What are arthropods: characteristics, classification and examples

Arthropods are invertebrate animals that constitute themost numerous and diverse edge within the 29 edges that make up the Animalia or Animal Kingdom .

They appeared on the face of the Earth approximately 600 to 500 million years ago . Various evolutionary studies have revealed how arthropods most likely evolved from some type of worm similar to the marine annelids that exist today, so that the differentiated segments that characterize arthropods could be an evolution of the homologous segments of these worms.

In the next sections we will see in detail what are the main characteristics that define this extensive group of animals, as well as many examples of arthropods to get to know them more closely.

Arthropods have many common features that allow grouping various invertebrate animals that at first glance may appear very different from each other, but in reality they all share a series of anatomical and functional characteristics that allow them to be grouped within the Arthropod phylum . Let’s see in the following list what are these main characteristics of arthropods :

• They present a body made up of different articulated segments, appendages, and an exoskeleton.
• Respiration in arthropods is usually through tracheal systems that allow gas exchange with the atmosphere, although some groups of aquatic arthropods have gill respiration . Learn about Tracheal Breathing Animals here.
• They have a digestive system adapted to the different hunting and digestion strategies that characterize each type of arthropod, sometimes having poisonous glands that allow them to attack their prey more effectively or the ability to digest their food with the help of substances. Chemicals.
• The reproduction of arthropods is usually sexual, with the intervention of female and male organisms, although some species are hermaphrodites and others are capable of reproducing asexually. Those that do it by asexual reproduction , mostly do it through parthenogenesis and other methods that allow the survival and development of their individuals.
• They have had great evolutionary success, since they have conquered different habitats: from the marine and fresh aquatic systems, as well as the subsoil, the land surface and the air.
  

As mentioned above, arthropods make up the phylum Arthropods. This immense edge is divided into four subphiles within which different classes are included. Let’s see them in detail in the following complete classification of arthropods :

• Subphylum Unirrámeos: Class Diplópodos (millipedes), Chilopods (centipedes), Pauropods (small animals with 9-10 pairs of legs and no eyes), Symphyla (garden centipedes), and Insects.
• Subphylum Crustaceans: Class Branchiopods (cladocerans and other small crustaceans with white blades), Remípedos (strange blind crustaceans that live in caves at great depth, in marine ecosystems), Cephalocarids (few species of benthic crustaceans), Maxilopodos and others ( small crustaceans with a reduced abdomen), Ostracods (microscopic, with valves) and Malacostraceans (crustaceans better known as lobsters, crayfish, etc.).
• Subphylum Cheleicerates: Class Arachnids (spiders, scorpions and mites), Merostomados (horseshoe crabs), and Picnogónids (sea spiders).
• Extinct subphylum Trilobitomorphs: it included the fascinating trilobites.

As we have seen in the previous section, it is possible to differentiate various types of arthropods according to their anatomical structures and phylogeny. Within this incredible variety, the myriapods are the simplest and most primitive arthropods (they only have a head and thorax), while arachnids have the head and thorax fused, giving rise to the “cephalothorax”, and the insects appear as arthropods. more evolved, in which the head is composed of the fusion of six different segments in which antennae and mouthparts are inserted, together with a thorax with three segments and an abdomen with eleven, both parts with appendages and structures associated with locomotion and other vital functions of these amazing invertebrates.

Let’s see in the following list many examples of the most surprising arthropods that we can find in each and every one of the different ecosystems on the planet:

• Mites
• Spiders
• Crabs (marine and freshwater)
• Horseshoe or pan crabs
• Shrimp
• Spider crabs
• Crawfish
• Cladoceros
• Mealybugs
• Copepods
• Cockroaches
• Beetles
• Scorpions
• Krill
• Lobsters
• Dragonflies
• Praying mantis
• Butterflies
• Myriapods