| Author Title Journal |
Bock H (1936) Lichtruckeneinstellung und andere lokomotorische Lichtreaktionen bei Planaria gonocephala. Zool Jahrb Abt Allg Zool U PHYSIOL 56(4): 501-530 |
Abstract / Notes
Planarians put between glass plates and lighted ventrally turn their dorsal surfaces to the light regardless of the direction of gravity, but the effect of gravity is evidenced in that the reaction is slowed when the light is below. Unilateral blinding has no effect. Bilateral extirpation of the eyes does not inhibit the reaction, since planarians have a general sensitivity to light, but the effect of gravity is more pronounced. After decapitation the worms move slowly and no longer turn the dorsal surface to the light; gravity also plays no directive role. On a vertical glass rod, the worms turn the dorsal surface to a single horizontal light. If the rod is lighted from 2 or 3 sides, the worms usually react to 1 light and disregard the others, and may react to the different lights one after the other. Sometimes the worms may react to 2 lights simultaneously by testing movements of the head towards them. Unequal intensities in the ratio of 1:4 do not evoke any inequality of reaction. Worms with 1 eye removed at first tend to move towards the intact side when on the glass rod but later react like normal worms. Worms with both eyes removed behave like normals on the rod; after decapitation the dorsal surface is no longer turned towards the light. Upon an equally lighted surface the worms wander without direction but some individuals move in spirals. After removal of 1 eye, most of the worms tend to curve towards the intact side. When horizontally lighted from one side, the worms show no exact orientation but either avoid the light or circle around it; with 2 or 3 horizontal lights, the results were similar, the worms reacting to only 1 light at a time. In onesided horizontal light, unilaterally blinded worms at first tend to move in curves and spirals but later react like normals as do also bilaterally blinded worms. Decapitated worms in 1-sided horizontal light move away from the light. Double monsters were obtained by splitting worms from the tail forward nearly to the head; in the angle of the 2 tails another head forms. Such monsters behave like 2 individuals; first one dominates, then the other. In an evenly lighted field, such worms spiral towards the subordinate side and in moving away from a light they also usually spiral. Struggle for dominance between the 2 components interferes with light reactions. Removal of the eyes or decapitation of 1 component does not put it under control of the other.| Home page -- (Main hierarchy) |