Main Content

The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3662

Jorgen Kusch and Hans-Werner Kuhlmann; Cost of Stenostomum-induced morphological defence in the ciliate Euplotes octocarinatus. Arch.Hydrobiol. 130(3):257-267, 1994

Reprint

In File

Notes

Several predatory organisms induce a defensive morphological response in the freshwater ciliate Euplotes octocarinatus. The morphological changes have demographic cost besides an adaptive advantage. The generation time of E. octocarinatus increased from 40+/-1 hr (SDM) to 47+/-2 hr when the ciliate changes its morphology in response to the presence of Stenostomum sphagnetorum (Turbellaria). It remained at a high level in the protective "winged" form of the ciliates (45+/-1 hr). The population growth rate therefore decreased by 15% (from r=0.60/day to r=0.51/day). When predators had disappeared the duration of the following reproduction cycle decreased to 38+/-1 hr. A longer growth phase of winged ciliates was related to their lowered reproduction rate. The length of the G1-phase of the cell cycle increased from 25+/-1 hr to 34+/-2 hr (SD); the length of the S phase remained constant (13+/-1 hr or 12+/-3 hr). Synthesis of proteins was necessary for predator-induced morphological changes. The protein content of Euplotes octocarinatus increased from 1.1+/-0.1 pg/ciliate to 1.7+/-0.2 pg (SD) during morphological transformation. The protein synthesis inhibitor cycloheximid (>/_50 µM) inhibited morphological changes. These results indicate that additional growth of the ciliate is necessary for morphological changes. The growth process leads as a cost to an increased generation time of Euplotes. The feeding rate of winged forms of the ciliate had slightly increased compared to the feeding rate of the typical form. Therefore, food limitation is not crucial of the cost of predator-induced defence; however, it may be beneficial for the winged form.