Prehistoric animal lensesAn ancient tower-eyed trilobite had dozens of calcite lenses. Calcite is a crystal, which in its optically transparent form, is present in many animal eye lenses, the trilobite being the most studied animal. The calcite eye for early trilobites was an array of tightly packed, hexagonal facets (lenses) and the array was similar in structure and appearance to insect eyes of today. (Thank goodness humans are not formed this way or lensesinglasses.co.uk would be working all hours!)
Some species of dragonfly have more than 28,000 lenses per compound eye, a greater number than any other living creature. Imagine the sight test and glasses for those eyes!
With the eyes covering almost their entire head, they have nearly 360-degree vision. I imagine some of us would wish for this!
Chameleons have some of the strangest eyes on the planet, as they are able to move independently of each other. This results in almost 360-degree vision. The reptile can also switch between monocular vision – when both eyes are used separately – and binocular vision when both eyes are used to look at the same scene. Making lenses for this beast would challenge us at lensesinglasses but I am sure our skilled technicians would find a way.
Mantis shrimps (Stomatopoda)
Mantis shrimps probably have the most sophisticated vision in the animal kingdom. Their compound eyes move independently and they have 12 to 16 visual pigments compared to our three.
They are the only animals known to be able to see circular polarised light. Experiments suggest they may use this to send messages to each other – for instance, ‘this burrow is occupied’.
Bacteria aren’t actually animals – they’re single-celled microbes. But they deserve a mention because they are probably the world’s smallest and oldest example of a camera-type eye. Camera-type eyes use a single lens to focus light onto a sensitive membrane or retina.
Recent research has shown that the tiny cells of some cyanobacteria (bacteria that get their energy from sunlight) act as a lens. Their spherical body bends incoming light rays, focusing them on the opposite surface. Their entire body effectively becomes an eyeball. We could provide a wide range of lenses to protect that big eyeball!
A bacterial cell can sense the direction the light is coming from, and move towards it.
The critter with the world’s best colour vision (as far as we know) is the bluebottle butterfly. Where we have three different types of cones to detect colour, they have a whopping fifteen, some of which see in the UV spectrum
Whales have special hydraulics in their eyes that let them move their lenses nearer or farther from their retinas. This unique system allows the whales to see well both in and out of the water, and to compensate for the increased pressure they experience when they dive.
Prey animals, like deer, horses, and elk, who spend their time grazing out in the open and must be constantly on alert, have wide and narrow horizontal pupils, which gives them a wider field of vision than nearly any other animal. When they lower their heads, their eyes also rotate so they have a constant view of the area around them.