Arthropods

To talk about arthropods we must remember what invertebrate animals are . This type of animal is one that does not have a backbone and also has an internal skeleton that is articulated . Within the great classification that invertebrate animals have, we can find arthropods, animals that have articulated legs and their body divided into three different parts .

Definition

Arthropods are animals that belong to the group of invertebrates , which are found in greater numbers in the animal kingdom . They are animals that have their body covered by an exoskeleton , which is known by the name of the cuticle and a series of ostensible segments located in a linear fashion that have articulated appendages . They are the animals that we generally know by the name of arachnids , insects and crustaceans .

Characteristics of arthropods

The most representative characteristics of arthropods are the following:

• They have an exoskeleton made up of different layers, a superficial one made up of proteins and lipids, a thicker or procuticle and a more rigid one known as the endocuticle .
• It has the ability to change its exoskeleton through a process known as ecdysis .
• They can be classified depending on the number of legs they have.
• It has simple eyes that have a simple retina and a transparent cornea that covers them, although they can also be made up of different elements positioned radially that can point in different directions.
• They are the most numerous animals that exist on the planet and they inhabit any environment .
• They can have different types of food .
• Their bodies are divided into segments or well differentiated sections that are head, thorax and abdomen .
• Their exoskeleton is made of chitin , which provides protection against the elements.
• They do not have blood, they have an internal substance known as hemolymph .

Classification

Arthropods can be classified depending on the number of legs they have, and they are classified as follows:

• Arachnids : they are arthropods that are characterized by having two jaws in their mouth one above the other, their body is divided into two parts, they do not have antennae and they also have 8 legs in the prosoma. They breathe through tracheas and in this group we find spiders , scorpions, mites and opiliones .
• Insects : they are the most varied and numerous group . Its body is divided into a head , thorax and abdomen , they have antennae , jaws and three pairs of legs. Their breathing is tracheal and the dominant group lives on earth . ranging from cockroaches, butterflies and fleas, to praying mantises and dragonflies.
• Crustaceans : they are arthropods that have jaws , antennae , gill respiration and their body is generally divided into two parts, the cephalothorax and the abdomen . They have a shell and undergo metamorphosis . They are mostly aquatic animals , such as lobster or crab, although we can also find examples such as the moisture scale, adapted to the land.
• Myriapods : they are terrestrial arthropods that have a head with antennae and jaws . They also have a trunk formed by several segments and have a type of tracheal respiration . There are the diplopods that have a cylindrical bodyand two pairs of legs in the segments (millipedes) and the chilopods that have a flattened bodyand only one pair of legs in each segment (centipedes). Endowed with multiple legs and long bodies , as well as chelicerae, such as centipedes and millipedes.

Habitat

These types of animals can be found in all kinds of places . They can live in mountains, in forests, rivers and bushes, in lakes and seas and even in urban environments. Some of them can even survive in extreme habitats such  as deserts,  although due to their size, they do not withstand the cold very well, so their presence decreases as we get closer to the poles. We can also find crustaceans , which inhabit the sea and rivers and need humid environments to survive.

Arthropod diet

Arthropods are animals that have managed to evolve with the passage of time and have different mechanisms of feeding . For this reason, arthropods can be:

• Herbivores : they are arthropods that feed on algae , leaves , stems , fruits or other substances that are plant-like including even wood .
• Predators : they are the type of arthropod that feeds on other animals , they can even feed on animals of the same species which makes them active and fearsome predators for many, such as spiders or scorpions.
• Parasites : this kind of arthropod can feed on different substances that come from other larger animals, such as blood , for example when they extract it directly from their bodies. An example of this type of animal are fleas, lice and ticks .
• Decomposers : they are arthropods that feed on organic matter that is in a state of decomposition , the body of dead animals , fallen leaves or food remains , waste , etc. For example, flies and cockroaches.

Digestive system

Your digestive system is divided into three well-differentiated regions that are the stomodeum , the mesodeo, and the proctodeo . Stomodeus and proctodeum are located at the anterior and posterior end of the animal, respectively, and are covered with a cuticle that is renewed each time the animal molts. The middle part of the digestive tract called the mesodeo , comes from the endoderm and is responsible for producing digestive secretions and is the place where most of thenutrient absorption .

Breathing

Some of them, due to their size, do not need respiratory organs. In the case of aquatic arthropods , they have gills , and secondary gills have also been found in the aquatic larvae of some insects. Many of them can breathe through internal organs and their breathing can be done through the trachea or book lungs .

Insects have a network of ducts or a tracheal system that communicate outside through holes called spiracles . Active ventilation is observed in some types of arthropods , with cyclical movements of inspiration and expiration . The lungs in a folded book have internal structure that allows the exchange of gases , and open to the outside by own independent openings.

Reproduction

Most of the arthropods that exist have a form of sexual reproduction and the development of their young can be direct or indirect . Females that have been fertilized by males lay their eggs in a specific location. When the birth process occurs directly , a large number of individuals are born with an appearance equal to that of the adult parents but with a smaller size. When the process is indirect , a larva will be born that will have to go through a series of profound changes to complete the process of metamorphosis .

It is important to mention that the primary sexual characteristics are made up of the genital organs , which are different in the male and the female. In addition, it also has secondary characteristics such as height and behavior that make it possible to distinguish between the different sexes.

Breathing

Arthropods have adapted to different types of environments and environments, so that respiration can occur through lungs or tracheae (air) or also through gills , in the case of animals that live in water, as in the case of marine crustaceans, such as lobsters. Arthropods that have lungs have them located in a structure that has independent openings . Animals that are provided with tracheas, as they are mostly, breathe through a series of tubes that communicate to the outside .

Nervous system

Your brain is divided into two parts, the proto and the tritobrain, which are located above the esophagus. They have a large number of mushrooms and hairs of different sizes that serve as receptors for external stimuli , mainly tactile, gustatory, auditory and thermal. They also have longer and more mobile hairs that are responsible for perceiving the different air currents and vibrations .

Arthropod locomotion

Invertebrate animals have managed to develop a large number and variety of locomotion systems . In the case of arthropods, they have an exoskeleton which is made up of legs that have joints that allow and facilitate movement and moving from one place to another.

Arthropod diseases

Arthropods that feed on human or animal blood have become a serious public health problem . Their bites are usually very annoying, painful, cause redness and a rash on the skin, as well as being vectors of a large number of diseases . There are vectors that are transmitters of infectious agents that can transmit Rocky Mountain spotted fever , encephalitis , yellow fever , and dengue . Also the killer bug that causes Chagas disease and the flea that produces the bubonic plague.

Some of them cause diseases and annoyances such as lice, and cimicia, which is produced by the flea. Many of them sting as in the case of scorpions, wasps and spiders. Many arthropods are also parasites in both man and animals, fleas, ticks and horseflies can transmit diseases .

Importance

Arthropods are animals that can represent economic importance in many countries as they represent a good form of commercialization, as is the case with crustaceans, which include shrimp, lobsters and other marine species. Some of them provide us with great benefits such as bees , which provide us with honey , wax and that helps the pollination of plants, so that they can grow properly. Others also help with the biological control of some pests .

Examples of species

Examples of arthropod species include the ant, scorpion, lobster, centipede, spiders, bees, fleas, cicada, dragonfly, butterflies, scorpions, mosquitoes, flies, among others.

Why are they called arthropods

These animals are called arthropods because they are animals that have their bodies with a series of jointed parts , legs or legs. Also because they have an external skeleton formed by chitin , hard and resistant that gives protection to the animal like armor.