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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 1656

Jeffrey D. Jack and John J. Gilbert; The effect of suspended clay on ciliate population growth rates. Freshwater Biology 29:385-394, 1993

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1. Renewed batch cultures on three algiovorous and one bacterivorous ciliate showed that ciliate reproductive rates increase with increasing food concentration up to an asymptote. Maximum (rm) values for Strobilidium gyrans, Bursaridium difficile and Euplotes eurystomus feeding on the cryptomonad alga Rhodomonas minuta were 0.87, 0.86 and 0.45 day-1, respectively, while Paramecium aurelia feeding on the bacterium Enterobactor aerogenes had an (r(m)) of 0.40 day-1. B. difficile had a food threshold (r(m)=0) of 0.38 µgC ml-1 and P. aurelia had a threshold of 1.6 µgC ml-1. 2. The presence of suspended fine (particle size <1 µm) and coarse (particle size 1-2 um) clay suppressed the half maximum reproductive rate of the ciliate Strobilidium gyrans by up to 69% but had no effect on B. difficile, E. eurystomus or P. aurelia. Populations of ciliates unaffected by clay may be released in situations where suspended particles negatively affect their metazooplankton predators and competitors.