Arch-Fronted Swimming Crab

Polybius navigator

The Arch-fronted Swimming Crab, known scientifically as Polybius navigator, is a small crustacean found predominantly around the British Isles and throughout the northeast Atlantic Ocean. Its range extends from the North Sea, reaching as far north as Trøndelag in Norway, and stretches southward to Mauritania. It is also present in the Mediterranean Sea. This crab species is characterized by a dark brown carapace, which can grow up to 33 millimeters wide, and lighter-colored pereiopods. A distinctive feature of the Arch-fronted Swimming Crab is the fringe of hair on the frontal margin of its carapace, positioned between the eyes, which lacks any spines. Divers are likely to encounter this species in relatively shallow waters, as 93% of occurrence records are from depths shallower than 40 meters, with most sightings at depths less than 30 meters. The Arch-fronted Swimming Crab is typically found in coastal waters and is adapted to a range of habitats within this depth range. An encounter with the Arch-fronted Swimming Crab during a dive can be an interesting experience, as these crabs are often active swimmers. However, the conservation status of this species has not been evaluated by the IUCN, leaving its population trends and potential threats uncertain.