Scientists discover deadly, highly venomous box jellyfish near Singapore's 'Island of Death Behind'

Scientists have described a new species of highly venomous box jellyfish based on specimens that were lurking near a Singaporean island formerly known as Pulau Blakang Mati, or the "Island of Death Behind," in 2020 and 2021.

The newly described species, Chironex blakangmati, was named after the island's original, ominous name in Malay, rather than its name since 1972, Sentosa, which means "peace and tranquility." That's fitting, given how dangerous the animal is.

C. blakangmati is one of four known species of Chironex box jellyfish, all of which are incredibly venomous. Their stings, delivered via special cells on their tentacles called nematocysts, are so powerful they can kill humans. And unlike most other jellyfish that simply ride on currents, Chironex box jellies can actively identify and swim toward prey thanks to their strong musculature and complex eyes.

Previously, scientists had mistaken C. blakangmati for another box jellyfish species, C. yamaguchii. However, it turns out that these box jellies are different, both genetically and morphologically, scientists reported in a new study, published May 15 in the journal Raffles Bulletin of Zoology.

"C. blakangmati looks remarkably like Chironex yamaguchii — a jellyfish species I first discovered in Okinawa while doing my master's degree there," study co-author Cheryl Ames, a professor of applied marine biology at Tohoku University in Japan and a research associate at the Smithsonian National Museum of Natural History in Washington, D.C., said in a statement. "But we realized they were completely distinct. I actually went back to dust off an old sample of C. yamaguchii I still had in storage in Okinawa to help with the comparisons!"

The researchers found that the newly identified species lacks branched canal structures at the bottom of its bell-shaped body that C. yamaguchii and the other two Chironex species, C. fleckeri and C. indrasaksajiae, exhibit. Specifically, these canals sit within the perradial lappets, which are flaps reinforcing the musculature that propels box jellyfish when they swim. Together with genetic discrepancies, this anatomical difference confirmed that C. blakangmati is a separate species, according to the statement.

"Our thorough review and analysis of all the Chironex species known to date reveal a lot about these box jellyfishes," study co-author Danwei Huang, an associate professor in the National University of Singapore's Department of Biological Sciences and the Lee Kong Chian Natural History Museum, said in the statement.

The results also revealed for the first time that C. indrasaksajiae, which is typically found off the coast of Thailand, is present in Singapore's waters. Nicknamed the Thai sea wasp, this species can be deadly.

"We were surprised to find C. indrasaksajiae so far away from Thailand," Ames said. "Recording range expansions like these is really important, as we currently know so little about the biodiversity and spatial distribution of box jellyfish."

A better understanding of the distribution of box jellies could help prevent severe injuries and deaths in humans, according to the statement.

Records suggest box jellyfish stings cause around 40 deaths per year globally, but some experts think that number is a huge underestimate.