A Retaliatory Role for Algal Projectiles , with Implications for the Mechanochemistry of Diatom Gliding Motility

It is shown that the projectiles ejected by discobolocysts in the single-celled Chry-sophyceaen alga Ochromonas tuberculatlls travel at speeds of up to 0.26 km/s, as fast as a bullet from a low power rifle. They may thus inflict damage to a would-be predator. Their Reynolds number is high..around 100, far from the low Reynolds numbers presumed typical of cellular evertts. Hydration of the mucopolysaccharide in discobolocysts, by one to three hydrogen bonds per monomer, is shown to be a sufficient source of energy for this mechanochemical reaction. The hydrogen bonding appears to induce a conformational change, ratherthan swelling of the mucopolysac-charide. It is also shown that the same degree of hydration of mucopolysaccharides would provide sufficient motive force to explain the gliding motility of rJphid diatoms, when incorporated into the capillarity model for diatom locomotion. The efficiency of the diatom's mechanochemical raphe system may be as high as 99%. The microfilament bundles adjacent to the raphe inside the cell may control forward, stop and reverse functions by a sliding mechanism.