Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Crabs switch skeleton types

11.07.2003


Working with blue crabs, biologists at the University of North Carolina at Chapel Hill have discovered what may turn out to be a previously unrecognized, fundamental and widespread support mechanism in crabs, lobsters, insects and other arthropods that periodically shed their hard external skeletons.



Doctoral student Jennifer R.A. Taylor and William M. Kier, professor of biology, have found that rather than being flaccid and mostly immobile after molting, crabs switch to what’s called hydrostatic support. That very different "skeleton" allows the creatures to move around efficiently, hide and even defend themselves during the week or so it takes for their soft, newly grown shells to stiffen completely.

A report on the discovery appears as the cover story in the July 11 issue of the journal Science. To their knowledge, the work is the first to show animals switching back and forth between two different skeleton forms. "This is an exciting concept for us because it’s not something that we thought animals could do," Kier said. "Crabs certainly are more vulnerable without the tough body armor they grow to protect themselves, but they are not at all helpless. It turns out that they can run around, swim and exert considerable force."


When they need more room to grow, blue crabs swallow a lot of water to puff themselves up and then crack apart and discard their old shells. Within a day, their outer membrane, which is called the cuticle, begins to toughen and harden.

In experiments Taylor conducted under Kier’s supervision, the researchers found that internal pressures were temporarily far higher after molting than they were before. Those fluid forces can be controlled to move legs and claws almost as efficiently as when the interplay between muscles and the outer shells causes movement.

In a preliminary test to determine if hydrostatic pressure was necessary for newly molted crabs to maintain their shape and support, researchers made a small hole in a crab’s cuticle. Because it sealed the hole almost instantaneously, loss of fluid was minimal, Taylor said. After removing a larger part of an entire claw, however, the rest of the claw collapsed like a tire going flat.

Further experiments involving force and pressure sensors showed that when newly molted crabs tried to pull their claws in toward their bodies, their internal hydrostatic pressures shot up, she said. Still more measurements, taken as control experiments, showed that seven days after molting, internal pressures did not increase when the animals pulled in their claws.

"These data imply that hydrostatic support is no longer used once crabs have returned to the hard-shell condition," Taylor wrote. "Most arthropods grow by molting, and thus, many may undergo this change in skeletal support. It is clear that the shedding of the exoskeleton does not incapacitate a crustacean."

Some animals, such as worms and polyps, rely exclusively on hydrostatic support throughout their lives, Kier said. Others, such as mammals, chiefly employ a bony skeleton like humans do, but also usually require hydrostatic support to enable tongues to extend and penises to become erect. Other examples of animals’ supplementary use of such support are elephant trunks and clams’ soft, burrowing "foot" and siphons.

"This is also exciting to us since crustaceans belong to a really big group, the arthropods, which includes insects and are the most diversified non-microscopic animals on Earth," Kier said. "We haven’t looked for this switching back and forth of the skeleton in insects yet, but we will. There is a good chance that we will find it."



The National Science Foundation and the National Aeronautics and Space Administration (NASA) supported the UNC College of Arts and Sciences studies.

By David Williamson
UNC News Services
919-962-8596

Note: Contact Taylor and Kier at 919-962-5017 or billkier@bio.unc.edu

David Williamson | EurekAlert!
Further information:
http://www.unc.edu/

More articles from Life Sciences:

nachricht Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

17.01.2017 | Materials Sciences

Smart homes will “LISTEN” to your voice

17.01.2017 | Architecture and Construction

VideoLinks
B2B-VideoLinks
More VideoLinks >>>