Crocodiles' Super-skin Can Detect Environmental Changes

Crocodiles, alligators and their kin have sensory organs in their skin that are sensitive to heat, cold, touch and the chemicals in their environment, researchers report. These sensors, micro-organs known as integumentary sensory organs (ISOs), are reportedly unique to the crocodilian order.

"ISO sensors are remarkable because not only are they able to detect many different types of physical and chemical stimuli, but because there is no equivalent in any other vertebrates," said lead researcher Michel Milinkovitch of the University of Geneva.

"It is this transformation of a diffuse sensory system, such as we have in our own skin, into ISO which has allowed crocodilians to evolve a highly armored yet very sensitive skin."

Crocodilians, a group that includes crocodiles, alligators, caimans and gharials, have tough, scaly skin with boney plates for added protection. The ISOs, which are a sensitive as fingertips, are found on the heads of crocodilians.

Nile crocodiles (Crocodylus niloticus) and the spectacled caiman (Caiman crocodilus) were studied in an investigation of the ISOs. Researchers found that the ISOs start to develop while the creatures are still embryos before scales begin to form on their skin. The Nile crocodiles were particular in their development of ISOs, which are found not only on their heads but all over their body.

The extreme sensitivity of the ISOs allows the animals to detect surface pressure waves in the water, allowing them to locate prey even in the dark. The thermal sensitivity allowed by the ISOs helps crocodilians maintain the right body temperature by moving between warm and cool areas. Researchers reports the ISOs' ability to detect chemicals may even be employed in helping the animals choose suitable habitats

Milinkovitch and his colleagues' research is published in the open access journal EvoDevo.