How Many Eyes Does a Tarantula Have / Science of Tarantula’s Vision
How Many Eyes Does a Tarantula Have. Since Tarantulas are crepuscular animals, they are best active at owl-light or twilight. Their vibrant colors are difficult to recognize. If we think about our own eyesight in the night, colors become indistinctive and we struggle to distinguish between two different colors.
But there are some animals example bats, moths, or geckoes which have good color vision even in almost total darkness. Scientists have discovered that Tarantulas have different kinds of ‘Opsin genes’ which produce opsin proteins. These proteins are present in photoreceptor cells in their eyes which help them see different hues. Though it is contradictory that they have a great diversity of these opsin genes and good color vision.
How Many Eyes Does a Tarantula Have / They Brilliant Colors?
Some scientists say that spiders with blue and green colors can protect themselves better than those without them. There are two colors- Green and Blue in the Tarantula color wheel which plays important role in their vision. How Many Eyes Does a Tarantula Have
They camouflage themselves using these colors to protect themselves from a predator. It is also said that these colors help make predators stay away. They rub their mouthparts along with making a noise called stridulation or shoot their hair as a protecting weapon which is called Urtication.
We don’t know if stridulation and urtication have a connection between them or with blue-green coloration but they help them avoid themselves being seen as called ‘crypsis’. Green coloration is probably due to their tree-dwelling behavior. Though the function of Blue color is not clear. All Tarantulas are carnivores and use their spinnerets to produce silk webs but they don’t make classic old webs to catch flies.
How Well Do Tarantulas See/ They Have Bad Eyesight
Tarantulas cannot see very well. They have very poor vision. Arboreal Tarantulas are better than the terrestrial ones in this matter. Terrestrial Tarantula can differentiate between day and night or light and dark only from a closer distance.
They just detect some motion happening around them. They can see the wavelength of 350 to 640 nm. For humans, it is 380-780 nm. They can’t see Red light as it is of wavelength 650-750 nm, so you can use camera flash with a red light to capture them. They use hair present on their legs and body to sense their surroundings.
They need to see to move, make their webs, and to sense potential prey or predator. There are some exceptions, the free-roaming spider has excellent eyesight which includes flower spiders, jumping spiders, and net casting spiders.
Why Do Tarantulas Have Eight Eyes?
We know spiders are famous for having eight legs little did we know they have eight eyes as well. Insects possess compound eyes having multiple lenses. Some spiders may have six eyes but Tarantulas generally have eight eyes- 2 large round eyes in the center and 3 eyes around them on each side. Primary eyes pointing forwards are immovable and functions to get a clear and colored image.
They also help them to judge distance. The secondary eyes present on their sides are movable and help to detect if something moves. Also, spiders do not possess neck hence they can’t turn their head to see the world around them. The extra eyes help them to easily spot the prey around them.
They are mainly hunters and use their eyes for sharp and colorful vision. The eyes just lateral to the central eyes are meant for some detailing. Having more eyes help determine which direction to move. It is seen that arachnids when moving lower the number of eyes.
What Colors Are Tarantulas Eyes?
Blue is the common color found in Tarantulas which is thought to be the ancestral color. The green color is also found in them but it is rare as compared to the blue color. The primary eyes are darker as compared to the secondary eyes which are lighter due to the presence of a light-reflecting crystal layer- the tapetum. This tapetum intensifies the image formation.
How Do Tarantulas Use Their Vision?
Unlike humans that have one pair of eyes. Tarantulas make use of their 8 eyes to detect motion and light-dark around them. The secondary eyes named Anterior lateral eyes, Posterior median eyes, and Posterior lateral eyes. The principal eyes are called the Anterior median eyes and are responsible for acute vision and identification of prey and predators.
The principal eye structure resembles a pair of binocular is black, first passes through two large cornea lenses that possess a combined field of view of roughly 90 degrees. A long narrow eye tube leads from the corneal lens to a small retina with a field of view of two to five degrees. The Retina has a second lens to increase the magnification of the image on the cornea lens. Six muscles attached to the tubes allow movement while the corneal lens remains fixed. This enhances the image and brings it into focus.
Unlike human eyes which have a single plain retina, a Tarantula’s retina is split into four layers distinguishing between blue, green, and ultraviolet which assists in effective color discrimination. Humans focus on an image by changing the shape of the lens however in spiders with a thin layer of Retina the receptors are assembled in a staircase positioning them at different distances from the lens.
This means that regardless of the distance the object of interest is, the eye tubes can sweep the staircase of the retina to cast an in-focus image. The image that spiders see is superimposed on the retina. They look like Boomerangs. But the retinas have a small field of vision. They mainly pick up fine detailing of the object, so they have to know where to look. That is the role of the most forward pair of small eyes.
They pick up motion and alert the primary eyes. Tarantulas require eyes because they are dependent on visual feedback to guide their behavior. Due to eyes being fixed, several eyes positioned around the head can detect movement causing them to turn their face towards the object of interest so they literally have eyes in the back of their head.
Even Though they have a large number of eyes but they mainly depend on vibration, touch, and taste stimuli to find and locate their prey. Some spiders can detect polarised light using median eyes which help them to locate properly in hunting. The lens present in Tarantulas is better than the photographic lens in terms of image brightness. But their retinas have course mosaics in the receptor cells which makes their image resolution poorer than humans.
Can Tarantulas See Infrared Light?
Differentiating between colors and light is dependent on the number of cone cells present in the eyes and their location in the retina. Humans can see many colors which animals cannot see but there are some colors or light that they can see but we cannot. Interesting!
Humans can see only the visible portion of light. There are some portions that are ultraviolet and infrared. Tarantulas and many other insects can see ultraviolet light that we humans can’t see but these Tarantulas are unable to detect infrared light which is detected well by snakes. They can see the wavelength of 350 to 640 nm. They can’t even see the red light and assume it is dark.
How Tarantula’s Eat?
Most people think it is all about fangs. You might think that Tarantula just pounces on its prey, sinks its fangs in it, and after injecting their venom in it starts eating them, while some of it can be true but the truth is a little bit more complicated. If you notice, you’ll see they actually don’t touch it with their fangs first but rather grabs its prey with their palps and forelegs before it sinks the fangs in.
They are careful creatures since they have delicate exoskeletons, soft abdomens that can be punctured easily so they have to be careful while approaching their prey. They sense everything happening around them using their hair.
Also, they also produce webs which they use to line their burrows or hides and lay down around them like tripwires to alert them when the prey has come close enough for them to venture out and pounce if vibrations are too strong as in a large predator coming around the Tarantula will usually scurry down into his burrow or hide and wait until the danger has passed.
Tarsal hooks present on their feet help them to sense if they want to eat and grab the prey. They pull their prey and envenomate them according to vibrations they sense. They release the digestive enzymes and liquefy them. Then they slurp the liquefied parts of their prey using a sucking stomach since they don’t have a mouth that can chew or masticate.
CONCLUSION
Vibration is everything to Tarantula. Neither do they smell, taste nor recognize their owners. They have no nervous system. They have poor vision. Hair or setae present on their body helps them sense their prey or anything happening around them.
