There are many cases where one experiment attempting to make one conclusion merely results in finding an entirely different one. The case of tagging starfish is one.
The experiment was pretty straight-forward:
At the University of Southern Denmark, students Frederik Ekholm Gaardsted Christensen and Trine Bottos Olsen were asked to tag some starfish. The task was simple: inject the Asterias rubens with microchips, the same kind that veterinarians implant in pet dogs. This would let researchers easily identify individual starfish later on. The technique had already been used successfully in sea urchins.
Simple enough. But when the researchers discovered all the tags that were once embedded deep inside the starfish’s bodies at the bottom of their tank, questions began to arise as to how the starfish were getting rid of the foreign objects.
To figure it out, the team injected the starfish with magnets and used an outside magnet to locate the position of the internal magnets. By tracking the magnet’s movements inside the animal, they discovered that while the magnets always exited the body at the end of an arm, they seemed to travel randomly throughout the body before exiting an arm. They also noted that the the starfish moved the foreign object by constricting themselves next to the magnet, causing it to slowly travel, something akin to how our body removes splinters from our fingertips, but on a much larger scale.
The next question to this strange superpower is why?
It’s already known that starfish have the ability to regrow an entire arm when one is lost. The scientist’s guess that in the process of regrowing a limb, small stones, rocks, or shells can become lodged in the body, and must be removed for proper use of the limb.
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