title: The ratio of extracellular Ca2+ to K+ ions affects the photoresponses in Stentor coeruleus.
abstract: 1. Stentor coeruleus exhibits negative phototaxis (due to phototactic orientation response) and step-up photophobic response (avoiding reaction) to visible light. 2. The effect of Ja-value ([K+]/[Ca2+]1/2) and calcium ion concentration of the surrounding medium on the photoresponses in Stentor were studied. 3. The both types of photoresponses in Stentor are greatly affected by the Ja-value. A higher Ja-value medium suppressed the step-up photophobic response of Stentor, whereas the organism showed a higher degree of phototactic orientation response in higher Ja-value solutions. 4. The effect of the Ja-value on the step-up photophobic response was opposite to that on the phototactic orientation response. 5. With increasing calcium concentration but at a constant Ja-value, the number of Stentor showing the step-up photophobic response increased, whereas the phototactic orientation response of Stentor was suppressed at higher Ca2+ concentrations. 6. The effect of the calcium concentration on the photophobic response was also opposite to that on the phototactic orientation response, as in the case of Ja-value effect.
authors.affiliation: Tsukuba Life Science Laboratory, Nippon Petrochemicals Co., Ltd, Ibaraki Japan.
authors.forename: K
authors.initials: K
authors.lastname: Iwatsuki
authors.forename: P S
authors.initials: PS
authors.lastname: Song
mesh_terms: D000818:Animals; D001362:Avoidance Learning; D002118:Calcium / Q000378:metabolism*; D002923:Cilia / Q000502:physiology; D056890:Eukaryota / Q000378:metabolism / Q000528:radiation effects*; D005110:Extracellular Space / Q000378:metabolism*; D007477:Ions; D008027:Light; D009068:Movement / Q000528:radiation effects; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism*; D013550:Swimming
chemical_list: D007477:Ions; D011188:Potassium; D002118:Calcium