Interspecific morphogens regulating prey-predator relationships in protozoa.

The ciliate Euplotes octocarinatus and some close relatives of it are triggered by predator-released substances to undergo morphogenetic changes that inhibit their engulfment. The changes occur within a few hours and do not require cell division. They are perpetuated during reproduction so long as the concentration of the morphogen is maintained. The ability of Euplotes to respond to predator-produced signals by a defensive change in cell architecture probably provides an effective mechanism for damping population oscillations ofboth prey and predators andfosters coexistence. The signal-induced cell transformation merits study for its own sake because of its developmental implications.