Prawns, like many other arthropods (insects, spiders), have a unique type of vision called mosaic vision. Unlike our eyes that have a single lens to form a complete image, prawn eyes are compound eyes made up of hundreds or even thousands of tiny individual units called ommatidia.
Each ommatidia functions like a miniature pixel in a camera, detecting light and sending signals to the prawn's brain. The brain then assembles these individual points of light into a complete image, not unlike a mosaic artwork.
[Image of Prawn compound eye]
This mosaic vision has some advantages and disadvantages compared to our own sight.
Advantages:
Wider field of view:
Prawn's compound eyes offer a nearly 360-degree panoramic view of their surroundings, giving them excellent peripheral vision. This is helpful for detecting predators or prey from almost any direction.
Motion detection:
Mosaic vision is very good at detecting movement. As an object moves across the prawn's field of view, it stimulates different ommatidia in sequence, creating a clear impression of motion.
Disadvantages:
Lower resolution:
Since each ommatidia only provides a small piece of information, the overall image resolution is lower compared to our eyes. Prawns cannot see fine details or sharp images.
Limited color vision:
Most prawn species have limited color vision, typically only distinguishing between blue and green wavelengths.
Despite these limitations, mosaic vision is a well-adapted system for prawns and many other arthropods, allowing them to navigate their environment effectively.