Role of soil in the life cycle of Meseres corlissi (Ciliophora: Oligotrichea): experiments with two clonal strains from the type locality, an astatic meadow pond

Abstract

The life cycle of the oligotrich ciliate Meseres corlissi was investigated using 2 clonal strains, E4 and M10, which were isolated from soil samples collected at the type locality in Salzburg, Austria, and grown in a 1:1 mixture of WC medium and Eau de Volvic on a diet of cryptomonads. Growth, encystment, excystment and cyst survival of both strains depended strongly on the presence or absence of soil components in the culture medium. (1) Growth was enhanced greatly by addition of soil extract or sterilized garden soil. (2) Encystment could be induced by dilution of soil extract concentrations, whereas dilution of ciliates or food algae, at a constant soil extract level, had no significant effect. A sudden decrease in temperature, however, inhibited the encystment reaction. (3) Excystment could be triggered by addition of soil extract or sterilized garden soil. (4) Resting cysts survived desiccation periods of > 7 d only in the presence of sterilized garden soil. The nature of the 'soil factor' responsible for these effects remains at present unknown. The growth and encystment responses of strains E4 and M10 differ clearly from those of the earlier investigated strain DR (Weisse 2004), which was isolated from the reservoir of a tree bromelia in the Dominican Republic. These differences are interpreted as local adaptations of 2 morphologically and genetically indistinguishable but geographically distant populations of a cosmopolitan but rare ciliate species.

Local adaptation among geographically distant clones of the cosmopolitan freshwater ciliate Meseres corlissi. II. Response to pH

“…at saturating concentrations in a cocktail composed of MWC medium, Eau de Volvic, and soil extract (SE, 5 to 10% by vol.). The SE was prepared from a commercial garden soil (Qualitäts-Pflanzenerde, SagaFlor) as described by Müller et al (2006). The pH of the suspension was adjusted by addition of small amounts of 0.1 mol l -1 NaOH or HCl.…”

“…Other obvious intraspecific differences in the life cycle of this species have been identified with respect to the factors that trigger its encystment and excystment (Müller et al 2006). Müller et al's (2006) study showed that the presence of soil or soil extract may be essential for sustained optimal growth and completion of the life cycle of at least some Austrian Meseres corlissi clones.…”

“…Müller et al's (2006) study showed that the presence of soil or soil extract may be essential for sustained optimal growth and completion of the life cycle of at least some Austrian Meseres corlissi clones. The freely swimming, trophic cells of M. corlissi reach growth and feeding rates that are among the highest hitherto recorded for aquatic ciliates (Weisse 2004(Weisse , 2006.…”

“…Recently, clonal differences in the temperature response and adaptation to the habitat temperature were demonstrated for the oligotrich ciliate Meseres corlissi Petz & Foissner 1992(Gächter & Weisse 2006). This ciliate has become a model organism for investigating local ecophysiological adaptation among cosmopolitan but rare freshwater ciliates (Weisse 2004, 2006, Müller et al 2006.…”

Local adaptation among geographically distant clones of the cosmopolitan freshwater ciliate Meseres corlissi. I. Temperature response

“…In the experiments with clone AU4, 5% soil extract (SE) were added to the medium (Müller et al 2006), since preliminary experiments (data not shown) had revealed that this strain requires SE for optimal growth in the culture flasks.…”