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Kidadl Team

AUGUST 05, 2021

Crab Facts You’ll Never Forget

Here are amazing crab facts about this marine arthropod.

Crabs are crustacean decapods, scientifically known as Brachyura. They are arthropods, and some species of crabs are the largest arthropods. There are more than 6,000 species of crabs belonging to approximately 93 families, including king crab, blue crab, and many more. The Japanese spider crabs are the largest crabs known to exist and have 144 in (12 ft) distance between the claws. They are followed by the Tasmanian giant crab, while the smallest crab is the pea crab which is only a millimeter long, resembling a pea. Small crab species are commonly known as sand fleas, sand bugs, sand crabs, or mole crabs.

Coconut crabs are found in areas similar to a coconut palm, and their primary source of food is coconut. Coconut crabs are known for their strong claws.

Once you are able to read and learn these crab facts, you may also want to check out giant water bug facts and cicada killer wasp facts.

Crab Interesting Facts

What type of animal is a crab?

A crab is a marine arthropod belonging to the subphylum crustaceans. They are invertebrates, lacking a backbone, but their exoskeleton protects them from predators. They walk on all four legs, moving sideways. Their claws are strong, which also helps them to hunt. They are largely consumed for their meat all over the world.  

What class of animal does a crab belong to?

A crab belongs to the class of arthropods. Some crab species, like the Japanese spider crabs, are the largest living arthropods. They can be found in multiple habitats like deep in the oceans, beaches and deserts. Some species of crabs are arboreal and are found on the barks of trees.  

How many crabs are there in the world?

There are more than 6,000 species of crabs that are found everywhere in the world and are consumed for their meat. Their conservation status as listed is Not Extinct which means that there are large populations of different crab species living in the wild.

Where does a crab live?

Crabs can be traced in all of the world’s oceans. They are also found on sandy beaches, shores, hills, forests, and even on trees. Crabs live and adapt to different habitats but are mostly found in tropical waters where the temperature is moderate.

What is a crab's habitat?

Crab species can be segregated into marine and terrestrial arthropods. Few species of crabs can live on the land for a considerably long time. Land crabs hide in dark places, and those living on beaches burrow holes in the sand to keep the water in their body from evaporation. If the gills in a crab’s body dry out, they suffer from oxygen deficiency. Some terrestrial crabs are also known to drink water from the land.

Who do crabs live with?

The behavior of the crab depends on the species it belongs to. Some species live in groups of more than 1,000 crabs which are called casts while some crabs prefer living a solitary life, and meet other crabs only during the mating period. Casts of crabs have multiple benefits, like finding a partner for mating and being safe from predators.

How long does a crab live?

The lifespan of crabs depends on their species. The blue crab is known to have a lifespan of one to eight years, while the hermit crab can live for 30 to 70 years. The horseshoe crab lives for 20 to 25 years, while the dungeness crab can survive for ten years in the wild. King crabs and red crabs also have a lifespan of 20 to 30 years, respectively. The Japanese spider crab is undoubtedly the largest known crab species and has the longest lifespan of more than 100 years.

How do they reproduce?

Crabs reproduce through copulation. The pre-mating ritual involves embracing, which continues for five to seven days. After the embracing period, the female crabs stops struggling and willingly allows the gonopods or sexual organs of the male containing sperm to slide into the female’s gonophores. The female stores the sperm in her sac until they are fertilized with the egg. The gestation period in crabs can last for more than a week, and the female crab lays more than one litter.

What is their conservation status?

The conservation status of crabs is listed as Not Extinct, considering the number of different species living in nature. Crabs are usually caught by fishermen to be sold in fish markets for consumption. All species of crabs do not have strong pincers, which makes them vulnerable to predators. They are usually shy when approached by predators and try to escape the scene.

Crab Fun Facts

What do crabs look like?

