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What is a Hairy Crab?

Kim Masters Evans
Kim Masters Evans

The hairy crab, or Pilumnus hirtellus, is a tiny crab that is native to the coastal waters of western and central Europe. It lives in rocky habitats or muddy sands along ocean shorelines. Much of its body and legs are covered with bristly hairs that accumulate sediment and help the crabs hide from their predators by blending in with the background.

All types of crabs have a hard exoskeleton, or external skeleton, that covers at least some parts of their bodies. A carapace is a piece of the exoskeleton that covers the head and central portion of many crabs. The hairy crab has a fan-shaped carapace that is slightly wider than it is long. This carapace typically measures around 0.8-1.2 inches (2-3 centimeters) along its width and length and appears reddish-brown or slightly purple in color.

The hairy crab lives among rocks and stones on the ocean floor.
The hairy crab lives among rocks and stones on the ocean floor.

Hairy crabs are decapods, meaning they have ten legs. Five legs extend outward from each side of the carapace. The back four legs on either side are walking legs that help the crab scuttle along. The front two legs, one on each side, are called chelipeds, and each of them is tipped with a large chelea or pincer-like claw. The right claw is almost always noticeably bigger than the left claw in hairy crabs.

The carapace and walking legs of a hairy crab are covered with bristly hairs. In fact, hairy crabs are sometimes called bristly crabs. These hairs can accumulate silt, sediment, and muddy sand from the ocean bottom or shore, and this camouflage helps the crabs blend in with the background and hide from their predators.

The species has been found in seas around Europe, from the British Isles to northern Africa, and in the Mediterranean Sea and the Black Sea. Like most ocean-based crab species, the hairy crab lives among rocks, stones or seaweed on the ocean floor or along the coastline or in sandy holes on the beach. Although it can survive in seawater hundreds of feet (dozens of meters) deep, it mostly prefers shallower waters. It eats both vegetation and meat, including seaweed, algae, worms and the carcasses of dead sea creatures.

The Pilumnidae family, of which Pilumnus hirtellus is a member, includes dozens of other species. Many of them are also informally called hairy crabs. In addition, Chinese mitten crabs, which are members of the Varunidae family are known as Shanghai hairy crabs, or hairy crabs, for short. This species is particularly famous, because the crabs are considered a delicacy in Asian cuisine.

Frequently Asked Questions

What exactly is a hairy crab?

A hairy crab, also known as the Chinese mitten crab, is a medium-sized crustacean native to the coastal estuaries of eastern Asia. It is named for its distinguishing feature: a set of furry claws that resemble mittens. These crabs are not only a culinary delicacy but also an invasive species in some regions, impacting local ecosystems.

Where can you find hairy crabs?

Hairy crabs are indigenous to the Yangtze River Delta in China but have spread to Europe and North America. They thrive in both freshwater and saltwater, adapting to a variety of habitats. Their presence outside their native range is often attributed to ballast water discharge from ships, according to environmental studies.

Why are hairy crabs considered a delicacy?

Hairy crabs are highly prized in Chinese cuisine for their sweet, rich flesh and creamy roe. They are particularly sought after during the autumn months when they are believed to be at their best. The culinary experience is enhanced by traditional preparation methods that highlight the crab's unique flavor and texture.

What impact do hairy crabs have on the environment?

As an invasive species, hairy crabs can cause significant ecological disruption. They burrow into riverbanks and levees, leading to erosion and affecting water quality. Additionally, they compete with native species for food and habitat, potentially leading to declines in local biodiversity. Their impact on ecosystems is a subject of ongoing research.

How are hairy crabs caught?

Hairy crabs are typically caught using baited traps or pots placed in their natural habitats. Fishermen target areas where crabs are known to congregate, especially during their peak season in the fall. Sustainable fishing practices are important to prevent overharvesting and to maintain the species' population levels.

Are there any conservation efforts for hairy crabs?

Conservation efforts for hairy crabs focus on managing their population in non-native regions to prevent environmental damage. In their native habitat, regulations may be in place to ensure sustainable harvesting and protect the species during breeding seasons. Research and monitoring are crucial to balance the species' economic value with ecological considerations.

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    • The hairy crab lives among rocks and stones on the ocean floor.
      By: Richard Carey
      The hairy crab lives among rocks and stones on the ocean floor.