Sea urchin (biological features and utilization) – Video

This short video was filmed at “Tuna Harbor Dockside Market”, San Diego, USA during the Saturday fish market held on 27 December 2014.

Sea Urchin





Introduction: The name “urchin” is an old word for hedgehog, which sea urchins resemble. Sea urchins are small and spiny animals that are members of the phylum Echinodermata, which also includes sea stars, sea cucumbers, brittle stars, and crinoids. There are nearly 200 different species of identified sea urchin with various shapes, sizes and living in different environments. The red sea urchin is the longest living creature on earth, with some living more than 200 years.

Sea urchins have a certain regenerative ability.  If a spine is damaged or lost, a sea urchin can re-build it.  However, animals would not be able to heal extensive damage such as the test damage.

Feeding habits: Sea urchins are omnivorous animals and therefore feed mainly on algae but can also feed on sea cucumbers along with a wide range of invertebrates, such as mussels, polychaetes, sponges, brittle stars, and crinoids.

Sea urchins are preyed upon by many predators including sea otter, lobsters, crabs, trigger fish, starfish, wolf eels, California sheephead, birds, and humans. Almost all these predators carry particular adaptations (e.g. teeth, pincers, claws) and enough strength that enable them to overcome the excellent protective features of sea urchins as represented by their strong and sharp spines, and poisonous apparatus. Because sea urchin is nocturnal, they will usually hide in holes or crevasses during the day and only feed at night.

Reproduction and life history: A female sea urchin releases millions of 100-150 micron tiny, jelly-coated eggs into the water that are then fertilized by the sperm of the male sea urchin resulting in the formation of sea urchin larvae which is known as a “pluteus”. The larvae require several months to complete its development before sinking to the ocean floor and metamorphose into adult.

The sex of sea urchin cannot be distinguished until adults themselves release their gametes whether eggs or sperms and this occurs at the age of 2-5 years.



As food: Certain species of the sea urchin are eaten in some countries in the Mediterranean, New Zealand, and Japan and by native populations in some continents and on some islands. Traditionally sea urchins are eaten raw, with lemon or used in some sauces and flavor. Wherever sea urchins are eaten, their gonads are served as a delicacy. In Japan, sea urchin and its roe are served raw as sashimi or in sushi. In that regard, Japan is the main importer of sea urchin from the United States, South Korea, and other producers whereas Japanese demand for sea urchin corals has raised concerns about over-fishing.

For aquaria: Some species of sea urchins, such as the slate pencil urchin and others are sold in aquarium stores and recommended for sea water aquariums. In addition to their unique shapes and colors, selected sea urchin species eat and control variety of algae, such as green, red and coralline algae. However, they should be under check as without enough algae to eat they will graze on corals and invertebrates.



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