Different species of crabs have different colors. There are many colorful crabs like the orangutan crab, gulf stone crab, pebble crab, golden crab and the soft coral crab that display beautiful colors. Some crabs like the green shore crabs, fiddler crabs, and white banded crabs are known to change their colors and camouflage themselves. Some crab species are large and can weigh more than 100 lb (45 kg), while some crabs like the pea crab are pea-sized. Few crabs have strong pincers.  

A crab has two claws.

How cute are they?

Crabs are not cute, but few colorful species of crabs can be attractive in appearance. They also have a distinct quality of camouflaging themselves to defend themselves from the predator. Even though crabs are harmless, their bite can be really painful.

How do they communicate?

Crabs communicate through chemicals like pheromones. They also use the technique of stridulating which involves the crab rubbing certain body parts together to produce noise. The pre-mating ritual in crabs involves embracing the female crab. They mostly use different sounds to communicate with each other.  

How big is a crab?

The average length of a crab is 5-7 in (12-19 cm), and its average weight is 0.75-2.1 lb (0.35-0.9 kg). Some crab species can develop a body mass of 38 lb (17 kg). The Tasmanian giant crab and the Japanese spider crabs are the largest species of crabs. Pea crabs are the smallest crab species, followed by a hairy-legged hermit crab.

How fast can crabs move?

The average speed of a crab is 12 mph (19 kmph). They move in a sideways direction as they walk on all four legs. They also can walk in both forward and backward directions or in a diagonal direction. They walk sideways as they have stiff joints, and one leg never moves in the direction of the other leg.

How much does a crab weigh?

A crab can weigh between 0.75-2.1 lb (0.35-0.9 kg) depending on the species of the crab.

What are the male and female names of the species?

A male crab is called a buck, while the female is known as a jenny.

What would you call a crab?

Baby crabs are called zoea larvae.

What do they eat?

Crabs are omnivores. They eat both animal and plant material as a part of their diet. They mostly eat algae and feed on small fishes, worms, fungi, and bacteria present in the surrounding areas. Yellow land crabs climb on trees in search of food. Land crabs forage the area and hunt on seabirds, insects, fishes, or even juicy leaves and fruits.  

Are they harmful?

Some crabs are venomous in nature. A bite from a crab would not allow the poison to transfer to the human’s body as there is no mechanism in the structure of the crab to do so. Crabs can only be dangerous when they have strong pincers like the coconut crab or the red crab, which has the potential of cutting a human being's finger off. The xanthid crab is the most venomous crab, which can only poison a human being if its flesh is consumed.

Would they make a good pet?

Land crabs are difficult to be kept as pets as they tend to crawl out of their tank or vessel and usually live a shorter life span. These animals are known to live with their colonies and enjoy activities like walking, running, hunting, and even sleeping together. Red claw crabs can be kept as pets provided they have the required living conditions.

Did you know...

The sex of the crab can be confirmed by examining its underbody as the males have a phallic exterior and females have domes. A crab has an average lifespan of three to four years. The most colorful crab in the world is the sally lightfoot crab displaying a coloration of bright yellow, red, orange, blue, and white. A crab’s tooth is situated inside its stomach. If the crab loses one of its claws during a fight, it can grow it back again.

Crab meat is considered a delicacy amongst seafood lovers. This is the reason behind crabs featuring on the menu of world's leading restaurants. However, eating too much crab is bad for you because it is very high in cholesterol.

Crabs can die during molting, especially if their shells get stuck, so make sure to take extra care of your pet crabs during their molt.

How many eyes do crabs have?

Crabs have a single pair of eyes that are located on their stalk, just like snails. These animals do not have powerful eyesight but can differentiate between different colors. They can identify a moving object with the help of their eyes and detect ultraviolet light beneath the ocean.  

How do they find their new shell?

Hermit crabs find other shells belonging to snails or other animals. They infuse their body in the new shell and carry it with them. The process of molting in crabs occurs when they start developing and shed their old shell.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other arthropods including the six eyed sand spider, or a house centipede.

You can even occupy yourself at home by drawing one of our cute crab coloring pages.

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