The Mantis Shrimp
This is the mantis shrimp. This mantis shrimp can grow up to 7 inches long (~18cm) and mostly resides in the reefs of the Indian and Pacific oceans at depths of around 1500 meters. The mantis shrimp also have claws strong enough to stun prey up to 200lbs (91kg).
Despite having a claw force strong enough to break through the shell of crabs, this is not even close to their strongest attribute and the one that makes them so reputable in the animal kingdom. This attribute is their unique and advanced eyes and vision.
Colour Vision Of The Mantis Shrimp
The mantis shrimp has one of the most advanced levels of colour vision among all living organisms. The mantis shrimp perceives light of different colours between the wavelengths of 320-700 nm and are able to see the same colours humans can but with an increased depth and accuracy.
This visible light spectrum of theirs also allows them to see ultraviolet light. However, they are currently not believed to be able to perceive any form of infrared light.
In comparison to humans, we have a colour perception of light between the wavelengths 380-750 nm and can distinguish between around 10 million unique colours.
While the wavelength spectrums the mantis shrimp and humans can perceive is rather similar they have the added advantage of having plenty more different kinds of photoreceptors than we do.
The Photoreceptors In Mantis Shrimps’ Eyes
Photoreceptors are the cells in our eyes that respond to different wavelengths of light which allow us to see different colours. These cells are also known as cone cells.
Humans have 3 different photoreceptors, one for each individual colour our vision is based on. These colours are red, green and blue. This is what sets the mantis shrimp apart from humans because the mantis shrimp has up to 16 different ones.
However each different photoreceptor doesn’t add an extra base colour to their vision in the same way it does to ours. It more so adds depth to the colours we can see within our vision.
Despite their very advanced eyes and an incredible assortment of photoreceptors they still are not very good at actually distinguishing between them though.
The shrimp are able to differentiate between colours corresponding to wavelengths of around 25 nanometers apart. In comparison to humans, this is not very precise as we can detect differences around 1-4 nanometers.
To put this into a visual perspective the shrimp can detect differences in colour that for us is about the equivalent to the difference between darker greens and lighter blues.
Research has however shown that it also serves a purpose that we didn’t quite anticipate. The main example of this is the fact that their colour recognition is extremely advanced despite their differentiating abilities being rather weak.
This is because all the different types of photoreceptors in their eyes allow them to detect changes in their surroundings somewhat easily. This is because the extra photoreceptors make their eyes more sensitive to sudden changes instinctively.
Regarding their rather poor differentiating abilities between colours however it makes sense why they have evolved to be this way. This is because differentiating between small differences in different shades of colours doesn’t exactly serve a purpose to these creatures.
The main reason for this is the fact that at its preferred depth of living (1500 meters) most colours are not visible. This is because the mass amount of water the light has to go through simply blocks it out which makes it almost completely dark in these depths.
Mantis Shrimps Can See Polarized Light
The purpose of having this amount of photoreceptors is however even more remarkable than being able to simply see more colours. It allows them to see polarized light.
Polarized light is simply put light that only vibrates on one plane instead of in a 360-degree field as normal unpolarized light does.
Polarized light normally only occurs when light refracts, which is most commonly seen when light hits water. Even in this situation though the polarization is rather small and not normally noticeable by our naked eyes, however, this is something that the mantis shrimp is able to detect.
This is rather extraordinary considering that these shrimp are in fact the only animal recorded to this date to be able to see this sort of light without external aid. While we humans are able to see polarized light we need special glasses in order to do so in contrast to the natural capabilities the mantis shrimp has.
The Eye Structure Of Mantis Shrimps
The eye structure of the mantis shrimp is quite possibly the most fascinating thing about this creatures complex eye structure.
Much like insects and other crustaceans these shrimp have a form of compound eyes. This essentially means that it has several tiny “eyes“ called ommatidia that all work independently from each other but come together to form a vision for the creature.
The mantis shrimp has been found to have over 10 000 ommatidial in each eye. To put this into perspective a honeybee has around 150 in each eye whereas a fruit fly has 700.
Another interesting thing to note about their eye structure is the band that runs horizontally through them. This band consists of 6 individual strips of photoreceptors in a high concentration.
In addition to the already unique band that goes through their eye, this is also where their polarized light perception takes place, more specifically in their 5th and 6th row.
The Advantages Of Having Advanced Vision
There are many advantages of having an advanced vision, some of which we have figured out and others which we are yet to discover.
One advantage that their advanced vision gives them is the ability to spot predators with slightly shimmering scales such as barracudas. It can also help them spot prey on their own since they can be transparent and otherwise very hard to notice.
Another use that has been found for this vision is found within their mating periods. This is because they emit fluorescent light that matches the wavelengths that can be detected by their eyes while remaining undetectable by other creatures.
This allows them to stay hidden while also giving them ways to find each other in the dark parts of the ocean. This in turn increases their survival rates as it becomes increasingly harder for predators to find them when they don’t give off clear detectable signs of presence.
There are without a doubt more advantages of having a vision this advanced but this is about as far as it goes for the time being with the current research that has been conducted on these shrimp. We still have a lot to learn about their vision and how it is used to perceive the world in ways we don’t understand yet.
The animal with the most advanced vision is the mantis shrimp which has 16 different types of photoreceptors in its eyes, compared to our 3.
They are also able to detect polarized light. Polarized light is normally not detected by most eyes found in the animal kingdom, but mantis shrimps are able to detect it through their complex eyes.
It makes use of these abilities to stay vigilant and observant of its environment in the case of possible predators, which means they are normally able to spot the predator before the predator spots them.