Concept in Definition ABC

The animals with the highest number of species are the arthropods, which are divided into five groups: crustaceans, centipedes, myriapods, arachnids and insects. Despite their anatomical differences, all these animals share two essential characteristics: they are invertebrates and do not have an internal skeleton. Is singularity is related to the etymology of the term, since arthropods means jointed feet or legs (arthron is equivalent to joint and podos equals foot).

Main physiological aspects

Most arthropods have the body divided into symmetrical segments and at the same time have an external skeleton, which serves as a protective element against the threat from other predators. The body of some arthropods does not grow to the same velocity than their external skeleton, so they change it for a larger one in a process known as molting.

From an evolutionary point of view, arthropods have adapted to all types of environments by various factors: the segmentation

of its organism, the exoskeleton, the articulated appendages and some powerful sensory structures. These factors allow them a great mobility and a remarkable efficiency to survive.

Some arthropods are terrestrial and others aquatic. Terrestrial animals (such as the scorpion) breathe through tracheae, while aquatic species (such as lobster) breathe through gills. As for his feedingIt is also very diverse, as there are herbivorous arthropods (the caterpillar would be an example), carnivores (the praying mantis) and omnivores such as wasps.

With respect to reproduction, arthropods are internally fertilized and oviparous, that is, they lay eggs to reproduce. Larvae hatch from their eggs and undergo various changes (metamorphosis) until they become adults.

The question of the zoological division of arthropods depends on the number of legs

Due to the large number and variety of arthropods, zoologists classify them into four large groups depending on the number of legs they have.

Insects such as flies, ants or lice have 6 legs, scorpions and spiders are part of arachnids and have 8 legs, crabs or spiders. Prawns are crustaceans and have 10 legs and, finally, myriapods have more than ten legs and their bodies are very elongated (the caterpillar and the centipede are part of this group).

Photos: iStock - Edsel Querini / blakisu

Topics in Arthropods