Behavioral studies into the mechanism of eukaryotic chemotaxis

Recent behavioral studies designed to elucidate the mechanism of chemotaxis to cAMP in the eukaroyteDictyostelium discoideum are reviewed. In these studies, ambae were analyzed by the newly developed, computer-assisted dynamic morphology system while (1) chemotaxing in a spatial gradient of cAMP, (2) responding to repeated temporal waves of cAMP in the absence of a spatial gradient in a Sykes-Moore chamber, and (3) responding to rapid shifts in cAMP concentration. It is demonstrated that eukaryotic amebae do indeed have the capacity to assess the direction of a temporal gradient, which indicates that they must have a "memory" system for this purpose. It is also demonstrated that amebae regulate behavior in spatial and temporal gradients of chemoattractant through changes in: (1) velocity; (2) frequency of pseudopod formation; and (3) frequency of turning. Analogies to the bacterial system are apparent.