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 A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>