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Spontaneous Behaviors and Wall-Curvature Lead to Apparent Wall Preference in Planarian.

Akiyama Y, Agata K, Inoue T - PLoS ONE (2015)

Bottom Line: When we tested another spontaneous behavior, the wigwag movement of the planarian head, using computer simulation with various wigwag angles and wigwag intervals, large wigwag angle and short wigwag interval reduced wall-preference behavior.Furthermore, in accord with this simulation, when we tested planarian wall-preference behavior using several assay fields with different curvature of the wall, we found that concavity and sharp curvature of walls negatively impacted wall preference by affecting the permissible angle of the wigwag movement.Together, these results indicate that planarian wall preference may be involuntarily caused by the combination of two spontaneous planarian behaviors: moving straight ahead until reaching a wall and then moving along it in the absence of environmental cues, and wigwag movements of the head.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.

ABSTRACT
The planarian Dugesia japonica tends to stay near the walls of its breeding containers and experimental dishes in the laboratory, a phenomenon called "wall preference". This behavior is thought to be important for environmental adaptation, such as hiding by planarians in nature. However, the mechanisms regulating wall-preference behavior are not well understood, since this behavior occurs in the absence of any particular stimulation. Here we show the mechanisms of wall-preference behavior. Surprisingly, planarian wall-preference behavior was also shown even by the head alone and by headless planarians. These results indicate that planarian "wall-preference" behavior only appears to be a "preference" behavior, and is actually an outcome of spontaneous behaviors, rather than of brain function. We found that in the absence of environmental cues planarians moved basically straight ahead until they reached a wall, and that after reaching a wall, they changed their direction of movement to one tangential to the wall, suggesting that this spontaneous behavior may play a critical role in the wall preference. When we tested another spontaneous behavior, the wigwag movement of the planarian head, using computer simulation with various wigwag angles and wigwag intervals, large wigwag angle and short wigwag interval reduced wall-preference behavior. This indicated that wigwag movement may determine the probability of staying near the wall or leaving the wall. Furthermore, in accord with this simulation, when we tested planarian wall-preference behavior using several assay fields with different curvature of the wall, we found that concavity and sharp curvature of walls negatively impacted wall preference by affecting the permissible angle of the wigwag movement. Together, these results indicate that planarian wall preference may be involuntarily caused by the combination of two spontaneous planarian behaviors: moving straight ahead until reaching a wall and then moving along it in the absence of environmental cues, and wigwag movements of the head.

No MeSH data available.


Related in: MedlinePlus

Schematic illustration of planarian apparent wall preference.Planarians basically move straight ahead in an open field until reaching a wall. Planarians can easily leave the wall within a short time while moving along a convex curve because they can keep going straight ahead. In contrast, the possible direction of a planarian movement is limited for planarians moving around a concave curve of a wall. Planarians can leave a wall only when their wigwag angle is larger than the angle of curvature, and the frequency of this is stochastically low. If planarians display only a small angle of wigwag movements, they continue to move along the wall for a while, and then stop moving and stay motionless near the wall in the absence of environmental stimuli.
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pone.0142214.g007: Schematic illustration of planarian apparent wall preference.Planarians basically move straight ahead in an open field until reaching a wall. Planarians can easily leave the wall within a short time while moving along a convex curve because they can keep going straight ahead. In contrast, the possible direction of a planarian movement is limited for planarians moving around a concave curve of a wall. Planarians can leave a wall only when their wigwag angle is larger than the angle of curvature, and the frequency of this is stochastically low. If planarians display only a small angle of wigwag movements, they continue to move along the wall for a while, and then stop moving and stay motionless near the wall in the absence of environmental stimuli.

Mentions: Taken together, our observations and simulations indicate that planarians move straight ahead in the absence of environmental cues, and they would continue to attempt to move straight ahead even after reaching a wall, and as a result, they move along walls for a certain time (Fig 7). When a planarian wigwag angle, which varies stochastically, is greater than the angle of the wall's curvature, the planarian leaves the wall (Fig 7). The planarian would then stop moving, and therefore would stay motionless near the wall.


