Bermuda’s marine ecosystem is home to a fascinating array of creatures, from vibrant reef fish to elusive crustaceans that scuttle along the sandy seafloor. Among the lesser-known but highly intriguing inhabitants of Bermuda’s waters are box crabs, a group of cryptic and well-camouflaged crustaceans that belong to the family Calappidae. Box crabs, sometimes called shame-faced crabs due to their unique front claws that resemble hands covering a face, are specialised burrowers and ambush predators.
They possess a hard, rounded carapace that provides excellent defence against predators, and their coloration, often sandy or mottled, helps them disappear into the seabed. Some of the most common species found in Bermuda include the Flame Box Crab (Calappa flammea) and the Smooth Box Crab (Calappa gallus), both of which are well adapted to life on Bermuda’s sandy and rubble-strewn seabeds.
They are typically found in shallow waters around Bermuda, particularly in sandy or muddy substrates near coral reefs, seagrass beds, and rocky outcrops. These habitats provide the perfect cover for the crabs to burrow, where they wait for passing prey. Due to their nocturnal nature, box crabs are rarely seen by casual beachgoers or snorkelers, as they tend to remain hidden during the day and become active at night.
One of the most notable features of box crabs is their ability to fold their large claws tightly against their body, forming a near-perfect defensive shell. This adaptation not only protects them from predators such as fish and octopuses but also contributes to their “box-like” appearance. Additionally, box crabs have specially adapted hind legs that help them dig quickly into the sand when threatened. Within moments, they can bury themselves completely, rendering them nearly invisible to predators and unsuspecting divers.
Box crabs are primarily carnivorous, feeding on a diet of mollusks, small crustaceans, and carrion. They use their powerful claws to crack open the shells of bivalves such as clams and scallops, exerting immense force to extract the soft tissue inside. Their feeding strategy makes them important members of Bermuda’s marine ecosystem, as they help control populations of shellfish and recycle organic matter on the seafloor.
Little is known about the exact reproductive behaviour of box crabs in Bermuda, as they are secretive creatures. However, like many other crab species, box crabs reproduce through external fertilisation. Mating usually occurs after a female molts, at which point she becomes receptive to a male. Once fertilised, the female carries her eggs beneath her abdomen in a protective brood pouch until they hatch into free-swimming larvae. These larvae go through several planktonic stages before settling on the seabed and maturing into adults.
While box crabs are not currently considered endangered, they do face threats from habitat destruction, climate change, and human activities such as dredging and coastal development. The loss of seagrass beds and coral reef degradation in Bermuda could impact their population, as these habitats are essential for their survival.
Box crabs may not be as well-known as some of Bermuda’s more charismatic marine life, but they play an essential role in maintaining a healthy and balanced ecosystem. With their remarkable adaptations and crucial role as scavengers and predators, these intriguing crustaceans deserve greater recognition and appreciation.
