ABSTRACT: This is the first study to consider the growth and feeding rates of naked marine amoebae at temperatures below 5°C. Specific growth rates were calculated for 5 Antarctic isolates, Platyamoeba australis, Mayorella sp., Metachaos sp., Vannella sp., and an unidentified vahlkampfiid amoeba. Growth rates ranged between 0.08 x 10^-2 and 2.9 x 10^-2 h^-1 corresponding to generation times of 866.2 and 23.9 h, respectively. All isolates grew at temperatures down to -2°C and showed optimal growth at 2°C although one species grew best at 0°C. A direct counting method was used to estimate bacterial feeding rates of P. australis and the vahlkampfiid amoeba. Rates varied as a function of prey density but were largely independent of temperature. Overall, amoebae consumed between 0.5 and 66.4 bacteria amoeba^-1 h^-1, equivalent to 0.3 and 38.0 pg C cell^-1 h^-1. Growth efficiencies estimated for these 2 amoebae were low, typically <2%, suggesting that amoebae incur high energetic costs for life at low temperatures.

KEY WORDS: Gymnamoebae · Protozoa · Generation times · Feeding · Growth efficiencies

Published in MEPS Vol. 160 (1997) on December 15
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1997