Crabs are a type of crustacean that live in oceans all over the world. Their distinctive body shape and sideways scuttling movement make them one of the most recognizable marine animals. But just how many legs does a crab have?
The Anatomy of a Crab
Crabs have an armored exoskeleton that protects their inner soft bodies. This hard outer shell is made up of plates called the carapace and helps crabs defend themselves from predators. Underneath the shell, crabs have a body segmented into sections. Each section has a pair of appendages attached to it.
Crabs have five pairs of legs for walking, climbing and swimming. The front-most pair of legs ends in pincers or claws used for defense, food handling and mating displays. Male fiddler crabs have one greatly enlarged claw that is used to attract females. Behind the walking legs are smaller appendages called swimmerets that aid in swimming. At the very back is a flap called the tail fan.
How Many Legs Do Crabs Have?
The defining anatomical feature of a crab is that it has five pairs of legs – a total of 10 legs The five pairs are
- 1 pair of claws (chelipeds)
- 4 pairs of walking legs (pereiopods)
Other 10-legged decapod groups include lobsters, crayfish and shrimp. These can be differentiated from true crabs in a few key ways:
- Crabs have short, reduced tails while lobsters and crayfish have longer tails.
- Shrimp have much more slender bodies compared to the wider crab body shape.
- Crabs walk sideways, unlike lobsters, crayfish and shrimp.
The 10 legs serve different functions. The front claws are used for defense, attracting mates, and handling food. The next four pairs are walking legs and allow the crab to move in their characteristic sideways motion. The back swimmerets help propel them through water.
Other Interesting Facts About Crab Legs
- Male fiddler crabs have one massively enlarged claw that can be up to 50% of their body size. They wave this major claw to attract female crabs.
- Hermit crabs don’t have 10 legs as adults because they use empty seashells for their shells. The shell protects their soft abdomen in place of a hard covering.
- Crabs periodically shed their exoskeletons in a process called molting as they grow. After molting, their bodies are soft until a new shell hardens.
- The coconut crab is the largest land crab with legs spanning up to 3.3 feet. Their claws are strong enough to crack coconuts.
- Some crab species migrate from the ocean to breed and release larvae on land. Their legs allow them to make the arduous journey.
Why Do Crabs Have 10 Legs?
Having 10 legs allows crabs to walk sideways, climb, swim, grasp food, and reproduce. Their last pair of specialized swimmerets gives them mobility in water. The multiple jointed legs and pointed tips allow them to grip surfaces like rocks to stay in place even in strong waves and currents. Their claws are great for defense, but also delicate enough for tasks like cleaning their eyestalks.
The configuration of 5 pairs of legs has evolved as the most useful and adaptable appendage arrangement for crabs to thrive in their environments. Even after 200 million years it clearly still serves them well. The next time you see a crab scuttling along take a closer look at those 10 versatile legs that define what makes a crab special.
Color, Size, and Counts
There are three types of Alaskan king crab and each is defined by its exterior color. Red king crab (paralithodes camtschaticus), considered the most popular and prized king crab for consumption around the world, has a dark reddish brown shell. They are most abundant off the shores of Alaska.Blue king crab (paralithodes platypus), with a visibly blue toned shell, live for the most part in the North Pacific Ocean. Blue king crab legs are slender and more oval shaped compared to red king crab legs. Golden king crab (lithodes aequispinus), has a dark brown shell. The smallest of the three, they weigh an average 5-8 pounds from tip to tip. They’re found from British Columbia to the Aleutian Islands and Japan (http://www.adfg.alaska.gov/).
The average weight of a king crab is 6 to 10 pounds, but some king crab can grow to more than 20 pounds with a leg span of 6 feet across. Though many of those king crabs close to 20 pounds were caught in the early 80s prior to the crash of the Bristol Bay fishery. In order to increase in size, king crabs must “molt” their shell. Juvenile king crabs molt frequently the first years of life and mold less when they reach 4-5 years of age. King crab is measured by the number of king crab legs it takes to reach 10 lbs of crab meat. A size of 6-9 would translate into “6-9 crab legs add up to 10 pounds.” Only king crab legs make up the count as claws are excluded.
The anatomy of King crab consists of shoulders, merus, legs, claws, joints, tips, spines and a carapace (or body). Unlike other crabs, king crabs have only six versus eight legs, and two claws. The body, or carapace, section of king crabs is typically sent to canners while the legs are separated and served individually.
The most preferred meat from a king crab is in the legs. Most king crab enthusiasts state that the best section is the merus section, that is, the largest section of the crab leg. Compared to other crabs, the king crab claws are not as notorious as the legs. Red king crab is regarded as the premium of king crab because its meat is the moistest and sweet. If your crab meat is bluish in color, that indicates either that the crab was under-cooked or wasnt cleaned appropriately. If it’s excessively salty, that’s a sign that the cooked crab wasn’t chilled properly prior to brine freezing.
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How Many Legs Do Crabs Have? – Beach Tour Guide
FAQ
Do crabs have 8 or 10 legs?
Crabs have 10 legs (5 pairs). They are classified as decapods, meaning “ten-footed”.
Which crab has 6 legs?
Unlike other crabs, king crabs have only six versus eight legs, and two claws. The body, or carapace, section of king crabs is typically sent to canners while the legs are separated and served individually.
Which crab has 8 legs?
Most true crabs have 10 legs (8 walking legs and 2 claws). However, some crustaceans that are often called crabs, like king crabs and porcelain crabs, have only 8 visible legs because their last pair is small and tucked away. These are not considered true crabs. King crabs, for example, have 8 legs, with the last pair often hidden, and 2 claws.
Which crab has 10 legs?
Both lobsters and crabs are known as decapod crustaceans, which means they have 10 legs. They are invertebrates that are actually closer in relation to arachnids and insects, as opposed to fish.