Freshwater crabs of the ruins of Rome

Freshwater crab Potamon fluviatile

AFP reports:

Who knew? Freshwater crabs thrive in Roman ruins

3 June 2007

ROME – Who could have guessed that throughout the rise and fall of Rome’s emperors, monarchs and politicians a lowly creature has reigned supreme in the ruins of Trajan’s mighty empire?

Potamon fluviatile, an unassuming freshwater crab, has shown superior staying power, thriving in the canals built by the Etruscans nearly 3,000 years ago, Italian zoologists say.

The ancient ruins of Trajan’s Forum in the heart of the Eternal City have provided the ideal habitat for the crustacean, which is much larger than its counterparts in lakes and rivers, Massimiliano Scalici told AFP.

The narrow canals that flow under Trajan’s Forum lead to the Cloaca Massima, the ancient Roman sewage system built in the sixth century BC initially to drain local marshes.

“Early results of a genetic analysis that we are doing show that the genes of the crabs at Trajan are very close to those of Greek freshwater crabs,” Scalici said.

“So it’s very likely that they were introduced by the Greeks 2,500 or 3,000 years ago, which means they were here even before Rome was founded in 753 BC,” he added.

While in nature the crab grows to a length of five centimetres (two inches), it is more robust in the ruins, growing to more than eight centimetres.

“Once we found a moult (shed exoskeleton) measuring 12 centimetres!” Scalici said during a tour of the site.

Gigantism is one animal response to isolation, and it is a phenomenon that requires a long time,” he noted.

The hardy crabs have also “shown extraordinary adaptation” in a habitat that “is obviously very different” from that inhabited by their cousins in nature, Scalici said.

Rome’s crabs have a longer life expectancy at 15 years instead of 10 to 12, he noted.

But for all its success, Potamon fluviatile has kept a low profile in Rome, revealing its existence only a decade ago.

It was in 1997 that Scalici and another zoology student happened on a specimen minding its own business under a stone in Trajan’s amphitheatre, part of the largest of Rome’s imperial forums, built in 113 at the territorial height of the Roman Empire.

Intrigued, a small group of researchers from the University of Rome III went to work studying the only known colony of freshwater crabs living amid the noise, pollution and humans of a large city.

“We think there are about 1,000 of them, but it’s hard to say because we can’t mark their shells, given that they shed regularly,” Scalici said.

The researchers are considering fitting specimens with microchips under their shells, but they are expensive, he added.

Scalici said the crabs have very few predators, since stray cats — a frequent sight at Roman ruins — “aren’t interested, and gulls don’t come at night because the site is lit up all the time.”

As for their diet, the omnivorous crustaceans feed on algae, insect larvae and snails, as well as the occasional cigarette butt and fast-food container, Scalici said.

The amphibious creatures burrow deep to their hideaways, sometimes reaching several metres below the ruins, leaving small mounds of dirt on the surface.

Ancient Rome: here.

Moon crabs in Singapore: here.

5 thoughts on “Freshwater crabs of the ruins of Rome

  1. Hi, I plan to write small publication about aquarium crabs for Czech Republic. Unfortunatelly, I haven´t enough photos. Could you send me any your crab photo? I would write you as author and with your web adress, if you wish, of course. Thank you for kindly understanding, if you want, contact me by e-mail, please.

    Best Regards,



  2. Pingback: New Filipino crab species, threatened by mining bosses | Dear Kitty. Some blog

  3. Pingback: Brown land crab back in Singapore after 77 years | Dear Kitty. Some blog

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