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Starfish: one of the best known echinoderms
What they are - definition
The echinoderms are the beings of the phylum Echinodermata (echinos, thorn; derma, skin), usually found at great depths.
Summary of the main features of the echinoderms:
They are free-living marine animals, except for the crinoids that live fixed to the rocky substrate (sessile) and with radial symmetry that also contains their exception: the sea feathers, which move around the cumin.
As an example, we can cite the echinoderms: starfish, holoturia and sea urchin. This phylum appeared in the recent Cambrian period and has about 7,000 living and 13,000 extinct species.
Counting on Concentricycloideas, the currently living species of this phylum fall into the following classification:
- Echinoidea (sea urchin and beach crackers)
- Asteroidea or asteroids (starfish)
- Concentricycloidea, noted for its unique vascular system; two species; recently separated from Asteroids.
- Ophiuroidea (ofiuro)
- Holothurioidea (holoturia or sea cucumber)
- Crinoid (sea lily)
Echinodermal Nervous System
These living things have a fairly simple central nervous system, with a limited nervous network, whose neurons are not connected to the central organs. Although they have no brain, some animals of this phylum have ganglia.
reproduction
Although they have different sexes, these beings reproduce without physical contact, that is, their reproduction occurs through the release of egg and sperm into the water, so fertilization occurs externally.
Regeneration
Many echinoderms have an extraordinary capacity for regeneration, such as the starfish, which when cut in many parts, is able to regenerate after a few months.
Biological curiosity:
Echinodermata It is the largest animal phylum that has no representation in freshwater or terrestrial life.
Sea urchin: another example of echinoderm animal.
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