Spontaneous Behaviors and Wall-Curvature Lead to Apparent Wall Preference in Planarian.

Akiyama Y, Agata K, Inoue T - PLoS ONE (2015)

Schematic illustration of planarian apparent wall preference.Planarians basically move straight ahead in an open field until reaching a wall. Planarians can easily leave the wall within a short time while moving along a convex curve because they can keep going straight ahead. In contrast, the possible direction of a planarian movement is limited for planarians moving around a concave curve of a wall. Planarians can leave a wall only when their wigwag angle is larger than the angle of curvature, and the frequency of this is stochastically low. If planarians display only a small angle of wigwag movements, they continue to move along the wall for a while, and then stop moving and stay motionless near the wall in the absence of environmental stimuli.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4635015&req=5

pone.0142214.g007: Schematic illustration of planarian apparent wall preference.Planarians basically move straight ahead in an open field until reaching a wall. Planarians can easily leave the wall within a short time while moving along a convex curve because they can keep going straight ahead. In contrast, the possible direction of a planarian movement is limited for planarians moving around a concave curve of a wall. Planarians can leave a wall only when their wigwag angle is larger than the angle of curvature, and the frequency of this is stochastically low. If planarians display only a small angle of wigwag movements, they continue to move along the wall for a while, and then stop moving and stay motionless near the wall in the absence of environmental stimuli.
Mentions: Taken together, our observations and simulations indicate that planarians move straight ahead in the absence of environmental cues, and they would continue to attempt to move straight ahead even after reaching a wall, and as a result, they move along walls for a certain time (Fig 7). When a planarian wigwag angle, which varies stochastically, is greater than the angle of the wall's curvature, the planarian leaves the wall (Fig 7). The planarian would then stop moving, and therefore would stay motionless near the wall.

Bottom Line: When we tested another spontaneous behavior, the wigwag movement of the planarian head, using computer simulation with various wigwag angles and wigwag intervals, large wigwag angle and short wigwag interval reduced wall-preference behavior.Furthermore, in accord with this simulation, when we tested planarian wall-preference behavior using several assay fields with different curvature of the wall, we found that concavity and sharp curvature of walls negatively impacted wall preference by affecting the permissible angle of the wigwag movement.Together, these results indicate that planarian wall preference may be involuntarily caused by the combination of two spontaneous planarian behaviors: moving straight ahead until reaching a wall and then moving along it in the absence of environmental cues, and wigwag movements of the head.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwake, Sakyo-ku, Kyoto, Japan.

ABSTRACT
The planarian Dugesia japonica tends to stay near the walls of its breeding containers and experimental dishes in the laboratory, a phenomenon called "wall preference". This behavior is thought to be important for environmental adaptation, such as hiding by planarians in nature. However, the mechanisms regulating wall-preference behavior are not well understood, since this behavior occurs in the absence of any particular stimulation. Here we show the mechanisms of wall-preference behavior. Surprisingly, planarian wall-preference behavior was also shown even by the head alone and by headless planarians. These results indicate that planarian "wall-preference" behavior only appears to be a "preference" behavior, and is actually an outcome of spontaneous behaviors, rather than of brain function. We found that in the absence of environmental cues planarians moved basically straight ahead until they reached a wall, and that after reaching a wall, they changed their direction of movement to one tangential to the wall, suggesting that this spontaneous behavior may play a critical role in the wall preference. When we tested another spontaneous behavior, the wigwag movement of the planarian head, using computer simulation with various wigwag angles and wigwag intervals, large wigwag angle and short wigwag interval reduced wall-preference behavior. This indicated that wigwag movement may determine the probability of staying near the wall or leaving the wall. Furthermore, in accord with this simulation, when we tested planarian wall-preference behavior using several assay fields with different curvature of the wall, we found that concavity and sharp curvature of walls negatively impacted wall preference by affecting the permissible angle of the wigwag movement. Together, these results indicate that planarian wall preference may be involuntarily caused by the combination of two spontaneous planarian behaviors: moving straight ahead until reaching a wall and then moving along it in the absence of environmental cues, and wigwag movements of the head.

No MeSH data available.


Related in: MedlinePlus