Sea urchins are marine invertebrates belonging to the phylum Echinodermata. These spherical creatures are covered in a rigid shell, called a test, which is protected by numerous movable spines. While the intimidating exterior might suggest otherwise, the sea urchin is considered a global delicacy, particularly in Japanese and Mediterranean cuisine. However, only a small fraction of the nearly 950 known species are harvested for consumption, meaning not all sea urchins are edible.
The Prized Edible Portion
The part of the sea urchin consumed by humans is the gonads, not the roe or eggs. This delicacy is known by its Japanese name, uni, and each urchin contains five distinct lobes of this edible tissue. The color of uni can range from a pale yellow to a deep, vibrant orange.
The flavor profile of uni is a blend of sweet and briny, with a rich, savory umami finish. Its texture is smooth and custard-like, melting on the tongue when fresh. The quality and flavor are influenced by the urchin’s diet, with a steady supply of kelp being optimal, and the coldness of the water in which it is harvested.
Identifying Edible Species
Only about 18 sea urchin species are commercially harvested, with a few dominating the global market. The Red Sea Urchin (Strongylocentrotus franciscanus) is one of the largest and most prized species, found along the Pacific Coast from Alaska down to Baja, California. Its uni is known for its vibrant gold color and robust, rich flavor.
The Green Sea Urchin (Strongylocentrotus droebachiensis) is a smaller species harvested in both the Atlantic and Pacific Oceans, with significant fisheries in the Canadian Maritimes and Maine. Another commercially important species is the Purple Sea Urchin (Paracentrotus lividus), which is widely consumed in the Mediterranean Sea and the Northeast Atlantic.
The Purple Sea Urchin (Strongylocentrotus purpuratus) is also found along the Eastern Pacific coast. These medium-sized urchins yield uni known for its delicate sweetness and smooth, custard-like texture. The European edible sea urchin (Echinus esculentus) is also consumed, but it is not among the preferred species because its gonads are often white, which is less desirable to consumers who prefer the orange hue.
The Inedible and Dangerous
Most sea urchin species are inedible, falling into two main categories: undesirable and dangerous. Undesirable species are typically too small, have a low yield of uni, or possess a poor flavor profile that makes them commercially unviable. These species pose no threat but offer little reward for harvesting.
A small number of species are venomous, delivering toxins through their spines or specialized structures. The Flower Urchin (Toxopneustes pileolus) is one of the most dangerous, found throughout the Indo-West Pacific. This species delivers venom not through its short spines, but through numerous flower-like organs called pedicellariae.
The venom from the Flower Urchin contains a glycoprotein that can cause severe pain, respiratory problems, and even paralysis. Other venomous genera, such as Diadema and Tripneustes, possess long, sharp spines that can easily break off in the skin and inject painful venom.