BIOL 321 Lecture Notes - Lecture 29: Water Vascular System, Tube Feet, Echinoderm
18 Nov 2016
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They have secondary body cavity completely lined by epithelium derived by mesoderm. Whole series of eucoelomic compartments within the body. Sea star embryo: archenteron has pushed completely inside. At the point where it pushed in, this becomes the future anus of the animal. The mesoderm (3rd embryonic cell layer) arises form endoderm. Mesoderm from process called enterocoely: water vascular system (wvs)- system of interconnected water filled tubules. External component is manifested as these tube feet. Operates tube feet: calcareous endoskeleton (completely covered over in epidermal epithelium) They are synthesized by cells within the dermis, and are completely covered over by epidermal epithelium. Microporosity: pentamerous radial symmetry (=pentaradial symmetry) Body is organized around central axis consisting of mouth (on opposite side of body) This is shown at least in the adult stage. The shape of the free-living larval stage is different depending on species but even then the larva show bilateral symmetry.
