A new giant isopod has been discovered in the deep sea in the Gulf of Mexico

Picture of Bathynomus yucatanensis. Credit: Dr. Ming-Chi Huang, Journal of Natural History

Researchers have identified a new species of Bathonimos, the famous genera of deep-sea isopods whose viral Internet fame has made them the most popular aquatic crustacean since Sebastian in “The Little Mermaid.”

There are about 20 species of living Bathonimos, a mysterious and primitive group that lives in the benthic zone of the ocean – its deepest, rarely explored in person. Isopod crustaceans They are only closely related to their famous relatives of decapods, crabs, shrimp, and lobsters.

Publish their findings in Journal of Natural Historya group of Taiwanese, Japanese and Australian researchers has revealed the newest creature on this list: B. yucatanensis, a new species measuring about 26 cm in length, about 2,500% larger than the common wood louse.

Deep-sea isopods belong to the same group that includes terrestrial isopods variously known as wood lice, pill bugs, and pollocks, which feed on decomposing matter and are likely familiar to anyone who has lifted a rock or digs around in the garden. In fact, they look exactly the same but for their exceptional size – the largest reach nearly 50 cm. And like the wood louse, although it may look a little scary, it is completely harmless to humans.

Its whimsical features and unusual proportions have spawned endless memes and a range of products that celebrate its endearing exoticism, from plush toys to phone cases.

This discovery of B. yucatanensis brings another addition to the isothermal pantheon and raises the total known species of Bathonimos in the Gulf of Mexico to three B species. giganteus was described in 1879 and B. maxeyorum was described in 2016.

It was initially thought to be a species of B. giganteus, one of the largest species of deep-sea isopods. But closer examination of the sample, which was captured in a bait-covered trap in 2017 in the Gulf of Mexico off the Yucatan Peninsula at a depth of about 600 to 800 metres, revealed a host of unique features.

The authors claim that “B. yucatanensis is morphologically distinct from both B. giganteus and B. maxeyorum.”

The individual studied was subtly different from its relatives, which was housed in the Enoshima Aquarium in Japan. “Compared to B. giganteus, B. yucatanensis has more slender body dimensions and shorter overall length…and pereopods [thoracic limbs] More slender,” the researchers note, and it also has a longer span antennae. Both types have the same pleotelson number thorns. These spines protrude from the end of the crustacean’s tail.

They added, “Bathynomus giganteus was discovered more than a century ago, and more than 1,000 specimens have been studied without any suggestion so far of a second species with the same number of pleotelsonic spines.” “Superficial examination, using only pleotelson spines, could easily misidentify B. yucatanensis specimens as B. giganteus.”

“Compared with B. maxeyorum, the most distinguishing feature is the number of pleotelson spines – 11 in B. yucatanensis versus 7 in B. maxeyorum.” The yellow-spotted color of the shell also distinguishes it from its more gray relatives.

In order to be sure, the scientists performed a molecular genetic analysis comparing B. giganteus and B. yucatanensis. “Due to the different sequences of the two genes (COI and 16S rRNA), along with differences in morphology, we identified it as a new species,” they wrote. The phylogenetic tree they created showed that B. yucatanensis is the closest relative to B. giganteus.

The authors assert that “B. giganteus is indeed the closest species to B. yucatanensis”. “This indicates that the two species likely have a common ancestor. In addition, there may also be another undiscovered species of Bathynomus spp. in the western tropical Atlantic.”

The paper also shows that the samples from the South China Sea that were identified as B. kensleyi are actually B. jamesi. B. kensleyi is restricted to the Coral Sea, off the coast of Australia.

The authors caution that “it is increasingly clear that Bathynomus species may be very similar in general appearance, and there is a long history of misidentification of species in the genus.”

They note that these differences between the newly established species have implications for keep. “Some Bathynomus species with commercial potential have become targets of deep-sea trawl fisheries,” they say. While giant isopods are exploited only sporadically, “to manage the fisheries of Panthenomus, it is important to know precisely which ones are Ocean They are arrested.”