Lago di Pilato

In a rock basin beneath the highest crest of the Sibillini, Lago di Pilato is a glacial lake at nearly 1,940 metres. When full, its two basins form a pair of spectacles. Its water shelters a coral-red fairy shrimp found nowhere else.

Why it matters

Lago di Pilato is a scientifically significant place in the Parco Nazionale dei Monti Sibillini. The park authority itself monitors the basin because one small crustacean — the chirocefalo del Marchesoni, Chirocephalus marchesonii — lives exclusively in this water, nowhere else on the planet. A glacial relic at about 1,940 metres in a hollow of the Monte Vettore massif, the lake collects snowmelt in two complementary basins that join when the water is high, giving the lake its eyeglasses shape.

What to notice

The basin lies against the eastern wall of Monte Vettore and sometimes holds snow into high summer. It is also home to Chirocephalus marchesonii, a nine-to-twelve-millimetre coral-red anostracan crustacean that swims belly-up in the cold water. Discovered in 1954 by the Camerino naturalist Vittorio Marchesoni and confirmed as a new species by Ruffo and Vesentini in 1957, it survives dry phases by leaving resistant cysts in the sediment, which stay viable for years if the lake bed is not disturbed. The species' swimming generation lives only a few months each year, between roughly June and September, synchronised with the basin's hydrological cycle.

Context and history

The lake carries a name inherited from medieval legend — the association with Pontius Pilate is the stuff of local storytelling — but its modern history is scientific. Since its discovery in the 1950s, the crustacean has made the basin a natural laboratory: the park authority ran a dedicated biological monitoring project between 28 June 2018 and 30 September 2019, executed with the University of Perugia and funded by the Ministry of the Environment with 24,459.25 euros, to assess the species' conservation status and identify risk factors and protection measures; the study also gathered data on another endemic, Chirocephalus sibyllae. The findings read as a warning. The lake's level swings hard, and in drought years it has dried completely — as in 2017. The park states plainly that climate change and hydrogeological changes, including those following seismic events, could make such complete drying more frequent and, in the medium to long term, threaten the shrimp's survival; the basin is a cold-adapted refuge whose future is tied to the mountain's climate.