How Many Legs Does a Crab Have? A Closer Look at Crab Anatomy
Crabs are fascinating creatures that inhabit oceans rivers and beaches worldwide. With their hard, protective exoskeletons and sideways scuttling, they have captured people’s imaginations for centuries. But how much do you really know about a crab’s anatomy? Specifically, how many legs does a crab have? Read on to find out.
The most common number of legs on a crab is 10. This includes 8 walking legs and 2 claws. The claws are modified legs designed for hunting, defense, and mating rituals. So while they look different than the other legs, they are still considered legs from an anatomical perspective.
Out of over 4500 crab species, the vast majority have 10 legs. However, there are a few exceptions. Porcelain crabs, for example, only have 8 legs total. They still have 2 claws like most crabs, but their walking legs number just 6 instead of the typical 8. There are even some crabs with no claws at all, like certain species of spider crabs.
So why do crabs need 10 legs? What is the function of each part? Let’s break down the anatomy:
Claws – The claws are the most noticeable part of a crab. Usually one claw is larger than the other. The bigger claw is for defense and cracking open prey, while the smaller pincer helps delicately bring food to the mouth. Claws are also used for establishing hierarchy via ritualized fights.
Walking Legs – Crabs have 4 pairs of walking legs. The first pair is closest to the mouth and usually a bit smaller than the rest. The back pair is flattened for swimming. Locomotion is achieved through a combination of steps from all the legs, giving crabs their iconic sideways scuttle.
Eye Stalks – Crabs don’t have eyes inside sockets like we do. Instead, their eyes sit on movable stalks on the top of their bodies. This allows for nearly 360 degrees of vision. The stalks can duck into slots in the shell for protection.
Antennae – Crab antennae serve both sensing and tasting purposes. Shorter antennae near the eyes help crabs identify food through touch and chemical cues. Longer, outer antennae aid navigation and detecting vibrations.
Abdomen – A crab’s abdomen is located on the underside of the main shell structure. This is a vulnerable soft area since it lacks the tough exoskeleton of the rest of the body. To protect it, crabs will tuck their abdomen safely against the body.
Carapace – The hard upper shell of a crab is called the carapace. Underneath is the gill chamber which contains respiratory structures for breathing. This hardy shell provides protection for inner organs.
Swimming Legs – The rear pair of legs are adapted for swimming, not walking. They are flattened into paddle shapes which propel the crab through water. Other legs act as rudders to steer.
Mouthparts – Hidden under the body are small mouthparts optimized for tearing and grinding food. Beyond the claws, crabs have additional modified legs near the mouth that help pass chunks of food in.
Now that we’ve explored crab anatomy in more detail, it’s clear that those 10 legs serve important survival functions. The front claws grasp prey and fend off threats. Walking legs enable that unique crab shuffle. Swimming legs propel them through water. And antennae act as critical sensors. Every leg has a purpose!
Next time you see a crab scurrying along the beach or pictured in a seafood restaurant, take a second look at its legs. Each one has an evolutionary purpose adapted over millions of years to make crabs successful survivors. Whether it’s 8 legs or 10, a crab’s anatomy is optimized through natural selection to thrive in its environment. Keep an eye out for those specialized legs the next time you spot one of these fascinating creatures.
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.
*Photo courtesy of Alaska Seafood Want the latest on recipes, deals and new releases? Sign up here!
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How Many Legs Does a Crab Really Have? Learn the Truth!
FAQ
Do crabs have 6 or 8 legs?
Does a sea crab have 10 legs?
Crabs have unusual bodies. They are decapods. This means that they have 10 limbs. The front two legs have claws, known as pincers.
What is a 10 legged crab called?
They are called ‘decapod‘ crustaceans because they have 10 limbs, this comes from the Greek word Decapoda which translates into ‘ten-footed’. While they might not be fluffy, these animals have some pretty amazing characteristics – and we believe they deserve greater protections!
Do any crabs have 12 legs?
No, crabs do not have 12 legs. All true crabs have 10 legs.