These giant freshwater crabs could be your new Roman Empire.
Archaeologists studying Trajan’s Forum, a historic Roman ruin, in 2005 discovered an ancient type of cancer, Potamon fluviatile. The only freshwater crayfish species native to Italy, researchers suspect they have been in the region since ancient times – long before it was famous for ice cream and pasta.
“The underground of Rome, especially in the area of the ancient Roman Forum, is very rich in water, with many passages and hiding places for survival,” Marco Seminara, an environmental biologist at Rome’s Sapienza University, told National Geographic.
“It doesn’t surprise me that these animals have lived there for so long.”
The fall of the Roman Empire gave the crabs a low profile to maneuver safely through the city’s underground sewer systems, surfacing only at night to feed on animal remains and other organic matter.
Nature photographer Emanuele Bighi describes crabs as “Nature’s Wall-E”. He writes:
“Its ferocious temperament keeps it from being disturbed by many predators such as water snakes and smaller birds, and even alien species such as the Louisiana freshwater crayfish.”
These days, however, data suggests that the species may be at risk.
While the researchers caught and identified about 500 crabs during the height of their studies between 2004 and 2006, rising temperatures made them nearly impossible to find.
Despite their large size – scientists estimate the Rome crabs were between 13 and 20% larger than other members of the same species – they were able to burrow deeper into their hidden burrows to stay cool, as the surface of the home they get hotter and less humid.
Human excavations are also to blame for their dwindling populations, having exposed a network of underground canals that once protected the crabs. Now, predators such as seagulls and crows have disturbed the crabs’ habitats.
Seminara told National Geographic that these days he finds more crab body parts than live crabs. The species is also listed as “near threatened” by the IUCN Red List of Threatened Species.
To save this species, which has been around for centuries, experts say they need funding to study them.
In 2020, the Colosseum hired naturalists to help study and observe various species living in the area between the Colosseum and the Roman Forum. Seminara joined naturalist Gianluca Damiani on this mission, but the results were far less exciting than the original discovery of the species.
Only six new crabs have been identified in the past three years, Damiani told National Geographic.
“Now they’ve gone even deeper,” Damiani said. “They are impossible to find.”
Although scientists have not concluded that crabs are currently facing extinction, they can say that crab numbers are rapidly declining.
“We would like to study these animals because they deserve not only to be studied, but also to be saved,” Damiani said. “This population cannot disappear.”
Damiani and his colleagues have requested permission to put up grills and signs informing people about the crabs, although the city has denied those requests.
Although he blames Rome’s desire to keep the area untouched for tourists, Seminara argues that the interest in these crabs would be a must-see in itself.
“Their existence is certainly folklore. It would be like finding a crab living in Central Park,” he explained to National Geographic. “It’s a unique animal.”
“The fact that in the Roman Forum there is the only large freshwater crustacean we have in Italian waters has caused and will always cause a certain amount of wonder.”
For now, crab species that also live in other Mediterranean areas such as Malta and the Balkan Peninsula are protected by local and national laws. But experts believe that environmental education and communication are key to saving the crabs.
For Damiani, it starts with sharing their story.
“A few steps from the Colosseum, in the heart of Rome, extraordinary crustaceans survive,” he wrote in an Instagram caption, showing his images of the crabs in their natural habitat.
“The last survivors are hiding in sewers and drains,” he continues, “descending deeper and deeper into an urban jungle that is rapidly changing.”
Header image courtesy of Amphipolis (CC BY-SA 2.0)
