Trichocysts of Paramecium: Secretory organelles in search of their function.

Possible function(s) proposed in the literature for Paramecium trichocysts have been controversial for a long time. The oldest hypothesis, defence against protozoan predators, has now obtained support from experiments with Dileptus as well as by our observation of a vigorous lateral displacement of cells due to synchronous, massive local trichocyst expulsion. Recently discovered secretory lectins could also operate in defence or improve the availability of food organisms. Other hypotheses on trichocyst function - even if they appeared unlikely to us a priori-have also been analyzed experimentally, but no convincing evidence in favour of any of them could be found.