Growth and grazing responses to temperature and prey concentration of Condylostoma spatiosum, a large benthic ciliate, feeding on Oxyrrhis marina

Abstract

Condylostoma is as a group of very large-sized ciliates frequently dominant in various marine benthic microbial communities. However, little is known about the effects of temperature and food concentration on its growth and grazing. Here, using the heterotrophic dinoflagellate Oxyrrhis marina as prey, we determined the specific growth rate, cell volume, specific production, and ingestion rate of C. spatiosum at different temperatures and prey concentrations. These growth and grazing parameters typically followed a hyperbolic response to prey concentration. By applying iterative curve-fitting to the data at each temperature, we found that, with increasing temperature, the maximum specific growth rate, maximum specific production, and maximum ingestion rate of C. spatiosum generally increased, while the maximum cell volume decreased. The gross growth efficiency of C. spatiosum generally decreased at saturated prey concentration from about 45 to 25% as the temperature increased from 12 to 24 degrees C. By fitting these data iteratively to multi-variable nonlinear models, we obtained predictive equations for the growth rate, cell volume, and ingestion rate with respect to temperature and prey concentration.