The role of flagellar adhesion in sexual activation ofChlamydomonas eugametos

Summary Sex-specific agglutination in gametes ofChlamydomonas eugametos was carried out with dead partner cells (killed by glutaraldehyde, formaldehyde or OsO₄), with isolated flagella, flagellar appendages and isoagglutinins derived from cell-free culture medium. The activation of the plasma papilla in agglutinated cells was studied by scanning electron microscopy in relation to the agglutinative properties of the materials tested. The results reveal differences in agglutination and papilla activation between gametes of both mating types. They also indicate that papilla activation depends on the extent of agglutination, which is a function of sex-specific flagellar properties and the amount and nature of the agglutinative material used. A hypothesis is presented to explain the observed phenomena.