Sea urchin

A marine invertebrate in class Echinoidea, with a hard, rounded skeleton called a test and movable spines. Tube feet and specialized mouthparts help it move and feed.

Echinoderm: A marine invertebrate in the phylum Echinodermata, typically with a water vascular system and adult five-part symmetry. Sea urchins belong to this larger group, alongside sea stars and sea cucumbers.
Sea urchin grazing: The consumption of algae and other surface growth by sea urchins, often using scraping mouthparts. Grazing is a central way urchins obtain food and alter underwater habitats.
Sea urchin fishery: The harvesting and sale of sea urchins, especially their edible gonads, known as roe or uni. Commercial demand for roe shapes harvest pressure and management of urchin populations.
Purple sea urchin: Strongylocentrotus purpuratus, a Pacific sea urchin common along the western coast of North America. Its abundance and grazing have made it a prominent species in kelp-forest ecology.
Kelp forest: A coastal marine ecosystem dominated by dense stands of large brown algae called kelp. Kelp forests provide habitat and food that can disappear under intense urchin grazing.
Aristotle’s lantern: A complex set of five jaws and supporting muscles used by many sea urchins for biting and scraping. This mouth apparatus lets many urchins graze algae from hard surfaces.
Sea urchin locomotion: Movement by sea urchins through coordinated action of tube feet and movable spines. Urchins can travel across surfaces despite lacking limbs or a centralized brain.
Sea urchin aquaculture: The cultivation of sea urchins for food or research in controlled conditions. Farming offers ways to supply roe while reducing reliance on wild harvests.
Long-spined sea urchin: Diadema antillarum, a Caribbean sea urchin distinguished by exceptionally long, slender spines. Its population collapse contributed to major changes in Caribbean reef algae.
Trophic cascade: An ecological chain reaction in which changes at one trophic level alter populations at other levels. Predator changes can release urchins from control and indirectly reduce kelp.

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