Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

5-limbed brittle stars move bilaterally, like people

10.05.2012
Brainless organisms choose a central arm and head that way

It appears that the brittle star, the humble, five-limbed dragnet of the seabed, moves very similarly to us.


The brittle star doesn’t turn as most animals do. It simply designates another of its five limbs as its new front and continues moving forward. Credit: Henry Astley/Brown University

In a series of first-time experiments, Brown University evolutionary biologist Henry Astley discovered that brittle stars, despite having no brain, move in a very coordinated fashion, choosing a central arm to chart direction and then designating other limbs to propel it along. Yet when the brittle star wants to change direction, it designates a new front, meaning that it chooses a new center arm and two other limbs to move. Brittle stars have come up with a mechanism to choose any of its five limbs to be central control, each capable of determining direction or pitching in to help it move.

The findings are published in the Journal of Experimental Biology.

Many animals, including humans, are bilaterally symmetrical — they can be divided into matching halves by drawing a line down the center. In contrast, brittle stars are pentaradially symmetrical: There are five different ways to carve them into matching halves. Whereas bilateral symmetrical organisms have perfected locomotion by designating a "head" that charts direction and then commands other body parts to follow suit, radial symmetrical animals have no such central directional control.

"What brittle stars have done is throw a wrench into the works," Astley said. "Even though their bodies are radially symmetrical, they can define a front and basically behave as if they're bilaterally symmetrical and reap the advantages of bilateral symmetry."

"For an animal that doesn't have a central brain, they're pretty remarkable," said Astley, the sole author of the paper.

Astley decided to study brittle stars after noticing that their appendages acted much like a snake's body, capable of coiling and unfurling from about any angle. Yet when watched brittle stars move about, he couldn't figure out how the individual arms were coordinating. "It was too confusing," said the fourth-year graduate student in the Department of Ecology and Evolutionary Biology. "There's no obvious front. There are five arms that are all moving, and I'm trying to keep track of all five while the (central body) disc was moving."

He decided to take a closer look, which, surprisingly, no other scientist had done. On a trip to Belize in January 2009 led by professor and department chair Mark Bertness, Astley plopped thick-spined brittle stars (Ophiocoma echinata) into an inflatable pool and filmed them. The animals were willing subjects. "They hate being exposed," Astley said, "so we put them in the middle of this sandy area and they'd move."

To move, brittle stars usually designate one arm as the front, depending on which direction it seeks to go. An arm on either side of the central arm then begins a rowing motion, much like a sea turtle, Astley said. The entire sequence of movement takes about two seconds. "They're pretty slow in general," Astley said.

To turn, the brittle star chooses a new center arm and the accompanying rowing arms to move it along. "If we as animals need to turn, we need to not only change the direction of movement, but we have to rotate our bodies," Astley explained. "With these guys, it's like, 'Now, that's the front. I don't have to rotate my body disk.'"

Oddly, the brittle star also chooses another type of locomotion — that to bilaterals would appear to be moving backward — about a quarter of the time, Astley documented. In this motion, the animal keeps the same front, but now designates the non-forward-rowing motion limbs to move it. The question, then, is why doesn't the brittle star define a new front and simply move forward? "There's clearly something that determines that," Astley said. "It could be the relative stimulus strength on the arms."

The research was funded by the private Bushnell Foundation.

David Orenstein | EurekAlert!
Further information:
http://www.brown.edu

More articles from Life Sciences:

nachricht Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>