New Species of Giant Isopod Discovered in South China Sea

The new isopod species has been named Bathynomus vaderi after the most famous Sith Lord in the Star Wars movie series, Darth Vader, whose helmet resembles the marine animal’s head.

The newly-discovered species belongs to Bathynomus, the dominant scavenging isopod genus in the tropical and temperate deep sea.

First described in 1879 by the French zoologist Alphonse Milne-Edwards, this genus includes almost 20 living and four fossil species.

These creatures are abundant in the cold, deep waters of the Atlantic, Pacific and Indian Oceans.

They are well known because of their gigantism, with some species reaching large sizes in excess of 30 cm (11.8 inches) length.

They are noted for their resemblance to the much smaller common woodlouse, to which they are related.

And, just like woodlouse, although they perhaps look a little scary, they are completely harmless to humans.

“Over the last seven years, Bathynomus has become increasingly popular in Vietnam as a delicacy in contemporary culinary culture, and it has even been compared to lobsters for the quality of the flesh,” said National University of Singapore researcher Peter Ng and colleagues.

“The demand has resulted in increased fishing efforts to collect Bathynomus for the live-seafood market, and specimens have been sold alive in eateries (out of water in chilled boxes) or in cold-water tanks in large restaurants.”

“As a result of the seafood trade, we managed to obtain a large series of specimens collected by the Vietnamese fishermen in Quy Nhon City, all of which have been obtained in the South China Sea.”

“While most of the material can be referred to Bathynomus jamesi, six specimens were distinct in having a differently shaped clypeal region and pleotelson structure, with the appendix masculina distinctly shorter.”

Named Bathynomus vaderi, the new species can reach 32.5 cm (12.8 inches) in length and weigh over 1 kg.

The marine animal is known only from the waters near the Spratly Islands in Vietnam.

It is the fourth Bathynomus species with upwardly curved spines and the second supergiant in the South China Sea.

“The discovery of a species as strange as Bathynomus vaderi in Vietnam highlights just how poorly we understand the deep-sea environment,” the researchers said.

“That a species as large as this could have stayed hidden for so long reminds us just how much work we still need to do to find out what lives in Southeast Asian waters.”

“There is an urgent need to better understand our deep-sea biodiversity as humans increasingly endeavor to exploit this habitat for fisheries, oil and gas, and even minerals.”

“The sustainable fishery of giant isopods just adds to the many challenges we face. And the first step is to know what lives there.”

The team’s paper was published in the journal ZooKeys.

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P.K.L. Ng et al. 2025. A new species of supergiant Bathynomus A. Milne-Edwards, 1879 (Crustacea, Isopoda, Cirolanidae) from Vietnam, with notes on the taxonomy of Bathynomus jamesi Kou, Chen & Li, 2017. ZooKeys 1223: 289-310; doi: 10.3897/zookeys.1223.139335