A pair of biology students at the University of Southern Denmark (SDU) has discovered how starfish are able to squeeze out foreign objects from their bodies. The new discovery could hold the key to understanding how animals are able to heal themselves quickly.

SDU researchers Trine Bottos Olsen and Frederik Ekholm Gaardsted Christensen made the discovery almost by accident as they were working on their studies. The two students were asked to place tags in several starfish to allow scientists to identify the creatures again later.

However, when Olsen and Christensen placed the identifiers on the starfish, the tags did not stay inside the sea creatures.

"Every time we put a tag into a starfish, they rid themselves of the tag within a few days," the researchers explained.

"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."

Several members of the animal world are known to reject foreign objects from their bodies, similar to how a splinter could be pushed out from a person's finger merely by the movement of its body.

If the foreign object, however, is stuck deep inside the animal's body, such as when a bullet becomes lodged between several internal organs, it would make it difficult for the creature to remove it without the help of surgery.

Regarding the starfish in the study, the sea creatures did not attempt to get rid of the tags by simply pushing them back out of the area where they were injected. They instead allowed the foreign objects to travel through their bodies until they reached the tip of their arms. The creatures then removed the tags through an opening in that area.

The study shows the differences between the physiology of the human body and that of the starfish. The sea creatures are known to have an exoskeleton and also a nervous system that is decentralized. Their eyes are also located on the tips of each of their arms.

Similar to humans, starfish also have a body cavity that is filled with various internal organs. The tags the researchers placed inside the creatures were coursed through their body cavity until they were subsequently ejected through the tip of their arms.

While previous research have suggested how starfish are able to regrow whole organs and appendages, the SDU study is the first of its kind to show how creatures can remove foreign objects from their body.

The study is published in the journal The Biological Bulletin.