Crocodiles and alligators are notorious for their well-armoured bodies. So it comes as something of a surprise to learn that their sense of touch is one of the most acute in the animal kingdom. Their sense of touch is concentrated in a series of small, pigmented domes that dot their skin all over their body.
A new study, published in the Journal of Experimental Biology, has discovered that these spots contain a concentrated collection of touch sensors that make them even more sensitive to pressure and vibration than human fingertips.
"We didn't except these spots to be so sensitive because the animals are so heavily armoured," said Duncan Leitch, the gratude student who performed the studies under the supervision of Ken Catania at Vanderbilt University.
Scientists who have studied crocodiles and alligators have taken note of these spots, which they have labeled "integumentary sensor organs" or ISOs. As a result, Leitch began a detailed investigation of the ISOs and their neural connections in both American alligators and Nile crocodiles. Leitch found that these sensory spots are connected to the brain through the trigeminal ganglia, the nerve bundle that provides sensation to the face and jaw in humans.
In addition, his studies ruled outmost of the alternative hypothesis for the ISOs function. What he did find is a diverse collection of "mechanoreceptors:" nerves that respond to pressure and vibration. Some are specially tuned to vibrations in the 20-35 Hertz range, just right for detecting tiny water ripples. Others respond to levels of pressure that are too faint for the human fingertip to detect.
Their analysis led the scientists to conclude that the crocodilian's touch system is exceptional, allowing them to not only detect water movements created by swimming prey, but also to determine the location of prey through direct contact for a rapid and direct strike and to discriminate and manipulate objects in their jaws.
Their finding that the most heavily wired ISOs are located in the mouth near the teeth suggests that the touch sensors help the animals identify the objects that they catch in their jaws. The sensors also appear to provide the sensitivity that female alligators and crocodiles need to delicately break open their eggs when they are ready to hatch and to protect their hatchlings by carrying them in their jaws, the same jaws that can clamp down on prey with a force of more than 2,000 psi.
"We didn't except these spots to be so sensitive because the animals are so heavily armoured," said Duncan Leitch, the gratude student who performed the studies under the supervision of Ken Catania at Vanderbilt University.
Scientists who have studied crocodiles and alligators have taken note of these spots, which they have labeled "integumentary sensor organs" or ISOs. As a result, Leitch began a detailed investigation of the ISOs and their neural connections in both American alligators and Nile crocodiles. Leitch found that these sensory spots are connected to the brain through the trigeminal ganglia, the nerve bundle that provides sensation to the face and jaw in humans.
In addition, his studies ruled outmost of the alternative hypothesis for the ISOs function. What he did find is a diverse collection of "mechanoreceptors:" nerves that respond to pressure and vibration. Some are specially tuned to vibrations in the 20-35 Hertz range, just right for detecting tiny water ripples. Others respond to levels of pressure that are too faint for the human fingertip to detect.
Their analysis led the scientists to conclude that the crocodilian's touch system is exceptional, allowing them to not only detect water movements created by swimming prey, but also to determine the location of prey through direct contact for a rapid and direct strike and to discriminate and manipulate objects in their jaws.
Their finding that the most heavily wired ISOs are located in the mouth near the teeth suggests that the touch sensors help the animals identify the objects that they catch in their jaws. The sensors also appear to provide the sensitivity that female alligators and crocodiles need to delicately break open their eggs when they are ready to hatch and to protect their hatchlings by carrying them in their jaws, the same jaws that can clamp down on prey with a force of more than 2,000 psi.
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