Cancer pagurus

The edible crab, known scientifically as *Cancer pagurus*, is a robust marine crustacean.

It is most famous for being a major food source in Western Europe. These crabs are characterized by a reddish-brown carapace, which is their hard upper shell. The front edge of this shell has nine rounded lobes that resemble a pie crust. They are also recognized by the black tips on their powerful claws. This species plays a vital role in the marine ecosystems of the North Atlantic and North Sea.

To understand how these crabs live, we must look at their nocturnal habits.

During the daylight hours, they hide in cracks, holes, or under rocks. At night, they emerge to hunt for food. They are predators that target various molluscs and crustaceans. For example, they eat blue mussels and several types of smaller crabs. To find food, they might stalk moving prey or dig large pits in the sand to reach buried animals.

The physical structure of the crab is highly specialized for survival. Their first pair of legs is modified into strong chelipeds, which are the claws used for grasping. The tips of these claws, called the dactylus and propodus, are black. Behind their eyes, the crab has complex mouthparts. These include three pairs of maxillipeds, maxillae, maxillules, and mandibles. A fold in the carapace also creates a branchial chamber, which is the space where their gills are located.

The life cycle of *C. pagurus* is a complex process of growth and reproduction. Mating occurs during the winter months. The male protects the female by forming a cage with his legs while she moults, or sheds her old shell. After internal fertilization, the female retreats to a pit on the sea floor. She lays between 250,000 and 3,000,000 eggs and holds them under her abdomen. She carries these eggs for up to eight months until they hatch into tiny larvae called zoea.

As the larvae grow, they transition through several stages. They first become postlarvae, known as megalopa, before becoming juveniles. In the juvenile stage, they have a large abdomen that eventually shrinks and folds under the body. These young crabs live in the intertidal zone before migrating to deeper water once they reach a certain size. Growth rates vary by sex; males grow faster than females. This is likely because females must spend much more energy on egg production.

Humans have interacted with these crabs through a massive commercial fishery. This is the largest crab fishery in Western Europe. Fishermen use baited traps called crab pots or creels to catch them. In 2007, the annual catch reached 60,000 tonnes. Much of this is caught around the coasts of Britain and Ireland. To protect the population, many regions have minimum landing sizes. These rules ensure that crabs are large enough to have reproduced before they are caught.

The history of how we name these animals began with Carl Linnaeus. In 1758, he described the species in his work *Systema Naturae*. Later, in 1810, Pierre André Latreille designated *Cancer* as the genus for this species. While the genus *Cancer* once included many different crabs, it is now limited to only eight species. Interestingly, the closest relative to the edible crab is the Jonah crab, *C. borealis, found in North America. This connection shows how closely related different species can be across vast oceans.