This new species of crab was just found in a Chinese fish market

Scientists trolling through a southern China fish market have stumbled upon a new species of freshwater crab, one which upon further investigation turns out to be the lone example of a brand new genus of crab thought to have descended from an ancient lineage in the Guangdong Province.

Curiosity is the scientist’s best friend, with no better proof than this case of three researchers from the University of New South Wales, Australia, the Australian Museum, Sun Yat-sen University in China and the National Chung Hsing University in Taiwan who, upon hearing of the growing pet shop trend of adding colourful ornamental crabs to aquariums, decided to check out a freshwater crab market in South China. Once there, the team spied an unusual-looking, long-legged, brightly coloured crab with a distinctive male gonopod – a swimming appendage which in crustaceans doubles as a reproductive organ. Right away, the researchers knew this was an animal that deserved further investigation.

“The native ornamental fish dealer who sold these crabs to us eventually agreed with [first author, Chao Huang’s] request to conduct a survey at his collection site, which was in northern Guangdong,” say the study’s authors, whose work appears in the online journal Zookeys.

The team was led to Yingde City in northern Guangdong where they were able to collect other specimens of the same crustacean, which were then treated to molecular analysis and compared with 51 species from 44 different genera of the potamidae family of freshwater crabs. Their results showed that the newly named Yuebeipotamon calciatile is indeed its own genus and species of crab.

“[The phylogenetic tree] strongly indicates that Yuebeipotamon does not belong to any one of the genera included in this study, giving support to the current taxonomic treatment, i.e. it is a new genus,” say the study’s authors.

Researchers observed that Yuebeipotamon prefers hanging out in pools which form along limestone hill streams, an ever-changing habitat that might explain the crab’s long, slender legs which would help in scampering in and out of the short-lived limestone pools.

Although the study’s authors stress that more work needs to be done on Yuebeipotamon before drawing further conclusions, they speculate that the genus may be of an ancient lineage, potentially indicating that its crab ancestors that may have come to the eastern regions of China earlier than previously assumed.

Having a keen eye for detail seems to be the norm for biologists, and especially for crab hunters. Just last year, scientist David Johnson of the Marine Biological Laboratory Ecosystems Center in Maine spotted an interesting species in a salt marsh tidal creek north of Boston, Massachusetts. It turned out to be an Atlantic blue crab, Callinectes sapidus, a commercially important species which was living a good 125 km north of its native habitat.

Johnson reported his finding in the Journal of Crustacean Biology, stating that the northern migration of the blue crab can be attributed to climate change which was warming the waters of the Gulf of Maine and allowing the Atlantic blue crab to move as far north as northern Maine and even into Canada where it has been found in parts of Nova Scotia.

“Climate change is lowering the thermal barriers that kept species from moving toward the poles,” Johnson said. “Climate change presents a challenge not only for ecologists, but for fisheries managers as commercially important species shift their ranges in response to warming oceans.”

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