In the underground heart of Romeamong the millenary remains of Imperial holes and gods Trajan marketsthere is a naturalistic phenomenon as fascinating as unusual: the presence of giant crabs. It is the Potamon rivera kind of fresh water crab who for decades, perhaps for centuries, has found refuge in the drainage channels under Roman monuments.
These channels, often covered by bricks and closed to the public, constitute a ideal habitat thanks to constant presence of water and protection guaranteed by the structure itself. According to experts, these crustaceans would be present in the area at least by 80sbut their colonization can even date back toimperial era.
The area of the holes, in fact, was once subject to natural impaludeswhich could have favored their settlement since ancient times. With the passing of the centuries and progressive isolation, the crabs have developed particular morphological characteristics, first of all larger dimensions Compared to the conspecifics that live in natural environments: their carapace can measure up to 7-8 centimeters, almost double Compared to the 4-5 centimeters typical of the species.
They show up almost only at night
This gigantism is considered by scientists a consequence ofadaptation To a closed and stable environment, where selective pressure has favored certain evolutionary features. According to Bruno Cignini, professor at the University of Tor Vergata, these crabs are a The only case of urban evolution: animals that have resisted the transformations of the time, silently living with the modern city under its foundations.
Their presence, however, is visible almost exclusively at nightwhen they emerge to feed on invertebrates, algae and seeds. During the day, they take refuge in muddy lairs Or they remain hidden in the ravines, while some specimens become prey to crows and seagulls.
The most recent estimates speak of thousands of crabs currently present in the area, a number in clear growth compared to the 500 units surveyed years ago by the scholars of Roma Tre. These “Silent custodians” of the Roman imperial ruins today represent a little known but extraordinary wonder that tells another face of the eternal city: a balance between nature and history.
