A team of researchers from the
University of Copenhagen and the Greenland Institute of Natural Resources has
found that starfish living in the dark on the ocean floor have eyes on their
arms that are similar to other starfish living near shore. In their paper
published in Proceedings of the Royal Society B, the group describes their
study of the unique sea creatures and what they learned about starfish vision.
Scientists have known for some
time that some starfish that live near shore have compound eyes in the tips of
their arms. In this new study, the researchers have found the same to be true
for many types of starfish that live in the dark at the bottom of the ocean.
To learn more about starfish
vision in places besides the shoreline, the researchers collected hundreds of
specimens (representing 13 species) from depths ranging from shallow waters to
1,000 meters below the surface—all living in the North Atlantic near Greenland.
They found that 12 of the species had compound eyes similar to those found in
starfish near the shoreline—the one lone species without eyes was a burrowing
starfish that lives relatively close to shore.
In all of those with compound eyes, the
eyes were uncovered, the researchers report, and were located on the bottom
side of the arm tip, which means the starfish bend the tips to use them,
pointing the eyes at targets. Visual acuity and sensitivity to light varied
among the species they studied.
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