An Optical Model for Phototactic Orientation in Dictyostelium discoideum Slugs

概要

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The optical properties of an enlarged optical model of the tip of a slug (a glass tube filled with sucrose solution) of Dictyostelium discoideum were studied to validate the hypothesis that the organism orients itself with respect to lateral light using a lens effect: Light is focussed by refraction onto the distal side of the slug where the higher "signal" compared to the front side causes a turn toward the light. Light was effectively focused even when the model deviated only as little as 10゜ from the light direction. Slugs of D. discoideum strains HO596 and HO813 show bidirectional phototaxis: They orient themselves at some angle on either side of the incident light beam. This angle is 〜80゜ in HO596 and 〜70゜ in HO813. We suggest that this phenomenon can be explained by the optical properties of the slug such as absorption and scattering, shape of the tip or location and extension of the light-sensitive zone. The angle of orientation with respect to light is regulated by a balance between a turn toward and a turn away from the light direction.
日本植物生理学会の論文