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10 mind-blowing facts about crabs

The ocean floor teems with a dazzling array of strange and wonderful creatures, and crustaceans rank high on the list of marine oddities. We often envision crabs and lobsters as simple creatures known for their tasty meat and impressive pincers. But beneath those hard shells lies a world of astonishing secrets and quirky behaviors waiting to be discovered!
If you’re feeling a little crabby and looking to add to your knowledge of facts, join us as we explore 10 interesting tidbits of information about crabs that will blow your mind.

10 mind blowing facts about crabs

1. There are two different kinds of crab, true crabs and false crabs

The last common ancestor of true crabs and their false counterparts lived around 250 million years ago, and may have looked more like a lobster than a typical crab, Back then, the lineage split into two main groups: one called Brachyura, which are considered true crabs, and Anomura, or what biologists consider false crabs. True crabs have short abdomens and eight legs, there are almost 7,000 species of true crab which includes blue crabs, spider crabs and ghost crabs. While false crabs, also known as anomurans, have longer abdomens and fewer legs, this includes hermit crabs, king crabs, porcelain crabs and squat lobsters.

2. Masters of Disguise: Decorator Crabs

Have you ever seen a crab sporting a hat made of seaweed or a shell-covered backpack? Meet the decorator crabs, the ultimate masters of camouflage! These crafty crustaceans carefully select bits of sponges, seaweed, and even small rocks, attaching them to their shells with specialized hooks. They do this to become almost invisible to hungry predators like fish and octopuses, although Scientists are still studying whether this is an artistic form within the crab world. Regardless, these crabs put our creative Halloween costumes to shame!

3. Crabs can regenerate lost limbs

If a crab loses a limb in a fight or accident, it has the remarkable ability to regenerate the lost limb over time. This adaptation allows them to continue functioning effectively, even after sustaining injuries. When a crab molts, it has the ability to regenerate the lost appendage. Regeneration in adult crabs takes about one year because of the seasonal molting of adult females in fall and adult males in winter. Regenerated claws start out smaller than the original and will continue to grow through multiple molts.

4. The largest crab is the Japanese spider crab

They may look like something from a 1950s sci-fi film, but Japanese spider crabs are gentle giants. They are of the 60,000 species of crustaceans on Earth, Japanese spider crabs are the largest, spanning up to 12.5 feet from the tip of one front claw to the other and weighs on average around 40 pounds. The female Japanese spider crab can lay up to 1.5 million eggs per season. They’re also one of the world’s largest arthropods, animals with no backbone, external skeletons, and multiple-jointed appendages. In this crab’s case, those appendages are its 10 legs.

5. The pea crab is the smallest known crab

The pea crab (Pinnotheres pisum), also known as a mussel flea. This tiny animal is one of the smallest crab species a female rarely gets much larger than 12mm across and is a parasite of mussels and a few other bivalve molluscs.
Mussels are a tough nut to crack: their thick shells and lightning reflexes protect them from most small predators. But the pea crab has taken on this challenge, dedicating its life to breaching these defenses to live within the protective enclosure of the shell. As the mussel sucks in seawater, edible particles are filtered out by the gills and gathered in a mucous rope, before being passed down a conveyor belt of ciliary hairs. The pea crabs simply help themselves.

6. Crabs have a hard exoskeleton

Crabs have exoskeletons rather than endoskeletons. The hard shell covering the entire body of the crab is made of a protein called chitin. The exoskeleton protects the animal from predators while also giving their body strength and support for movement. All crabs, as well as all crustaceans, have exoskeletons.
As crabs grow, they molt their exoskeleton and form a new, larger one.

7. Crabs communicate with each other

Using their modified pincers, crabs create drumming sounds by rapidly striking their abdomens. These acoustic signals are often used for courtship rituals and territorial disputes. They drum and wave their pincers to communicate with each other, they can also be aggressive to one another as males will fight over the females and for the best hiding holes.

8. Crabs have eyes on stalks

Crabs are unique in having an omni-directional eye that enables 360-degree vision both underwater and on land. The small creature’s eyes are raised above their heads like a periscope and feature flat corneas; two features that enable this multi-directional vision that means the crab can see around it without having to move its body.
These eyes can detect movements and changes in light, helping them navigate their surroundings.
When hiding in the sand, they can even use their eyestalk as a periscope.

9. Most crabs walk sideways

Crabs can actually shuffle forwards but very slowly, they walk sideways because they are much quicker that way as their legs are attached to the sides of their bodies, and their joints bend that way.
Most crabs usually stroll on the beach by walking sideways. But crabs can also walk forward, backward and diagonally.
Because crabs have stiff, jointed legs, they move faster and easier walking sideways. Walking sideways means that one leg never moves into the path of another. So a crab is also less likely to trip over its feet. That’s important when you’re keeping track of four pairs of walking legs, plus a set of claws!
A crab walking sideways pulls itself along with one set of legs and pushes with the other. Pairs of legs on opposite sides work together to carry the crab along. But that doesn’t mean it’s a slowpoke. A ghost crab can scoot sideways 5 feet in just one second. It uses only two pairs at top speed!

10. Crabs have unique defense mechanisms

Crabs employ various defense mechanisms to protect themselves from predators. Some species have sharp spines or thorny exoskeletons, while others can release noxious chemicals or use their pincers to deliver powerful pinches. It will interest you to know that the boxer crab, also known as the pompom crab or cheerleader crab, has concocted a clever defense using tiny sea anemones as weaponry. These crabs will carry anemones in each claw and wave them to warn off predators. If the predator attacks, the anemones pack a powerful sting.
It’s a great way to keep attackers at bay, and the anemones benefit by becoming mobile and thus potentially gaining access to more food. Boxer crabs don’t exactly need anemones to survive, and sometimes they’ll use coral or sponges instead.


These 10 facts about crabs provides a little glimpse into the fantastic world of these amazing creatures. From their diverse adaptations to their fascinating behaviors, crabs continue to captivate our curiosity. So when next you spot a crab scuttling along the shore or hiding amongst the rocks, take a moment to appreciate the wonders of these extraordinary creatures.

Clement Christopher

Clement Christopher is a content writer with a passion for writing unique and compelling contents about nature that grab readers attention. For the past 4 years, he has been working with clients to write contents that not only looks great but also spur interest in nature. His knack for nature compels him to volunteer at some animal shelter and also visit some zoos. He is always looking for opportunities to write and bring a unique perspective and creative approach to every project.

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