How many eyes does a spider have? Spider vision


Unlike the developed species of arthropods, the vision of arachnids is weak. Their eyes have a simple structure. There may be up to six pairs on their body, but this rather confirms the fact of their imperfect perception of the surrounding world. The answer to the question of how many eyes a scorpion cannot provide a clear understanding of the quality of its visual system. Therefore, it makes sense to figure out how he adapted to survive with such an imperfect “optics”.

Simple and complex vision of arthropods

Insect vision is most developed. In this regard, the arachnid eyes are often called simple. The developed representatives of insects - bees, dragonflies, flies and other similar - complex eyes have a faceted structure. The structural visual unit is ommatidia. Of them, in fact, consists of a complex optical system. Located nearby, they make up the visual complex. Ommatidium consists of a biconvex lens (cornea), under which there is a transparent cone, similar in properties to the lens.

Below is a layer of cells (retina) capable of perceiving light. They connect to the nerve endings that transmit signals to the brain. From each ommatidia information comes separately. As a result, the picture consists of many points and resembles a mosaic image.

In flies, the number of such structural elements reaches 4 thousand in each eye. In more developed in this regard, dragonflies and even more - up to 28 thousand. It is known that arachnids have several pairs of eyes. How many eyes of a scorpion have a complex structure? They do not have a complex visual system. It is represented by several separately located eyes, ommatidia. And one of their larger pair is considered the main one. The rest (up to 5 pairs) are located on the side and are considered auxiliary.

More simple lateral eyes (stems) are found in insect larvae. Moving to a higher stage of development, their visual system becomes more complicated. Another type of simplified eyes (dorsal) is not “reborn”, but remains at the same level in adults. Ommatidium does not form in them (there is no cone and lens). Under the cornea, light-receiving cells are located. Below that is the pigment layer connected to the nerve endings.

Scorpios: lifestyle

These arthropods are most commonly found in regions with a tropical climate. Some species are diurnal, but the overwhelming majority of them are still night hunters. They prefer to hide from the scorching heat and hide during this period under stones, snags and in other secluded places.

This is partly due to their imperfect vision. They can see the danger only at close range, and they can better hunt at night. But this is not only because of the specific features of vision. No matter how many eyes a scorpion has (picture below) - they do not play a decisive role in catching prey. It is believed that the main merit of accurate attacks - sensitive sensors on their feet.

The circular setting of the feet gives the scorpion the opportunity to feel the smallest vibrations of the soil from all sides. From the speed of propagation of such signals (the nearest paws are felt earlier), it determines the exact location of the victim. The eyes in this play a secondary role. It is noticed that if a scorpion and a victim are separated by a barrier in the form of a thin crevice, he will not be able to attack her even from close range. Signals on the soil from moving the prey to its sensitive legs in this case do not reach.

How many eyes have a scorpion

The habitat and features of life significantly changed the appearance of these creatures. It is not only the overall size of the body and its individual parts that differ, but also the number of eyes. Regardless of their total number, they all have a simple structure.

How many eyes of a scorpion, and where are they located on the body? Some species have adapted to live with one pair. The maximum number is 12 simple eyes. Moreover, one pair of them (obviously larger) is located in the center and plays the main role. The rest are located on the sides and lower around the perimeter.

Having caught the victim with its front claws, the scorpion raises it above its head and pierces with the tip of the sting that is at the end of the tail. How many scorpion eyes control this process? Presumably, the steam on top is to a certain extent just responsible for this. Whether simple additional eyes are a complication of the visual system (developed for improvement) or simplified (did not manage to completely atrophy), it is not possible to establish for certain.

Number of eyes in spiders

Zoo-ophthalmologists (specialists in the field of vision in animals), having heard the question of how many eyes a spider has, will not give a definite answer. The fact is that the number of eyes in spiders varies depending on the species.

But still it is known how many eyes in most species of spiders are four pairs. However, owners of 12 (!) Organs of vision are known. In the course of evolution, nature left spiders with as many organs of vision and precisely as much force as they needed for survival and reproduction. At the opposite poles, the cave spiders are located on the opposite poles — practically blind people — and racehorses whose visual power is equivalent to the human and yet they are able, as shown, to distinguish colors.

