Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Crabs switch skeleton types


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

Note: Contact Taylor and Kier at 919-962-5017 or

David Williamson | EurekAlert!
Further information:

More articles from Life Sciences:

nachricht Novel mechanisms of action discovered for the skin cancer medication Imiquimod
21.10.2016 | Technische Universität München

nachricht Second research flight into zero gravity
21.10.2016 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>