The term ‘Echinodermata’ is derived from Greek words ‘echinos’ meaning ‘spiny’ and ‘dermos’ meaning ‘skin’. The representatives of phylum Echinodermata are absolutely marine organisms and this phylum contains about 7,000 known living species. Among them, notable species are sea urchins, brittle stars, sand dollars, sea cucumbers, sea stars, etc. Scientists did not trace any freshwater or terrestrial echinoderms till now. Echinoderms are unique shaped colorful organisms. They have well-developed organ systems which are ecologically and geologically very important. The water vascular system is the very important key feature of echinoderms through which circulation of nutrients, gaseous exchange, and waste elimination takes place. They have a pentamerous radial symmetrical body with calcareous endoskeleton and their body size ranges from less than an inch to over three feet in diameter. Under the skin of echinoderm`s body, many small plates overlap and forms calcareous endoskeleton. Their body also bears podia which are small extensions of flesh by which water vascular system is operated. In this case, water pressure, body muscles and nervous system also play an important role to control water vascular system.
General Characteristics of Phylum Echinodermata
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Classification of Phylum Echinodermata
Phylum Echinodermata is divided into the following five classes:
Examples: Asterias rubens (Common Starfish), Astropecten articulates (Royal starfish)
Example: Ophiothrix fragilis (Brittle stars), Ophioderma longicauda(smooth brittle star)
Examples: Echinus esculentus (Common sea urchin), Echinarachnius parma (the Common Sand Dollar)
Examples: Cucumaria miniata (Orange sea cucumber), Holothuria leucospilota (the black sea cucumber)
Examples: Antedon mediterranea (Mediterranean feather star), Rhizocrinus lofotensis
Echinodermata makes the largest animal phylum with about 7000 living species. They provide many benefits to human beings. Sea urchins and sea cucumbers are very delicious food for many people and some have medicinal value. Besides these, aesthetically, they have brilliant varieties of color forms which provide a source of amazement and enjoyment to human beings.