title: Transitions in Dictyostelium discoideum behaviour: influence of calcium and fluoride on slug phototaxis and thermotaxis.
abstract: Phototaxis and thermotaxis by slugs of Dictyostelium discoideum show transitions that result in bimodality in phototaxis and temperature-dependent orientation up or down temperature gradients. New steps in the sensory transduction chain for these kinds of behaviour are elucidated from studies using inorganic salts (Ca2+, EGTA, KF) and several mutants. KF enhances bimodality of phototaxis, improves the accuracy of thermotaxis, and affects the transition temperatures from positive to negative thermotaxis. Changing the Ca2+ concentration has effects on both phototaxis and thermotaxis. At low Ca2+ concentrations phototaxis and thermotaxis are enhanced. In the presence of EGTA or high concentrations of Ca2+ phototaxis becomes bimodal, thermotaxis is impaired and spontaneous turning is suppressed. These results obtained by changing Ca2+ concentrations are analogous to those obtained previously with sensory transduction mutations, which coordinately affect phototaxis and thermotaxis.
mesh_terms: D000362:Agar; D002118:Calcium / Q000494:pharmacology; D004023:Dictyostelium / Q000187:drug effects / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology; D006358:Hot Temperature; D008027:Light; D009068:Movement / Q000187:drug effects
chemical_list: D004533:Egtazic Acid; D000362:Agar; D005459:Fluorides; D002118:Calcium