New giant deep-sea isopod discovered in the Gulf of Mexico

New giant deep-sea isopod discovered in Gulf of Mexico

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Image of Bathynomus yucatanensis. Image source: Dr. Mingzhi Huang, journal of natural history

Researchers have identified a new species of Bathonymus, the well-known genus of deep-sea isopods whose viral internet fame has made them the most famous aquatic crustacean since Sebastian of The Little Mermaid.


There are about 20 extant Bathonymus species, a mysterious and primitive group that inhabits the bottom-dwelling areas of the ocean—its deepest depths that few have personally explored. Isopod crustaceans are only distantly related to their better-known decapod relatives, crabs, shrimps and lobsters.

publish their findings in journal of natural historya team of researchers from Taiwan, Japan and Australia has revealed the latest creature on this list: the Yucatan termite, a new species about 26 centimeters long and 2,500 percent larger than the common psyllid.

Deep-sea isopods belong to the same group that includes terrestrial isopods called psyllids, drug bugs, and trichinella, which feed on decaying matter and anyone who lifts rocks or digs soil in a garden may be familiar with them. In fact, they look very similar, but they are quite large in size – the largest of them grows to almost 50 cm. And, like psyllids, while they may look a little scary, they are completely harmless to humans.

Their bizarre features and unusual size have spawned endless memes and a slew of products celebrating their cuteness and weirdness, from plush toys to phone cases.

This discovery of B. yucatanensis adds a new element to the isopod pantheon, bringing the total number of known Bathonymus species in the Gulf of Mexico to three – B. giganteus described in 1879 and B. maxeyorum in 2016 describe.

It was originally thought to be a variant of B. giganteus, one of the largest deep-sea isopods. But closer inspection of the specimen, which was caught in a bait trap at a depth of 600 to 800 meters near the Yucatan Peninsula in the Gulf of Mexico in 2017, revealed a set of unique features.

“B. yucatanensis is morphologically distinct from B. giganteus and B. maxeyorum,” the authors claim.

Held by the Enoshima Aquarium in Japan, the individuals studied differed slightly from their relatives. “Compared to B. giganteus, B. yucatanensis has a more slender body in proportions and a shorter overall length… [thoracic limbs] It’s more elongated,” the researchers observed. It also has longer antennae. Both species have the same number of pleotelson spines. These spines protrude from the crustacean’s tail.

“Bathynomus giganteus was discovered more than a century ago, and more than 1,000 specimens have been studied, and until now no second species with the same number of pleotelsonic spines has been found,” they added. “Superficial examination using only pleotelson spines could easily lead to specimens of B. yucatanensis being incorrectly identified as B. giganteus.”

“The speckled, cream-yellow colour of the shell further distinguishes it from its grey relatives.

To be sure, the scientists performed a molecular genetic analysis comparing B. giganteus and B. yucatanensis. “Due to the sequence differences of the two genes (COI and 16S rRNA), coupled with morphological differences, we identified it as a new species,” they wrote. The phylogenetic tree they constructed showed that B. yucatanensis is most closely related to B. giganteus.

“B. giganteus is indeed the closest species to B. yucatanensis,” the authors assert. “This suggests that the two species may share a common ancestor. In addition, there may be other undiscovered pufferfish genera in the tropical western Atlantic.”

The paper also clarifies that the specimen from the South China Sea identified as B. kensleyi is actually B. jamesi. B. kensleyi is restricted to the Coral Sea off the coast of Australia.

“It is increasingly apparent that species of Bathynomus may be very similar in overall appearance, and that there is a long history of misidentification of species in the genus,” the authors caution.

They point out that these newly established species differences have implications for conservation. “A number of Bathynomus species with commercial potential have been targeted by deep-sea trawling fisheries,” they said. While giant isopods are only exploited occasionally, “in order to manage deep-sea fisheries, it is important to know exactly what is caught.”


Study reveals first deep-sea crustacean genome


More information:
A new species of Bathynomus Milne-Edwards from the southern Gulf of Mexico, 1879 (Isopoda: Cirolanidae) journal of natural history (2022). DOI: 10.1080/00222933.2022.2086835

Courtesy of Taylor and Francis

Citation: New Giant Deep-Sea Isopod Discovered in Gulf of Mexico (August 9, 2022) Retrieved August 10, 2022 from https://phys.org/news/2022-08-giant-deep-sea-isopod -gulf-mexico Retrieve. html

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