Laboea strobila was isolated by A. Beran from a plankton sample taken in February 2002 in the Gulf of Trieste (Northern Adriatic; ~45°42’N 13°42’E). The ciliates were transferred from the sample into sterile culture medium A (Table 1) and washed twice to minimize the initial contamination by other organisms. Clonal cultures were established in sterile, HCl-washed glass bowls (Arcoroc, France) containing 5 ml of medium enriched with Isochrysis galbana and an unidentified cryptophyte as food; the bowls were covered by a Petri dish. The cultivation temperature was kept close to that of the sample (10 °C vs. 7 °C). Weekly, ~100 ciliates were transferred from the growing clonal cultures into bowls (pre-treatment, see above) with 20 ml of medium and food algae. The cultures were checked microscopically at intervals for eventual growth of bacteria and or degradation of ciliates and food. No attempt was, however, made to keep the cultures bacteria-free because the cryptophytes needed bacteria. Parallel cultures were maintained at 15.5 °C. Food algae were sustained as batch cultures in 100 ml borosilicate Erlenmeyer flasks with 50 ml medium B (Table 1) at 15.5 °C. All organisms were cultured at a 10 h dark to 14 h light cycle with an irradiance of ~10 μE m−2 s−1 for L. strobila and the cryptophyte and ~50 μE m−2 s−1 for I. galbana.
The other populations of L. strobila were collected by the senior author in the harbour of List, Island of Sylt (German North Sea coast; ~55°01′N 08°27′E) and in the Irish Sea near the Port Erin Marine Laboratory, Isle of Man (~54°05′N 04°45′W).