Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tactile croc jaws more sensitive than human fingertips

08.11.2012
Armoured in elaborate scales, the skins of crocodiles and alligators are much prized by the fashion industry. But sadly, not all skins are from farmed animals.

Some are from endangered species and according to Ken Catania from Vanderbilt University, USA, sometimes the only way to distinguish legitimate hides from poached skins is to look at the distribution of thousands of microscopic pigmented bumps that pepper crocodiles' bodies.

Adding that the minute dome organs are restricted to the faces of alligators, Catania puzzled, 'What are the organs for?' Explaining that they have been proposed to detect subtle shifts in water salinity and shown to sense ripples in water, Catania says, 'We suspected that there might be more to the story', so he and Duncan Leitch teamed up to take a closer look at the small structures. The duo discovered that the bumps are tactile and even more touch sensitive than human fingertips. They publish their discovery in The Journal of Experimental Biology at http://jeb.biologists.org.

Observing the skin of American alligators and Nile crocodiles with scanning electron microscopy, Leitch could see that each dome was surrounded by a hinge depression. And when he sliced through a series of domes to identify the sensory receptor structures beneath, he found sensitive free nerve endings near the dome surface, and laminated corpuscle structures – which are vibration sensitive – and dermal Merkel complexes – which respond to sustained pressure – in the lowest skin layer.

Next, Leitch stained the nerve structures leading from the skin through the reptile's jaw and painstakingly traced the sensitive trigeminal nerve as it branched to the domes. 'The innervation of these jaws was incredible!' exclaims Catania. The entire jaw was infiltrated with a delicate network of nerves. 'There was a tremendous number of nerve endings and each of the nerve endings comes out of a hole in the skull', Leitch adds. Referring to the animal's combative lifestyle, he suggests that this arrangement protects the delicate trigeminal nerve fibres – carried inside the skull – from damage during attacks while maximising the nerve endings' sensitivity at the surface.

But none of these observations answered the question of which system the domes relay sensory information to. Recalling that the domes had been proposed to detect salinity changes and even electric fields, Leitch gently bathed the limbs of Nile crocodiles in brackish water while carefully recording the electrical activity in the spinal nerve, but couldn't detect a signal. And when he repeated the experiments while applying a weak electric field to the water, there was no response again. However, when Leitch gently touched one of the sensory domes with a minute hair designed to test human touch sensitivity, he discovered that the domes around the animals' teeth and jaws were even more touch sensitive than human finger-tips. And when he filmed crocodiles and alligators going about their business in the aquarium at night, he was impressed at how fast the animal's 50 ms response times were. 'As soon as they feel something touch, they snap at it', recalls Catania.

So, why do such well-armoured animals require such an exquisite sense of touch? Leitch suggests that this sensitivity allows the animals to distinguish rapidly between unpalatable pieces of debris and tasty prey while also allowing mother crocodiles to dextrously aid their hatching young by extracting them from the egg with their jaws. The pair is keen to understand how these sensory areas map onto the forebrain. Explaining that massive regions of the human brain are dedicated to processing touch sensory information, Catania says, 'Crocodilians are not an ancestor to humans, but they are an important branch that allows us to fill in key parts of the evolutionary puzzle for how sensory maps in the forebrain have evolved'.

IF REPORTING ON THIS STORY, PLEASE MENTION THE JOURNAL OF EXPERIMENTAL BIOLOGY AS THE SOURCE AND, IF REPORTING ONLINE, PLEASE CARRY A LINK TO: http://jeb.biologists.org/content/215/23/4217.abstract

REFERENCE: Leitch, D. B. and Catania, K. C. (2012). Structure, innervation and response properties of integumentary sensory organs in crocodilians. J. Exp. Biol. 215, 4217-4230.

This article is posted on this site to give advance access to other authorised media who may wish to report on this story. Full attribution is required, and if reporting online a link to jeb.biologists.com is also required. The story posted here is COPYRIGHTED. Therefore advance permission is required before any and every reproduction of each article in full. PLEASE CONTACT permissions@biologists.com

kathryn Knight | EurekAlert!
Further information:
http://www.biologists.com

More articles from Life Sciences:

nachricht Water world
20.11.2017 | Washington University in St. Louis

nachricht Carefully crafted light pulses control neuron activity
20.11.2017 | University of Illinois at Urbana-Champaign

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>