These giant freshwater crabs might just be your new Roman Empire.
Archaeologists studying Trajan’s Forum, a historical Roman ruin site, in 2005, discovered an ancient crab species, Potamon fluviatile. The only freshwater crab species indigenous to Italy, researchers suspect that they’ve been around the region since ancient times — far before it was known for gelato and pasta.
“Rome’s underground, especially in the area of the ancient Roman Forum, is very rich in water, with many passageways and hiding places to survive,” Marco Seminara, an environmental biologist at the Sapienza University of Rome, told National Geographic.
“It doesn’t surprise me that these animals have lived there for so long.”
The collapse of the Roman Empire gave the crabs a low profile to safely maneuver through the underground sewage systems of the city, surfacing only at night to feed on animal remains and other organic matter.
Nature photographer Emanule Biggi has described the crabs as a “Wall-E of nature.” He writes:
“Its fierce temperament protects it from being disturbed by many predators like water snakes and smaller birds, and even against alien species like the Louisiana freshwater crayfish.”
However, these days, data suggests that the species may be at risk.
While researchers caught and identified about 500 crabs during the height of their studies between 2004 and 2006, rising temperatures have made them nearly impossible to find.
Despite their large size — scientists say Rome’s crabs were between 13 and 20% larger than other members of the same species — they have been able to tunnel down further in their hidden canals to remain cool, as the surface of their home becomes hotter and less humid.
Human excavations are also to blame for their dwindling population, having unearthed a network of underground canals that once protected the crabs. Now, predators like seagulls and crows have breached 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 Endangered Species.
In order to save this species — which has been around for centuries — experts say they need the funding to study them.
In 2020, the Colosseum recruited naturalists to help study and monitor diverse species living in the area between the Colosseum and Roman Forum. Seminara joined naturalist Gianluca Damiani in this mission, but the results have been far less exciting than the original discovery of the species.
In the last three years, only six new crabs have been identified, Damiani told National Geographic.
“Now they’ve gone even deeper,” Damiani said. “They’re impossible to find.”
Although scientists are not concluding that the crabs currently face extinction, they can tell the crabs’ numbers are rapidly declining.
“We’d love to study these animals because they deserve to not only be studied but also saved,” Damiani said. “This population cannot disappear.”
Damiani and his colleagues have sought permission to implement grates and signs informing people about the crabs, though the city has denied these requests.
While he blames Rome’s desire to keep the area unchanged for tourists, Seminara argues that the interest in these crabs would be a site to behold in itself.
“Their existence is certainly folklorish. It would be like finding a crab living in Central Park,” he explained to National Geographic. “This is a unique animal.”
“The fact that in the Roman Forum there is the only large freshwater crustacean that we have in Italian waters, has and will always generate a certain amazement.”
For now, the crab species — which also lives in other Mediterranean areas like Malta and the Balkan Peninsula — is protected by local and national laws. But experts believe environmental education and communication is key in 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 writes in an Instagram caption, showing his images of the crabs in their natural habitat.
“The last survivors hide among sewers and canals,” he continues, “Descending ever deeper, in an urban jungle that is rapidly changing.”
Header image courtesy of Amphipolis (CC BY-SA 2.0)
