ISSN:
1574-6941
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Abstract: The feeding of the marine ciliate Euplotes mutabilis was studied using bacteria (Vibrio natriegens) doubly labelled with 3H-thymidine and 14C-leucine. In the presence of abundant bacteria (30 × 106 bacteria ml−1), an average Euplotes cell (initially without food vacuoles) with a protein content of 12 ng consumed 16 × 103 bacteria in the first hour and 27 × 103 bacteria over four hours, accumulating about 60% of the bacterial protein into ciliate macromolecules. Euplotes which had been starved or under-fed to reduce cell protein biomass to 7 or 9 ng consumed significantly fewer bacteria, but the gross growth efficiency for protein did not change. The rate of consumption of bacteria by large Euplotes of protein content 15 ng was initially less than that of 12 ng cells, and it decreased markedly before the end of a 4-hour experiment. Recently divided cells ingested bacteria rapidly, but showed a reduced gross growth efficiency of about 40%. At low bacterial concentrations (6 × 106 bacteria ml−1) the rates of ingestion were markedly reduced to between 〈inlineGraphic alt="inline image" href="urn:x-wiley:01686496:FEM137:FEM_137_mu1" location="equation/FEM_137_mu1.gif"/〉 and 〈inlineGraphic alt="inline image" href="urn:x-wiley:01686496:FEM137:FEM_137_mu2" location="equation/FEM_137_mu2.gif"/〉 of maximal levels; the smallest cells could not sustain feeding activity at the low prey concentration and gross growth efficiency fell from 43 to 20% during a 4-hour experiment. The strategy adopted by Euplotes in response to local fluctuations in food supply involves rapid consumption with high growth efficiency in times of plenty, but slow shrinkage without cell division to survive in times of shortage.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1574-6941.1996.tb00312.x
