Spiders are a type of arthropods that belong to the arachnids. Currently, up to 45,000 species of spiders have been categorized, within 109 families. They are characterized by their unmistakable morphological structure. Surely you have wondered how many legs or eyes the spider has, as it is one of the traits that causes the most fear in people.
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Prosoma or cephalothorax
Spider body parts: This is the first of two parts that make up a spider’s body, separated by a “waist.” It is also called a cephalothorax, because here is its cephalization along with its sensory organs necessary to interact with its environment and also its region analogous to a thorax.
This is the anterior part of the spider and it contains:
- Simple eyes : that can be found multiplied in several pairs . Spiders often seem terrifying animals to us, but when you see the cute eyes with “lashes” of the salticides you will think differently. The arrangement, number, and color of spider eyes are important traits that aid in species identification and classification. In fact, many people wonder how many eyes spiders have, and their number can vary from 8, 6 or 4. There are even some that have no eyes or lose their vision because they live underground.
- Mouth : attached to the esophagus.
- Brain : which receives the impulses and processes the information.
- Respiratory crop : but it does not replace the lungs.
- Digestive receptacle , analogous to the stomach.
- Circulatory system : which supplies the prosoma with hemolymph, a liquid equivalent in arthropods to blood. Discover What are arthropods: characteristics, classification and examples , here.
- Chelicerae : with the venom glands located inside.
- Pedipalps : This is your second pair of appendages.
Spider parts: Opisthosoma or abdomen
Spider body parts: This is the posterior region of spiders and is also called the abdomen. Most of the systems for internal functions are concentrated here . Such are:
- Digestive gland : since they cannot digest their “solid” victims and they have a small digestive system, what they do is insert a poison into their prey to liquefy and absorb them later. It should be noted that spiders are carnivorous and their favorite food is insects.
- Excretory system : Composed of the Malphigi tubes, the stercoral sac, and the anus.
- Reproductive system : with oviduct, seminal receptacle and vagina, or spermatic duct, copulatory organ and testicles.
- Rows : with associated glands for silk production.
- Continuation of the circulatory system : with heart, a hole called ostiole to allow the passage of hemolymph, lateral blood vessel and sac of the pericardium.
- Respiratory system : with only one book lung, whose name refers to its shape as book pages parallel to each other, in order to optimize, organize and make this organ more efficient. Here gas exchange takes place and it has an opening for transporting the results of respiration. Hemolymph is also stored here.
Spider parts: Legs
Spider body parts: They are the locomotive appendages for the displacement of these organisms. Spiders have four pairs of legs, that is eight. They belong to the arthropods, which means that their eight legs are jointed . Each one is made up of several fragments, called knuckles, which come out from the bottom of the prosoma where they have a small muscle. Beginning with the part attached to the body, these parts are called:
- Pretarsus: with one or two nails.
These joints perform the function analogous to muscles in vertebrates , since arthropods need the help of some mechanism to move as they lack proper muscles. They are divided into as many fragments to have greater control and flexibility when walking and even jumping.
The legs are also aided by hydraulic pressure to move, in which hemolymph pressure is used to move their legs outward. The prosoma accumulates a large content of hemolymph and for this reason the legs are connected to this part of the spider. The exoskeleton, that is, the hard layer that covers the insects and provides them with support, plays with this hydraulic pressure so that the spiders can exert force outwards, helping their locomotion.
Spider parts: Chelicerae
Spider body parts: These structures are mouthpieces , similar to small very sharp fangs, used by spiders as a hand or tool to take their food . They are located before the mouth and are arranged in a pair. They can have different shapes, such as tweezers, fangs or knives.
They also store their venom here , useful for immobilizing prey. Depending on the spider, the venom may or may not be lethal to humans. These chelicerae have a nail that comes out only when it is going to inject poison, functioning as an advanced needle.
Spider body parts: They are another type of appendages very similar to the legs , since they are composed of the same fragments. The difference is that they do not touch the ground and have a tactile and olfactory function to recognize their surroundings (instead of locomotive) although some spiders can use them to move, like tarantulas, for example. There are only a couple of them and they are found after the chelicerae and before the legs.
Spider body parts: Spiders normally have three pairs of spinnerets , although the most primitive have eight in total. In these there are several and different glands for the production of spider silk or cobweb, a hard protein but at the same time elastic. These glands have ducts towards the end of the row so they can be used by the spider. The product is an extremely flexible, water-repellent and very resistant silk, used to capture or wrap prey , move through the air or to build nests.