Decentralized Control Mechanism for Determination of Moving Direction in Brittle Stars With Penta-Radially Symmetric Body

Kano, Takeshi; Kanauchi, Daichi; Aonuma, Hitoshi; Clark, Elizabeth G.; Ishiguro, Akio

doi:10.3389/fnbot.2019.00066

Cited by 4 publications

(7 citation statements)

References 14 publications

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“…Astley [12] described their turning behaviour in a short-term series, which was performed by changing the roles of arms rather than by rotating their body axis. Regarding escape situations, studies have reported that brittle stars avoid open or bright spaces [19,33], predator extracts [32] and KCl solution [10,11]. However, few studies have focused on how each arm reacts to such repellents and defines the direction of the movement of an individual.…”

Section: Deciding Moving Directionmentioning

confidence: 99%

“…Kano et al [11] proposed a model in which arm movements become potentially symmetrical to aversive stimulation. We initially expected such a symmetrical scheme to allow the animal to escape opposite to the stimulus.…”

Section: Deciding Moving Directionmentioning

confidence: 99%

“…Similar to typical echinoderms that show pentaradial symmetry, most ophiuroid species have five multi-jointed appendages called 'arms', which extend from the 'disc' at the centre of the animal. Previous studies have described arm movements in the locomotion of five-armed species in qualitative terms [4][5][6][7][8][9][10][11] as well as in quantitative terms [12,13]. Several locomotion modes have been known to occur even in a single species.…”

Section: Introductionmentioning

confidence: 99%

“…Some behavioural studies have supported the essential role of the nerve ring in locomotion. For instance, menthol-anaesthetic experiments described the nerve ring's function in initiating locomotion [19], whereas nerve cut experiments demonstrated its role in arm coordination [8][9][10][11]20,21].…”

Section: Introductionmentioning

confidence: 99%

“…Our primary hypothesis was that brittle stars would have a decentralized nervous system, as suggested by previous studies. Matsuzaka et al [19], for instance, observed that unanaesthetized arms carried food to the mouth in the wholly anaesthetized disc; Kano et al [11] cut the nerve ring at two points and observed that two-and three-armed portions within the five-armed body often crept oppositely to each other. To allow the variability of the total number of arms, each functional unit would neurally affect only the nearestneighbour units while ignoring distant ones.…”

Section: Introductionmentioning

confidence: 99%

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A general model of locomotion of brittle stars with a variable number of arms

Wakita

Kagaya

Aonuma

2020

J. R. Soc. Interface.

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Typical brittle stars have five radially symmetrical arms that coordinate to move the body in a certain direction. However, some species have a variable number of arms, which is a unique trait since intact animals normally have a fixed number of limbs. How does a single species manage different numbers of appendages for adaptive locomotion? We herein describe locomotion in Ophiactis brachyaspis with four, five, six and seven arms to propose a common rule for the movement of brittle stars with different numbers of arms. For this, we mechanically stimulated one arm of individuals to analyse escape direction and arm movement. By gathering quantitative indices and employing Bayesian statistical modelling, we noted a pattern: regardless of the total number of arms, an anterior position emerges at one of the second neighbouring arms to a mechanically stimulated arm, while arms adjacent to the anterior one synchronously work as left and right rowers. We propose a model in which an afferent signal runs clockwise or anticlockwise along the nerve ring while linearly counting how many arms it passes through. With this model, the question on how ‘left and right’ emerges in a radially symmetrical body via a decentralized system is answered.

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Section: Deciding Moving Directionmentioning

confidence: 99%

Section: Deciding Moving Directionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A general model of locomotion of brittle stars with a variable number of arms

Wakita

Kagaya

Aonuma

2020

J. R. Soc. Interface.

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Sea star inspired crawling and bouncing

Heydari

Johnson

Ellers

et al. 2020

J. R. Soc. Interface.

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The oral surface of sea stars is lined with arrays of tube feet that enable them to achieve highly controlled locomotion on various terrains. The activity of the tube feet is orchestrated by a nervous system that is distributed throughout the body without a central brain. How such a distributed nervous system produces a coordinated locomotion is yet to be understood. We develop mathematical models of the biomechanics of the tube feet and the sea star body. In the model, the feet are coupled mechanically through their structural connection to a rigid body. We formulate hierarchical control laws that capture salient features of the sea star nervous system. Namely, at the tube foot level, the power and recovery strokes follow a state-dependent feedback controller. At the system level, a directionality command is communicated through the nervous system to all tube feet. We study the locomotion gaits afforded by this hierarchical control model. We find that these minimally coupled tube feet coordinate to generate robust forward locomotion, reminiscent of the crawling motion of sea stars, on various terrains and for heterogeneous tube feet parameters and initial conditions. Our model also predicts a transition from crawling to bouncing consistently with recent experiments. We conclude by commenting on the implications of these findings for understanding the neuromechanics of sea stars and their potential application to autonomous robotic systems.

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A methodological exploration to study 2D arm kinematics in Ophiuroidea (Echinodermata)

et al. 2023

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Brittle stars, unlike most other echinoderms, do not use their small tube feet for locomotion but instead use their flexible arms to produce a rowing or reverse rowing movement. They are among the fastest-moving echinoderms with the ability of complex locomotory behaviors. Considering the high species diversity and variability in morphotypes, a proper understanding of intra- and interspecies variation in arm flexibility and movement is lacking. This study focuses on the exploration of the methods to investigate the variability in brittle star locomotion and individual arm use. We performed a two-dimensional (2D) image processing on horizontal movement only. The result indicated that sinuosity, disc displacement and arm angle are important parameters to interpret ophiuroid locomotion. A dedicated Python script to calculate the studied movement parameters and visualize the results applicable to all 5-armed brittle stars was developed. These results can serve as the basis for further research in robotics inspired by brittle star locomotion.

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Decentralized Control Mechanism for Determination of Moving Direction in Brittle Stars With Penta-Radially Symmetric Body

Cited by 4 publications

References 14 publications

A general model of locomotion of brittle stars with a variable number of arms

A general model of locomotion of brittle stars with a variable number of arms

Sea star inspired crawling and bouncing

A methodological exploration to study 2D arm kinematics in Ophiuroidea (Echinodermata)

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