A new species of poisonous box jellyfish has been discovered in Singapore

A new species has been discovered off Sentosa Island. Its name is related to the old Malay name of the island - Pulau Blakang Mati, which is usually translated as "the island of death behind". Researchers emphasise: the jellyfish looks similar to other species of the genus Chironex, so without detailed analysis it was easy to mistake it for an already known species.

Importantly, this news does not mean that Singapore's beaches have suddenly become more dangerous. Rather, scientists have clarified which species of box jellyfish live in local waters. Such data is needed to better understand where and when dangerous jellyfish can occur and how to reduce the risk of contact with them.

Details

Box jellyfish are named for their body shape: their "dome" resembles a box or cube. In English-language texts, some members of this group are called sea wasps - "sea wasps" - because of their strong venom.

Researchers from Tohoku University and the National University of Singapore collected jellyfish of the genus Chironex in the coastal waters of Singapore. Among them was a new species - Chironex blakangmati. It was found off Sentosa, along the Singapore Strait.

At first glance, the new jellyfish resembled Chironex yamaguchii, a species previously known from Japan. But genetic analyses showed it to be a separate lineage. Morphological study, i.e. comparison of body structure, confirmed the differences.

The main difference turned out to be in the details of the structure of the lower part of the jellyfish's "bell". In known species of Chironex there are definite channels extending from the edge of the structure involved in the jellyfish's movement. C. blakangmati has no such channels. It may sound like a small thing, but it's details like these that help biologists distinguish closely related species from each other.

Scientists also reported the first record in Singapore of another species, Chironex indrasaksajiae, previously known from the waters of Thailand. It was found in the Straits of Johor and Singapore Straits around the Singapore mainland. This suggests that the distribution of box jellyfish in the region is still poorly understood.

Box jellyfish differ from many other jellyfish in that they don't just passively drift with the current. Chironex have a muscular structure that helps them actively swim and complex eyes that they use to orientate themselves and move towards prey.

Why it's important

The discovery isn't just important for systematics. Box jellyfish can pose a risk to people who swim, dive or work in coastal waters. The more accurately scientists know which species occur in a particular region, the better they can assess seasonality, locations of occurrence, and potential danger.

The new species also shows that even in the waters of well-studied Singapore, there remain unknown or poorly recognised animals. Sometimes a species can hide "in plain sight" for years simply because it is too similar to relatives.

That said, there is no need to jump to panicky conclusions. The study describes a new species and clarifies biodiversity, but does not prove that C. blakangmati has already caused fatalities. More data on its venom, abundance, seasonality and human contact are needed to assess the real risk.

Background

The genus Chironex includes large and venomous box jellyfish. The best known members of this group live in the tropical waters of the Indo-Pacific region. They are almost invisible in the water, and their tentacles can cause severe burns.

This is why studying these jellyfish makes practical sense. It is not just a description of a new marine animal: such data helps lifeguards, environmentalists and beach safety experts to understand when and where the risk of encountering dangerous jellyfish may be higher.

The researchers emphasise that there is still a lack of data on Southeast Asian box jellyfish. The new work simultaneously describes a fourth species of the genus Chironex and extends the known range of the Thai "sea wasp" C. indrasaksajiae to Singapore.

Source

Iffah Iesa, Cheryl Lewis Ames, Nicholas Wei Liang Yap, Danwei Huang, "Chironex box jellyfishes (Cnidaria: Cubozoa: Chirodropida) in Singapore: Chironex blakangmati, new species, and range extension of C. indrasaksajiae", Raffles Bulletin of Zoology, 2026. In the study, scientists examined box jellyfish of the genus Chironex collected in Singapore's coastal waters. A new species, Chironex blakangmati, was described from specimens from Sentosa Island. The authors compared its DNA and body structure with other species of the genus, and also recorded Chironex indrasaksajiae for the first time in Singapore.