As a rule, located in two rows of eyes have different functionality. The so-called medial, she is the front pair, is called the main eyes. All other organs of vision are called secondary. Unlike insects with so-called faceted eyes, where certain parts of the eyes perform their characteristic functions, spiders play the role of such facets as separate eyes. An example is the side eyes, the main task of which is to warn their owner about the imminent danger.

Force of sight

The main eyes of the spiders are able to see even what the person does not distinguish. In particular, the sensitivity of these creatures to ultraviolet has been proven. Almost 6 thousand species of horse spiders have this ability, which, unlike other representatives of arachnids, prefer not to expect a victim in an ambush, but, on the contrary, actively hunt it.

The weak eyes are possessed by spiders, spiders who catch the victim with the help of the web. Their vision allows you to capture the movement of relatively large objects (moths, flies), to respond to changes in direction and intensity of light.

Eye features

As far as separate species of spiders differ in the number of pairs of eyes that they have, these organs of vision are different in structure and purpose. Genuine interest among zoo-ophthalmologists is caused by spiders of the Salticidae family, in which the main (front) pair of eyes not only has the largest eye lenses among other spiders, they also look like a telescope in their form.

Scientists have determined that no matter how many eyes a spider has (a cross, a crab spider, a sand or other species of these invertebrates), all eyes function as a single organ. First, the presence of a potential victim (flies) determine the rear or side eyes. This happens in the distance between the spider and the fly, constituting not less than 20-25 cm. Then the main eyes come in, to which the main focus is transferred. They determine that in front of the spider there is a desired object of hunting, and not a foreign object.

Thus, the answer to the question of how many eyes a spider requires counter clarifying questions - what kind of spider and which habitat lives in? Only after these parameters have been determined can an exact answer be given to the question.

What are the eyes of spiders

The correct answer to this question would be b) 4 pairs of simple eyes. They are located like an arc and at the same time they are set low enough - in the area of ​​the head and chest. In this case, the eyes are divided into 2 main types: main and side. At the same time, there are no muscles in the side eyes. But they are equipped with mirrors, which help to see the approach of objects from the sides. The main eyes almost always have muscles, though they are not very developed and can only move in one direction. Nevertheless, this system provides the spider with a good overview, which is enough for him to organize the hunt.

What many other insects and spiders do not have a color vision. Of all species, only the horse spider can distinguish some shades. In general, the vision of the so-called stray spiders is most developed. This is due to the fact that they are constantly moving and do not sit motionless on the web, like a net. In addition, they are more active in the daytime, when vision is more in demand than at night.

Pairs of spider eyes

A spider may have a different number of eyes depending on the species to which it belongs. Their number can vary from two to twelve. Some arthropods do without organs of sight. For example, cave spiders, spending their entire lives in the dark, do not have eyes, as they simply do not need them.

Although most of the spiders have eight eyes, arranged in two rows, vision in the lives of these animals is far from the main role, and, despite such a number of visual organs, they see weakly. A spider that can see an object at a distance of thirty centimeters can already be considered a keen eye. However, the vast majority of spiders do not need good vision. They weave a web, where they wait for their prey.
The fact that a mosquito or a fly caught in their network, these arthropods learn from the vibration of the web, which creates a fluttering victim.

The structure of the eye of the spider

Numerous organs of vision of the spider do not work equally. The middle pair of eyes is usually larger than the extra eyes. The main organs of vision are devoid of mirrors, which reflect sunlight, but on the other hand, bundles of muscles are attached to them, thanks to which the eyes can move. The lateral organs, in contrast, are provided with mirrors, but lack muscle bundles.
Apparently, this is due to the fact that the eyes perform different functions: the front of the hunting species monitor the prey, and the lateral - watch the approach of danger.

Eagles among spiders

There is, however, a group of spiders that have extremely sharp eyesight. These are roving racehorse spiders that do not sit still, waiting for their prey, but are actively engaged in its search. The sharpness of these representatives of arthropods is comparable to that of a person. In addition, they are able to distinguish colors, which is not typical for such primitive animals.

The racers have well-developed eye muscles, which allows these animals to follow the prey, while the main eyes are equipped with a large lens and are somewhat elongated like a telescope. Lateral eyes allow the stray spider to capture movement from the side, behind itself and above itself. Despite the fact that the eye of this spider eight, and they have different functions and show a different picture, together they act as a coherent visual apparatus, ensuring the survival of these small animals.