Knowra Echinoderm Echinoderm An invertebrate animal in the phylum Echinodermata, found in marine environments. Echinoderms have a water vascular system and, in adults, typically show five-part radial symmetry.
Water vascular system : A fluid-filled network of canals and tube feet used for movement, feeding, and gas exchange in echinoderms. This distinctive hydraulic network powers the tube feet that define much echinoderm activity.
Keystone species : A species whose ecological effects are disproportionately large relative to its abundance. Some sea stars regulate mussel populations and maintain diverse rocky-shore communities.
Sea star : An echinoderm with a central disc and usually five or more radiating arms. Sea stars are familiar predators and scavengers with powerful tube-foot systems.
Cambrian explosion : A period of rapid diversification of animal forms beginning about 539 million years ago. The early fossil record of echinoderms emerges during this major diversification of animal life.
Cnidarian : An invertebrate animal in a group that includes jellyfish, corals, and sea anemones. Cnidarians often have radial symmetry, but lack the echinoderm water vascular system and skeleton.
Tube foot : A small, movable appendage connected to an echinoderm’s water vascular system. Tube feet grip surfaces, move food, and help many echinoderms travel.
Urchin barren : An underwater habitat where dense sea urchin grazing has removed much of the kelp forest. Sea urchin outbreaks can transform kelp ecosystems into persistent barrens.
Sea urchin : A globular echinoderm with a rigid test, movable spines, and specialized feeding structures. Sea urchins graze algae and use a distinctive jaw apparatus called Aristotle’s lantern.
Echinoderm fossil : A fossilized skeletal element or body of an animal from the phylum Echinodermata. Durable calcite plates and spines make echinoderms prominent in many marine fossil deposits.
Arthropod : An invertebrate animal with a segmented body, jointed appendages, and an external skeleton. Arthropods contrast with echinoderms’ internal skeleton and unjointed tube feet.
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