The chemical defense/offense in ciliated protists by means of toxic secondary metabolites.

Several species of protists developed a number a different strategies intended to improve prey capture or avoid the predation. Particularly, in ciliated protist, the predator-prey interactions are often mediated by means some peculiar ejectable membrane-bound organelles generally called extrusomes. These organelles are usually localized in the cell cortex and attached to the cell membrane, sharing a common characteristic in discharging their contents to the outside of the cell in response to different stimuli. Some of these extrusomes are known to function as defensive organelles as the cortical granules in Climacostomum virens; others were demonstrated to have an offensive function (such as the toxicysts in raptorial ciliates, for example in Colpes hirtus), but the role of many other extrusomes remain unknown. Several of these extrusomes are known to produce toxic secondary metabolites that have been isolated from ciliates, and many of these molecules seem to be the result of evolutionary selection related to defense and/or predatory mechanisms. To date, only few of these molecules have been deep studied in function and biological activities, and include keronopsin isolated from Pseudokeronopsis rubra, euplotins from Euplotes species, blepharismins from Blepharisma japonicum, stentorin from Stentor coeruleus and climacostol from Climacostomum virens.