Marine scientists have identified a new species of highly venomous box jellyfish living near a Singapore island once known as Pulau Blakang Mati, a Malay name that translates to “Island of Death Behind.”
Researchers named the species Chironex blakangmati after the island’s former name, instead of its current name, Sentosa, which means peace and tranquility. The species was identified from specimens collected in waters near the island in 2020 and 2021. The discovery was published May 15 in the journal Raffles Bulletin of Zoology.
One of the ocean’s most dangerous jellyfish groups
Scientists said C. blakangmati belongs to the Chironex genus, a group known for producing some of the world’s most dangerous jellyfish. Their tentacles contain microscopic stinging cells called nematocysts that inject powerful venom.
Severe stings can trigger extreme pain, heart problems, and, in some cases, death. Box jellyfish have been linked to fatal incidents across parts of the Indo-Pacific region, including Australia and Southeast Asia.
Unlike many jellyfish that drift with currents, Chironex species can actively swim and hunt prey. Researchers said the animals use strong muscles and complex eyes that help them detect movement and navigate through the water.
Genetic and physical differences confirmed the species
Researchers initially believed the Singapore specimens belonged to another dangerous species, Chironex yamaguchii. However, detailed genetic testing and anatomical comparisons revealed that the jellyfish represented a separate species.
Scientists have identified a new highly venomous box jellyfish species near Singapore’s Sentosa island — once known as Pulau Blakang Mati, or “Island of Death Behind.” pic.twitter.com/hnJWr7R94Z
— Tom Marvolo Riddle (@tom_riddle2025) May 20, 2026
Study co-author Cheryl Ames said the Singapore specimens closely resembled C. yamaguchii, a species she first identified during earlier research in Okinawa, Japan.
To confirm the differences, Ames reexamined preserved samples of C. yamaguchii stored from her earlier work.
Researchers also found a key anatomical difference. The newly identified species lacks branched canal structures near the lower part of its bell-shaped body. Those structures are present in other known Chironex species and help support the muscles used for swimming.
Scientists said the anatomical differences, together with the genetic evidence, confirmed C. blakangmati as a distinct species.
Thai sea wasp was also detected in Singapore waters
The study also documented Chironex indrasaksajiae, commonly called the Thai sea wasp, in Singapore’s waters for the first time.
The species is usually found in Thailand and is also considered highly venomous. Researchers said its appearance in Singapore suggests scientists still know relatively little about the distribution of box jellyfish across Southeast Asia.
Study co-author Danwei Huang said the findings provide new insight into the diversity of Chironex jellyfish in the region.
Researchers said improving knowledge of where dangerous box jellyfish live could help authorities reduce serious injuries and deaths linked to stings in coastal areas.
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