A giant yellow crustacean in an aquarium turns out to be a new species

Bathynomus yucatanensis is one of nearly two dozen known species of giant isopods found in the deep sea.

Dr. Ming-Chih Huang, Journal of Natural History

A giant armored crustacean kept in a Japanese aquarium turned out to be a new species. The discovery adds to the nearly two dozen known species of giant isopods – large 14-legged crustaceans that relish the deepest, darkest and coldest waters of the Atlantic, Pacific and Indian oceans.

When the yellow crustacean was collected in a baited trap off Mexico’s Yucatán peninsula in 2017, it was assumed to belong to the Bathonym giganteus species of isopod and was purchased by the Enoshima Aquarium in Fujisawa, Japan. The impostor avoided being discovered until Huang Ming Chih at Tainan National University in Taiwan decided to sequence the DNA of the preserved specimen for a previous project on isopod genetics.

Huang was surprised to see substantial differences between the new isopod’s genome – its complete set of genetic instructions – and that of B. giganteus.

“At first I thought it was [genetic] contamination, so I repeated the [DNA] sequencing experiment multiple times, and the results were the same,” says Huang, who suggested he had two different species on his hands.

The new-to-science Bathonymus yucatanensis looks like an enlarged version of its smaller cousin, the woodlouse, or “woodlouse”. The isopod, which is about the size of a 2-liter beverage bottle, lives about 600 to 800 meters below sea level in the rarely explored benthic zone.

Upon closer examination, Huang and his collaborators also identified a handful of features that make B. yucatanensis unique. The specimen measures 26 centimeters from head to tail and 13 centimeters wide.

“Compared to B. giganteus, B. yucatanensis has more slender body proportions and shorter overall length than B. giganteus,” the authors write.

Extra-long antennae and a milky yellow shell also help it stand out from its grayer peers.

Despite an intimidating and prehistoric appearance, B. yucatanensis is harmless to humans and prefers to feed on dead whales and fish that settle on the seabed.

Because B. yucatanensis went unrecognized for so long, Huang suspects other giant isopods may have also been misidentified. He says he is already studying whether a similar crustacean from the South China Sea is a new species, suggesting the list of giant isopods will continue to grow.

Journal reference: natural history journal; DOI: 10.1080/00222933.2022.2086835

Learn more about these topics:

Comments are closed.