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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

Computer simulation of planarian spontaneous wigwag behavior.(A) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a rectangular field. Wigwag interval was generated by a random number generator whose probability density followed a log normal distribution with log mean of 0.14 sec and log standard deviation of 0.48. (B) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a circular field. (C) Wall-preference index with different values of wigwag angle in a rectangular field. (D) Wall-preference index with different values of wigwag angle in a circular field. (E) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a rectangular field. Wigwag angle was generated by a random number generator whose probability density followed a normal distribution of 0 and standard deviation of 0.3 rad. (F) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a circular field. (G) Wall-preference index with different values of wigwag interval in a rectangular field. (H) Wall-preference index with different values of wigwag interval in a circular field. ***, p < 0.001; **, p < 0.01; ns, not significant in Student's t-test. Numbers in bold type indicate the value that was the same as the actual measured value.
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pone.0142214.g005: Computer simulation of planarian spontaneous wigwag behavior.(A) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a rectangular field. Wigwag interval was generated by a random number generator whose probability density followed a log normal distribution with log mean of 0.14 sec and log standard deviation of 0.48. (B) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a circular field. (C) Wall-preference index with different values of wigwag angle in a rectangular field. (D) Wall-preference index with different values of wigwag angle in a circular field. (E) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a rectangular field. Wigwag angle was generated by a random number generator whose probability density followed a normal distribution of 0 and standard deviation of 0.3 rad. (F) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a circular field. (G) Wall-preference index with different values of wigwag interval in a rectangular field. (H) Wall-preference index with different values of wigwag interval in a circular field. ***, p < 0.001; **, p < 0.01; ns, not significant in Student's t-test. Numbers in bold type indicate the value that was the same as the actual measured value.

Mentions: When we tested planarian behavior with different wigwag angles by computer simulation, the results clearly showed a significant wall preference at smaller wigwag angles in both the rectangular model and circular model, whereas larger wigwag angles resulted in loss of the wall preference in both the rectangular model and the circular model (Fig 5A and 5B). The wall-preference index of the simulation clearly indicated that our model with 0.1–0.3 rad (5.7–17.2°) as SD of the wigwag angle was consistent with the actual wall-preference behavior (Figs 1, 4B, 5C and 5D). When we simulated the behavior with different wigwag intervals, the results showed that a longer interval caused strong wall preference in both the rectangular model and circular model (Fig 5E and 5F). The wall-preference index of the simulation clearly indicated that our model with wigwag interval SD of 0.1–1.0 sec was consistent with the actual wall-preference behavior (Figs 1, 4C, 5G and 5H).


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

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

Computer simulation of planarian spontaneous wigwag behavior.(A) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a rectangular field. Wigwag interval was generated by a random number generator whose probability density followed a log normal distribution with log mean of 0.14 sec and log standard deviation of 0.48. (B) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a circular field. (C) Wall-preference index with different values of wigwag angle in a rectangular field. (D) Wall-preference index with different values of wigwag angle in a circular field. (E) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a rectangular field. Wigwag angle was generated by a random number generator whose probability density followed a normal distribution of 0 and standard deviation of 0.3 rad. (F) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a circular field. (G) Wall-preference index with different values of wigwag interval in a rectangular field. (H) Wall-preference index with different values of wigwag interval in a circular field. ***, p < 0.001; **, p < 0.01; ns, not significant in Student's t-test. Numbers in bold type indicate the value that was the same as the actual measured value.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4635015&req=5

pone.0142214.g005: Computer simulation of planarian spontaneous wigwag behavior.(A) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a rectangular field. Wigwag interval was generated by a random number generator whose probability density followed a log normal distribution with log mean of 0.14 sec and log standard deviation of 0.48. (B) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag angle in a circular field. (C) Wall-preference index with different values of wigwag angle in a rectangular field. (D) Wall-preference index with different values of wigwag angle in a circular field. (E) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a rectangular field. Wigwag angle was generated by a random number generator whose probability density followed a normal distribution of 0 and standard deviation of 0.3 rad. (F) Trajectories (top) and heat map (bottom) of the simulated planarian behavior with different values of wigwag interval in a circular field. (G) Wall-preference index with different values of wigwag interval in a rectangular field. (H) Wall-preference index with different values of wigwag interval in a circular field. ***, p < 0.001; **, p < 0.01; ns, not significant in Student's t-test. Numbers in bold type indicate the value that was the same as the actual measured value.
Mentions: When we tested planarian behavior with different wigwag angles by computer simulation, the results clearly showed a significant wall preference at smaller wigwag angles in both the rectangular model and circular model, whereas larger wigwag angles resulted in loss of the wall preference in both the rectangular model and the circular model (Fig 5A and 5B). The wall-preference index of the simulation clearly indicated that our model with 0.1–0.3 rad (5.7–17.2°) as SD of the wigwag angle was consistent with the actual wall-preference behavior (Figs 1, 4B, 5C and 5D). When we simulated the behavior with different wigwag intervals, the results showed that a longer interval caused strong wall preference in both the rectangular model and circular model (Fig 5E and 5F). The wall-preference index of the simulation clearly indicated that our model with wigwag interval SD of 0.1–1.0 sec was consistent with the actual wall-preference behavior (Figs 1, 4C, 5G and 5H).

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