Small shell carrier of the oceans: What is a crab?

What makes a crab?

Crabs belong to the large class of crustaceans (Crustacea) and form their own order called Brachyura. Typical of crabs is their short abdomen, which is usually folded under the body - in contrast to long-tailed crustaceans such as lobsters. Their body structure is compact, almost round or square, and protected by a hard chitinous shell.

Important characteristics of a crab:

• Ten legs: Two of them are powerful claws that they use to catch prey, for defense or even for communication.
• Lateral locomotion: Due to their joint structure, most crabs move sideways faster than forwards.
• Chitinous shell: The hard shell protects against predators and injuries, but must be regularly renewed by shedding.
• Eyes on stalks: These provide a wide field of vision and help to react quickly to danger.

Habitats: Crabs conquer the world

You can find crabs almost everywhere on earth - and not just in the sea! In addition to saltwater crabs, there are also numerous species in fresh water and even on land.

Examples of habitats:

• Seas and oceans: most crabs live here, for example the well-known shore crab on European coasts.
• Mangrove swamps: Here crabs skillfully climb tree roots and live in brackish water.
• Freshwater rivers and lakes: Some crab species, such as the Chinese mitten crab, have adapted to freshwater.
• Land: The coconut crab, the largest land crab in the world, spends most of its life on land and even climbs trees!

Some species, such as the ghost crabs, manage to live both on land and in water by keeping their gills moist.

The amazing diversity of crabs

There are over 7000 known crab species - from tiny species that barely measure a centimeter to giants like the Japanese giant crab, whose leg span can be up to four meters!

Some fascinating crab species:

• Japanese giant crab (Macrocheira kaempferi): With huge claws and long legs, it is the giant among crabs.
• Blue crab (Callinectes sapidus): Famous for its tasty meat and striking blue claws.
• Edible crab (Cancer pagurus): Commonly found along European coasts, with powerful claws and a heavy carapace.
• Cleaner shrimp: Not actually a real crab, but often confused. It "cleans" fish of parasites.
• Pom-pom shrimp (Lybia spp.): These tiny crabs carry live sea anemones in their claws to defend themselves.

Crabs in everyday life and culture

Crabs are not only fascinating creatures, but also play an important role in many cultures and industries.

• In the kitchen: crabs are a popular delicacy, especially in Asia, the USA and southern Europe. Species such as the king crab are highly prized for their fine meat.
• In symbolism: In astrology, the zodiac sign Cancer stands for people born between June 22 and July 22 - inspired by the protective symbolism of the crab.
• In fairy tales and myths: crabs often appear as clever or tricky creatures that overcome obstacles or show great strength.

Surprising facts about crabs

Here are some more amazing details you may not have known:

• Crabs communicate: Many crab species drum their claws on the ground or swing their legs to attract or warn conspecifics.
• Crabs can see colors: Some species have extremely good color vision that can even detect UV light.
• Crabs are "recycling masters": As scavengers, they keep their habitats clean by eating dead animals and plant remains.
• Autotomy: When attacked, crabs can blow off a claw or a leg - a new one grows back later!
• Moulting: A crab only grows by shedding its shell and forming a new one. It is particularly vulnerable during this time.

Threats and protection

Unfortunately, crabs are threatened in many places today. Overfishing, water pollution, habitat destruction and climate change are affecting many species. Crabs are particularly sensitive to changes in the salinity and temperature of their environment.

However, there are also protective measures, such as targeted closed seasons, the establishment of marine protected areas and breeding programs for endangered species. As nature lovers, we can help by consciously consuming and supporting such initiatives.

More than just "sideways runners"

Crabs are impressive, versatile animals that have successfully adapted to a wide variety of habitats over millions of years. Their fascinating body structures, complex behavior and ecological importance make them an important part of our planet.

Now it's your turn!

Have you ever observed a crab or perhaps even had a special encounter on the beach? Share your experiences or your favorite crab facts in the comments below - I'd love to hear your stories!