Starfish Navigate Using Primitive Eyes on Their Arms: Study

A study has discovered that starfish visually navigate the ocean floors using the primitive eyes present on the tip of their arms.

The study conducted by Dr.  Anders Garm at the Marine Biological Section of the University of Copenhagen in Denmark says that starfish have image-forming and could their study could provide a necessary link in eye evolution.

For the study, the researchers picked up starfish both with eyes and without and placed them a little afar from their natural habitat, the coral reef. They wanted to observe if the starfish would float back to the source of food or starve

From the surface the researchers carefully observed the behavior of the starfish and noticed that those starfish that had eyes intact moved toward the direction of the reef and those without eyes moved around aimlessly.

According to Dr. Garm, the results of this study highlight the fact that the starfish nervous system is able to process visual information, and also show that scientists had underestimated the ability of the dispersed nervous system of the echinoderms.

On examining the morphology of the photoreceptors in the eyes of the starfish are still primitive but have evolved a little.

Dr Garm said , "From an evolutionary point of view it is interesting because the morphology of the starfish eyes along with their optical quality (quality of the image) is close to the theoretical eye early in eye evolution when image formation first appeared. In this way it can help clarify what the first visual tasks were that drove this important step in eye evolution, namely navigation towards the preferred habitat using large stationary objects (here the reef)."