Murasaki uni nigiri

Purple sea urchin (Murasaki uni)

【Nigiri sushi: Gyoran】
What is Murasaki uni?
Purple sea urchin (Murasaki uni, Heliocidaris crassispina) is distributed along the coasts of Honshu and Kyushu. It mainly inhabits relatively warm coastal waters around Japan, and its spawning season is from May to August. Its northern distribution limits extend to the Pacific coast near Oarai in Ibaraki Prefecture and to Fukaura on the Sea of Japan coast in Aomori Prefecture.

It is one of the most common sea urchin species found along the shores of Japan. It is characterized by thick, sharp, dark purple spines, and its shell can grow to approximately 6 cm in diameter. Although it closely resembles Kitamurasaki uni, it is generally smaller in size.

The main harvesting areas overlap largely with those of Aka uni, including Yura on Awaji Island, Hirado and Iki in Nagasaki Prefecture, and the Oki Islands in Shimane Prefecture.

What does Murasaki uni nigiri sushi taste like?
Murasaki uni has been consumed since ancient times in some coastal regions of Japan and has long been appreciated locally as fresh raw uni and sushi. However, because its catch volume and distribution are limited, it is not as widely recognized in the national sushi market as Kitamurasaki uni, which is distributed extensively from regions such as Hokkaido.

Murasaki uni and Aka uni often inhabit overlapping coastal areas and may be caught in the same fishing grounds. However, the flavor of Murasaki uni can vary considerably depending on its habitat, the type of seaweed it feeds on, and other environmental factors. Therefore, it is difficult to define a single characteristic “taste” for this species. Instead, Murasaki uni is best appreciated for the unique flavors and qualities that reflect the individual regions where it is harvested.

In Japan, cold-water Ezobafun uni and Kitamurasaki uni account for approximately three-quarters of the country's total sea urchin harvest. Among the remaining native sea urchin species, Murasaki uni accounts for the largest share, followed by Bafun uni, with smaller quantities of Aka uni, Shirahige uni, and other varieties.

Because Murasaki uni is mainly consumed locally in its production areas, it is relatively uncommon to find it served at sushi restaurants in Tokyo.

Also called Hard-spined sea urchin.

【Temperature of vinegared rice (shari) and sushi toppings】
34～36℃/15～18℃

【Trivia】
・The umami flavor of sea urchin is mainly made up of amino acids and nucleic acids. Some of the amino acids found in this topping are glycine, alanine, valine and glutamine. The sweetness of sea urchin is related to the glycine and alanine content, while its richness comes from glutamine. It doesn’t have a high inosinic acid content, which is a nucleic acid, but the synergistic effects of the inosinic acid and glutamic acid bring out the umami flavor. It also contains methionine, an amino acid, which contributes greatly to the unique flavor that sea urchin is known for.

・In Shimonoseki city, Yamaguchi prefecture, there is an experiment that feeding sea urchin waste vegetables donated by local agricultural corporative. The experiment result of 2018 shows that the sea urchin fed tomato was the tastiest.

【Related contents 】
Global sea urchin resources

What is uni sushi?

Why is it that sea urchin sushi can taste bitter?

List of Nimono, Gyoran and Others

(Revision date: June 26, 2026)