cartesian diver respirometer techniques at 20°C. Furthermore, the latter procedure was employed to measure the oxygen consumption of the amoebae,Polychaos fasciculatum, Saccamoeba limax, andAmoeba sp. The linear relationship between respiration rate and mean cell volume in amoebae was reassessed in view of these additional estimates. The importance of this regression in ecological studies is discussed.

Estimation of amoeba cell volume from nuclear diameter and its application to studies in protozoan ecology

“…1). This is similar to the published value of 21500 /m 3 based on cell parameter measurements (Baldock et al, 1982). If application of the relationship to other protozoa is justified, then the common practice of counting protozoa by fluorescence microscopy in conjunction with DNA-fluorochromes could yield additional information on the total biovolume of heterotrophic protozoa in a sample.…”

“…Before this new data on amoebae can be used to answer questions about the flow of material through populations in the field, abundances must first be transformed to equivalent biovolume units (m 3 ) and biological conversion constants employed. Accurate cell volume determinations are also required when workers wish to use the available published relationships for protozoa linking, for example, cell volume to reproductive rate (Fenchel, 1968;Finlay, 1977;Baldock et al, 1980) and cell volume to respiration rate (Fenchel & Finlay, 1983;Baldock et al, 1982).…”

“…The usual approach for determining cell volume in other groups of protozoa is to measure definable cell dimensions, such as maximum length and width, and to compute volume from the closest geometric shape. To take a popular example, published volume estimates for the ciliate Tetrahymena have used the assumption that cell shape approximates an ellipsoid or prolate spheroid (Curds & Cockburn, 1971;Rogerson, 1981;Baldock et al, 1982). Unlike the fixed cell shape of most flagellates and ciliates, amoebae have plastic cell morphologies, frequently with a raised cell mass surrounded by flattened hyaline zones and radiating pseudopodia.…”

“…This is, however, inappropriate for the majority of amoebae and only yields an approximation of cell volume. Others have fixed amoebae in Lugol's iodine or Bouin's solution (Baldock et al, 1982), a procedure which makes a small percentage of the population form spherical cells with only minor shrinkage. However, this method cannot be used for field samples where most living or fixed amoebae are overlooked, in cases where amoebae do not round-up in the fixative, or for species which cannot be cultivated in the laboratory.…”

Respiration of the marine amoeba Trichosphaerium sieboldi determined by 14C labelling and Cartesian diver methods

“…Baldock et al 1982) and frequently include microbial contaminants which also affect the measured respiration rate. Diver microrespirometry has been used to overcome these shortcomings, to some extent, in that a few cells can be isolated and washed free of contaminating organisms prior to placing in the diver.…”