A new study out of Sweden’s Lund University provides new information on how sea urchins “see” despite having no eyes. According to this study, these fascinating creatures use their feet to detect potential threats in their environment.
As they observed sea urchins in a variety of tests, biologists discovered a special group of cells in the animal’s tentacle-like feet. These cells can sense light, which helps urchins tell what objects are in their immediate vicinity.
To test just how good urchins’ sight is, researchers put the creatures in a cylindrical container with a light shining above them and shadowy areas in the corners. Investigators simulated an approaching predator by creating shadows above the sea urchins. While simulating these predators, scientists used electron microscopy tests and x-ray tomography to analyze the urchins’ vision.
In their report, study authors wrote that a predator had to take up between 30 to 70 degrees of the urchins’ 360-degree vision for the creatures to move towards the darkness. This is quite astonishing considering humans only need 0.02 degrees to spot a potential threat.
Dr. John D. Kirwan, who works at Lund University’s Department of Biology, was a lead author on this study. Other eminent professors involved in this research include Drs. Michael J. Bok, Jochen Smolka, James J. Foster, José Carlos Hernández, and Dan-Eric Nilsson.
Anyone interested in this study can find out more about this research in the latest edition of the Journal of Experimental Biology. This study was published under the title, “The sea urchin Diadema africanum uses low resolution vision to find shelter and deter enemies.”