A new type of eye has been discovered in a fish that dwells in the deepest parts of the ocean around Australia and New Zealand. The Glasshead Barreleye Fish lives in almost complete darkness, and therefore has to maximise the little light that can be detected.
The fish appears to have 2 sets of eyes, but in fact it is one pair that are split in two. The first set point upwards to see potential prey or predators that are silhouetted from light above. The second section of the eye has mirror like retinas that are capable of detecting bioluminescent flashes that are created by other deep sea creatures around them. These silvery looking eyes are able see both to the sides and below, giving the fish a full 360 degree field of vision! The reflector eyes have a conventional lens at the top, but have a curved mirror formed of guanine crystals which can reflect light onto a second retina.
Reflector eyes have previously been found in invertebrates such as crustaceans, but never previously in a fish. The broad field of vision created is a great advantage at depths, not only in helping to find food, and mates, but also in avoiding becoming prey themselves.
Many animals have developed extraordinary eyes in order to cope with challenging environments. The colossal squid also lives at extreme depths and has the largest eyes ever recorded, measuring in at about 30-40 centimetres, again presumably to capture as much light as possible. The chameleon can swivel its eyes independently, one used for watching for prey, the other for avoiding predators. Goats can see behind them! You can never surprise a goat.
Did you know that sharks eyes are the most similar to humans? Apart from being able to roll their eyes into the back of their heads to prevent them being damaged in attacks. Its a weird and wonderful world out there!