Responses of three freshwater planktonic ciliates with different feeding modes to cryptophyte and diatom prey

Abstract

The filter feeding oligotrich ciliate Strobilidium lacustris, the raptorial prostome ciliate Balanion planctonicu~n and the diffusion feeding scuticociliate Histiobalantium bodamicurn could be cultivated for months/years on a sole &et of Cryptomonas sp., whereas the diatom Stephanodiscus hantzschii did not support their growth. With Cryptornonas sp. as food, numerical responses of all ciliates followed a modified Michaelis-Menten model, which at lS°C yielded maximum growth rates of 0.96. 1.87 and 0.33 d-' and threshold concentrations of 61, 7 8 and 290 ng C ml-' for S. lacustris, B. planctonicum and H. bodamicum, respectively. Functional response patterns differed between species. In all investigated ciliates, growth rates reached a maximum earlier than ingestion rates, and there were no threshold concentrations for zero ingestion. Food selectivity depended on feeding mode. H. bodamicum was not able to ingest the non-motile diatoms. Both S. lacustris and B. planctonicum selectively preferred cryptophytes when offered a mixed diet. This effect was more pronounced in the raptorial feeder compared to the filter feeder. Our results indicate that during the phytoplankton spring bloom in Lake Constance prostome and oligotrich ciliates mainly exploit cryptophytes, and that the scuticociliate H. bodamicum, due to its slow growth, is an inferior competitor during this season. The observed threshold concentrations suggest that during the rest of the year prostomes and oligotrichs must rely on small-scale patches of this food, whereas H. bodamicum, with maximum development in late summer and autumn, presumably consumes a much larger variety of prey.

Meseres corlissi: a rare oligotrich ciliate adapted to warm water and temporary habitats

“…The numerical and functional response curves further demonstrate that M. corlissi should be highly competitive in many warm-temperate and (sub)tropical lakes. The threshold food concentration for population growth is comparable to that of other planktonic ciliate species obtained under similar food and temperature conditions (Müller & Schlegel 1999, Weisse et al 2002, but at the high end of values reported for oligotrich ciliates (Jakobsen & Hansen 1997 and references therein, Montagnes & Lessard 1999, Müller & Schlegel 1999. The threshold level corresponds to a chlorophyll a concentration of approximately 2.5 µg l -1 , assuming a carbon to chlorophyll a ratio of 40:1 (Banse 1977, Montagnes et al 1994), or to a bacterial abundance of 2 to 10 × 10 9 cells l -1…”

Spring bloom succession, grazing impact and herbivore selectivity of ciliate communities in response to winter warming

“…An analysis of long-term plankton data in the North Sea showed similar patterns for mesozooplankton communities as shifts in species composition and increases in diversity were observed (Beaugrand 2004;Hays et al 2005). However, Irigoien et al (2004) characterized microzooplankton diversity predominantly as a unimodal function of phytoplankton biomass, and ciliates are known to show a high species specificity regarding food concentrations, feeding preferences and temperature requirements (Mueller and Schlegel 1999;Weisse et al 2001). Thus, it can be assumed that the combined effect of temperature, food supply and food composition might be responsible for the high diversity in the warmer set-ups.…”

Phagotrophic ciliates and flagellates in an oligotrophic, deep, alpine lake: contrasting variability with seasons and depths

“…The food vacuoles of, e.g., Rimostrombidium lacustris or R. humile were densely packed with centric diatoms. Müller and co-workers (Müller 1989, Müller et al 1991b, Müller & Schlegel 1999 observed that the spring assemblage of Lake Constance (mainly B. planctonicum and Rimostrombidium spp.) was closely related to food resources and able to respond rapidly to a bloom of small phytoplankton.…”

“…At this time of the year, ciliates might be strong competitors with metazoan organisms, due to low generation times; hence, ciliates like B. planctonicum were assumed to be important contributors to the beginning of the so-called clearwater phase in meso-to eutrophic lakes, in addition to rotifers and other ciliates (Sommaruga & Psenner 1993. Generally, they were among the first grazers of algal biomass in spring, with a preference for cryptophytes (Carrick & Fahnenstiel 1989, Müller et al 1991b, Müller & Schlegel 1999.…”