How many Eyes do Box Jellyfish have

Have you ever wondered How many Eyes do Box Jellyfish have? The number of eyes of Box Jellyfish are really going to astonish you. Make a wild guess as to how many eyes does it have. The visual system of the box jellyfish have been of particular interest for scientist and researchers. We have gathered some really interesting information about the eyes of jelly fish so continue reading and see whether your wild guess is correct or not.

How many Eyes do Box Jellyfish have

24 Eyes

  • Yes you read it right, Box jellyfish have 24 eyes that can be divided into four different types.
  • Only two of the eyes are similar to the eyes of vertebrates (like our eyes) and have the capability to form images. These are identified as upper and lower lens eyes
  • The remaining eyes are primitive in nature.
  • These eyes help the box jellyfish in doing complex task such as navigation, avoiding obstacles, fast directional swimming and responding to light.

How many Eyes do Box Jellyfish have

Structure of Eyes

  • Unlike other jellyfish, box jellyfish possess four true eyes that consists of retinas, corneas and lenses, and  twenty ocelli (simple eyes) that do not contain the retinas, corneas and lenses.
  • The structures that contains the eyes consists of transparent tissue within which the eyes are suspended. These eyes can rotate in any direction allowing the jellyfish to always orient their eyes upwards so that whatever the position of the jellyfish body is, its eyes must be looking upwards.
  • The visual field of the upper lens eyes is vertically centered, forming an angle that enable them to see the terrestrial world above them. Lights get refracted in water at 97 degrees and the visual field of the box jellyfish is in between 95 and 100 degrees.
  • The visual processing and integration happens partly within the rhopalia of box jellyfish.
How many Eyes do Box Jellyfish have
(A) Photograph of Tripedalia cystophora. There are four rhopalia located on the sides of the bell (arrow), which alternate with the four groups of tentacles at the corners. The lens eyes point inward, toward the center of the bell. Scale bar, 1 cm. (B) A photograph of a single rhopalium inside the rhopalial niche. Arrows indicate a pit eye and a slit eye. The slit and pit eyes are both identically matched on the other side of the rhopalium. (C) A photograph of an isolated rhopalium. Arrows indicate the upper and lower lens eyes. Scale bar, 200 μm.
Source: http://jeb.biologists.org/content/209/19/3758

Function of Eyes

  • The eyes of Box Jellyfish can be divided into two broad categories as per their functions.
  • The first category includes the complete eyes that are capable to form images and actually enable the box jellyfish to see specific light points. They are four in number.
  • Box Jellyfish can detect its habitat using these proper eyes from a distance of 10 meters (32.8 feet).
  • Beside the eyes that can form images, box jellyfish has twenty ocelli or simple eyes that are only capable to distinguish between darkness and light.
  • So, how do the jellyfish stay in the right place? They use their “upper lens eyes,” four eyes which can see through the water’s surface and into the space above. These eyes allow them to spot the mangrove canopy at distances of at least eight meters, and navigate towards them.

How many Eyes do Box Jellyfish have

Box Jellyfish Eyes Research

  • Recent research has shown evidence that even though Box jellyfish does not have a conventional brain yet its behavior is sophisticated. It uses one of its upward looking set of eyes to navigate towards it home and keeping itself close to it.
  • This visual navigation towards its home is not a simple behavior and this provides evidence that similar simple species are being underestimated due to lack of proper brain structure.
  • Another research study conducted on of the box jellyfish species showed that the upper lens eyes kept the jellyfish near to its habitat which was the roots of mangrove trees.
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