London, June 17 (IANS): Giving fresh insights into how certain animals can quickly heal themselves, a study reveals that starfish are able to squeeze foreign bodies along the length of their body cavities and out through their arm tips.

The two biology students from University of Southern Denmark have found a strange behaviour in starfish that was never before been observed.

Previous research found that starfish are able to regenerate whole limbs and organs.

They were asked to tag some starfish (Asterias rubens), so that researchers could reidentify and study the starfish.

The tags were injected into the starfish like a veterinarian tags a dog or cat.

"Every time we put a tag into a starfish, they rid themselves of the tag within a few days. It came out directly through the skin; the starfish simply pushed it out through the skin at the end of one arm and then went on as if nothing had happened," said Frederik Ekholm Gaardsted Christensen and Trine Bottos Olsen, biology students from University of Southern Denmark.

The starfish do not attempt to push the tag out of the hole in the skin through which it was injected.

In fact, they let the tag wander randomly between the organs for a while, before they finally squeezed it out through an arm tip.

Starfish have an external skeleton and decentralised nervous system, and their eyes are placed on the end of each arm.

But they have a body cavity filled with organs, and it is through the body cavity that the tag moves before it reaches the tip of an arm.

The results were outlined in the journal Biological Bulletin.