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Extraocular Vision

  • 04 Jan 2020
  • 2 min read

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For the first time, researchers have shown that a species of brittle stars can see even though it does not have eyes.

  • The ability to see without eyes is known as extraocular vision.
  • The red brittle star (Ophiocoma wendtii) has become only the second creature, after a sea urchin species, known to have the extraocular vision (barring rare cases in other species).
  • In sea urchins and brittle stars, researchers suspect that extraocular vision is facilitated by the photoreceptor cells found on their bodies.
  • The researchers suggest that a brittle star sees with the help of light-sensing cells that cover its entire body. These light-sensing cells give the brittle star visual stimuli, allowing it to recognise coarse structures such as rocks.
  • Another peculiar feature of the red brittle star is its signature colour change. While the creature is deep red during the day, it changes its colour to beige at night.
  • The researchers think that there may be a link between their extraocular vision and colour changing abilities since the responses they saw in the creatures tested during the day, disappeared in those that were tested at night.

Source: IE

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