The behaviour of an omnivorous protozoan affects the extent of induced morphological defence in a protozoan prey

Summary 1. The ciliate Euplotes octocarinatus responds to the presence of Stylonychia mytilus with a morphological transformation rendering its ingestion more difficult. Predation on Euplotes is reduced when an alternative prey, the flagellate Chlorogonium elongatum, is available. Lower predation is...

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Bibliographic Details
Published in:Freshwater biology 2004-06, Vol.49 (6), p.801-809
Main Authors: Wia˛ckowski, Krzysztof, Fyda, Janusz, Ciećko, Aneta
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
Biological and medical sciences
Chlorogonium elongatum
ciliates
Euplotes octocarinatus
Fresh water ecosystems
Freshwater
Fundamental and applied biological sciences. Psychology
inducible defences
predator-prey interaction
Protists
Stylonychia mytilus
Synecology
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Summary:Summary 1. The ciliate Euplotes octocarinatus responds to the presence of Stylonychia mytilus with a morphological transformation rendering its ingestion more difficult. Predation on Euplotes is reduced when an alternative prey, the flagellate Chlorogonium elongatum, is available. Lower predation is accompanied by reduced induction in Euplotes. 2. We quantified the motility of both ciliates in the presence and absence of Chlorogonium to test the hypothesis that the differential response in Euplotes is a consequence of behavioural changes affecting the encounter rate of the prey and the predator. 3. The results indicate that S. mytilus uses different feeding strategies for each prey. It is a filter feeder when small food particles (Chlorogonium) are abundant, however, it becomes a raptorial feeder when large prey with an escape capability (Euplotes) is available and small alternative prey are absent. 4. As the mobility of filter feeding Stylonychia is strongly limited, the presence of the flagellate may indirectly affect the defence level in Euplotes by reducing the frequency of contacts with the predator. 5. An experiment with Chaetogaster diastrophus, a more specialised predator not affected by the presence of Chlorogonium, as well as direct manipulation of the encounter rate by changing the surface area available for the crawling ciliates, supported the encounter rate hypothesis.
ISSN:0046-5070
1365-2427
DOI:10.1111/j.1365-2427.2004.01227.x