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Echinoderms such as sea urchins and starfish are animals that are characterized by having an endoskeleton and an ambulacral system. They also have bilateral symmetry when they are larvae and radial when they are adults. In addition, some have pedicelaria, which are claw-shaped structures that have various functions, such as defending the animal from predators. Another of the parts that characterize the body of echinoderms is the madreporite, which will be discussed below.
the madreporito
The madreporite, also called madreporic plate, is a plate or valve that regulates the difference in pressure, entry and exit of seawater inside the echinoderm. From the aboral madreporite a channel emerges to the other end of the animal, the oral surface; In turn, this channel connects to a ring full of vesicles that accumulate the water necessary to manage the pressure.
Echinoderms do not possess a blood circulatory system like other animals: they rely on the controlled entry and exit of water into their systems to get their circulatory system working. This system is called the aquifer vascular system or ambulacral apparatus. Said system is made up of several ducts filled with liquid and its opening to the outside is through the madreporite. This a cavity of the echinoderms has the function of locomotion in the animal.
By controlling the entry and exit of water through the ambulacral system and the madreporite, the echinoderm is able to detach or adhere and thus crawl precisely. The one in charge of controlling the ambulacral system is the nervous system of the echinoderm.
exceptions
In the crinoidea class (sea lilies) the madreporite does not exist and instead we find a good number of ducts that replace it; in some cases there are hundreds of ducts. The madreporite of sea cucumbers (holoturians) is not in contact with the outside but is inside the animal.
References
- Fernandez, M. (2007). Organization levels in animals . Available at: https://books.google.co.ve/books?id=sYwUjaSuK0cC&pg
- Garcia, J. (2015). The echinoderms: characteristics and classification . Available at: https://www.infobiologia.net/2015/10/equinodermos-caracteristicas-clasificacion.html
- Astur Nature. echinoderms. Generalities . Available at https://www.asturnatura.com/articulos/equinodermos/general.php .
