Gamones are secreted in Euplotes octocarinatus via the cortical ampules

The releasing sites of the gamones and their intracellular localization were investigated in Euplotes octocarinatus with the help of a polyclonal antibody labeled by protein A-gold. The antibody was raised against secreted gamone 1 that had been purified from the culture medium of a cell line homozygous at the mating type locus for the allele mt(1). ELISA tests demonstrated that the antibody binds to gamones 1 and 2 but not to gamones 3 and 4. Therefore cells homozygous for mt(3), releasing gamone 3, could be used as controls in attempts to localize gamone 1 in ultrathin sections of appropriate cells. The protein A-gold labeled antibody allowed detection of gamone 1 in cytoplasmic cisternae, in small and large cytoplasmic vesicles and in cortical ampules of cells homozygous for mt(1). We suggested the cortical ampules are the releasing sites of the Euplotes gamones and that they are stored in vesicles that fuse with the ampules.