l>Morphology the EchinodermataEchinodermata: MorphologyEchinoderms have actually been compared to living, moving castles. Castles room made of interlocking blocks, with a single main entrance and numerous slit windows for air and also for defense. Echinoderm skeletons are made up of interlocking calcium lead carbonate plates and also spines. This skeleton is fastened by the epidermis and also is hence an endoskeleton. In some, such together sea urchins, the bowl fit with each other tightly. In others, such as starfish, the bowl are much more loosely bound, and in sea cucumbers the plates space usually microscopic. However whatever their shape,the key of echinoderms have a really typical microstructure: electronmicroscopy reveals them come be, not solid blocks, but fine networks ofcalcium carbonate creating a structure well-known as stereom. Every skeletal aspect of an echinoderm is actually a single crystal the calciumcarbonate, very carefully branched and also structured.Click ~ above this picture of a sea urchin bowl to view the entireimage!Image taken by the snucongo.org environmental Scanning Electrom MicroscopeBetween the skeletalplates, a variety of special structures protrude, with which the echinoderm breathes, moves, and also defends itself. Typically, these space tube feet, pedicellaria, and also gills.All echinoderms have actually a water-vascular system, a collection of water-filled canals branching indigenous a ring canal that encircles the gut. The canals result in podia, or tube feet, which space sucker-like appendages the the echinoderm have the right to use come move, fixed the substrate, or manipulate objects. These pipe feet are extended and also retracted by hydraulic push in the water-vascular system. Pedicellaria space small, snapper-like skeletalelements the are offered by the echinoderm come keep little organisms native settlingon that is body.Echinoderms additionally have a spacious coelom (an open, fluid-filled body cavity lined through tissue), big gonads, and (usually) a finish gut. Many starfish have actually the peculiar capacity to feed by turning the stomach inside out with the mouth; sea urchins scrape birds from rocks with five big teeth arranged in a structure recognized as "Aristotle"s lantern." Echinoderms (except holothurians) typically lack respiratory tract systems, and many have only rudimentary circulatory systems; the water-vascular system takes over few of the attributes of this systems. Nervous and sensory equipment are generally poorly occurred in echinoderms.Source:Hyman, L. H. 1955. The Invertebrates.

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Volume IV: Echinodermata.McGraw-Hill, new York.