The Arthropoda phylum is an extremely diverse phylum, being considered the largest group of animals on the planet! Among the infinity of animals in this phylum, we can mention butterflies, cockroaches, spiders, scorpions, flies, centipedes, dragonflies and lobsters.
These animals have very important characteristics for their adaptive success. One of the key features for this success is the presence of the exoskeleton. The term exoskeleton means external skeleton. The exoskeleton works as a protection against friction, pathogens, predators and environmental variations. In addition, it provides structural support and shape to the animal's body.
The exoskeleton of arthropods is formed by chitin, a polysaccharide composed of N-acetylglucosamine monomers. In crustaceans, in addition to the presence of chitin, there is impregnation of calcium carbonate (CaCO3). That's why crabs and crabs have an extremely rigid carapace that is difficult to break.
The presence of this rigid exoskeleton is undoubtedly an extremely important feature for arthropod survival. However, this feature does not only have positive points. With this rigid carapace, it becomes impossible for the animal to grow as it occurs in other groups. The arthropod needs to change its exoskeleton in order to grow. This process is called
changes or ecdysis.
Molting or ecdysis allows the animal to grow
Moulting takes place in several stages. In the intermud, the animal lives normally, carrying out all its activities. When it reaches a size in which exoskeleton exchange is necessary, the pre-moulting phase begins. This phase is characterized by the production of a new exoskeleton that will coat the animal. The animal will then have two exoskeletons: the old and the new. However, the new skeleton will remain soft. Moulting then takes place, which is the moment when the old exoskeleton is eliminated. After elimination, the arthropod will have only the new, soft exoskeleton. From there, the arthropod will expand its body, using air or water. When the new exoskeleton hardens, this water and air will be replaced by the animal's tissues.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-exoesqueleto-quitinoso.htm
