Alaskan king crabs live high up on the ocean floors and can be found in cold water places like the northern Pacific. King crabs are crustaceans and belong to the invertebrates group, or those animals without backbones. They have a unique abdomen that looks like a fan and is located below the back part of their shell. They are thought to be direct ancestors of the hermit crab. They are also sometimes referred to as stone crabs, or groundfish due to their ocean floor habitat.
Crabs are one of the most iconic creatures found in oceans and beaches around the world. With their hard shells, pincers and sideways scuttling, these crustaceans are instantly recognizable. But just how many legs do crabs have? The answer reveals some fascinating facts about their anatomy and evolution.
An Overview of Crab Legs
Crabs belong to a group of animals called decapods, which means “ten feet.” True crabs typically have five pairs of legs for a total of ten legs. These include:
- 2 pairs of walking legs
- 1 pair of swimmerets
- 1 pair of pinchers or claws
The front pair of legs has evolved into large pincers or claws used for defense hunting prey and asserting dominance. The rear pair acts as swimmerets to help crabs swim. The remaining four pairs are walking legs for mobility.
Some crab species have fewer than ten legs due to evolutionary adaptations. Porcelain crabs, for example, have just eight legs. Hermit crabs also have eight legs along with two additional claw-like appendages.
The Functions of Different Crab Legs
Each pair of crab legs serves specialized functions:
-
Pincers/claws: Used for hunting, defense, mating rituals and territorial displays. Crabs use them to catch prey, crack open shells or fight rivals.
-
Walking legs Allow crabs to move sideways on land and underwater. Also aid in burrowing on beaches. Equipped with tiny spikes for traction.
-
Swimmerets Paddle-like legs that enable swimming and mobility in water, Propels the crab gracefully underwater
-
Reduced legs: Some species have fewer fully functioning legs. But vestigial limbs may remain for reproductive functions.
Remarkable Leg Span of the Japanese Spider Crab
The Japanese spider crab possesses the longest leg span of any crab species. These massive creatures can measure 12 feet between the tips of their outstretched legs.
Despite their intimidating appearance, Japanese spider crabs are gentle giants that inhabit waters up to 1,500 feet deep. Their lengthy legs allow them to nimbly maneuver across the seabed.
Special Structures Enable Sideways Movement
A crab’s legs are positioned in a way that forces them to walk sideways. This unique gait provides important advantages:
- Allows rapid changes in direction to escape predators.
- Enables crabs to navigate uneven and rocky terrain.
- Lets crabs move in and out of tight spaces in coral reefs.
- Gives better vantage point and sensory perception of their surroundings.
Their specialized hip joints and articulated legs evolved for efficient sideways locomotion. This signature crab walk helps them survive the challenges of their habitats.
Different Leg Types in Closely Related Species
Hermit crabs and king crabs are anatomically different from true crabs:
-
Hermit crabs belong to the infraorder Anomura. They have just eight legs and two additional claw-like appendages. Their abdomen is elongated and soft, allowing them to insert it into discarded shells for protection.
-
King crabs also belong to Anomura. They have ten legs but carry their abdomens folded up under their main shell. This gives them a similar silhouette to true crabs, but their anatomy is noticeably distinct.
-
True crabs comprise the infraorder Brachyura. Their most defining feature is a short, rounded abdomen that fits tightly under the main shell.
Sexual Dimorphism in Crustaceans
Some crab species exhibit sexual dimorphism in their claws and legs:
-
Male fiddler crabs have one massively enlarged claw used for mating displays and fighting. The smaller claw is used for feeding and grooming. Females have two small, equal-sized claws.
-
Male king crabs often have differently sized claws. The larger crusher claw is used for defense and display. Their legs also play a role in transferring sperm to females.
-
In some crab species, males have longer legs relative to their body size. This allows them to dominate during mating rituals.
Importance of Leg Adaptations
The fascinating legs and claws of crabs enable their survival in perilous ocean environments. Whether used for swimming, walking, hunting, fighting or mating, each leg type serves crucial functions. Careful study of how crabs use their elaborate appendages provides insight into the remarkable diversity and evolution of crustaceans.
So next time you see a crab scuttling sideways across the beach, take a moment to appreciate the intricacy of these ten-legged wonders! Their specialized anatomy and locomotion are just two of the many traits that make crabs such successful organisms.
Sourced Straight from Sea to Table
Sourced through trusted experts and chosen for taste, texture and quality.
Flash frozen to lock in the fresh-off-the-dock taste.
Packaged with dry ice and shipped overnight directly to your door.
Simply thaw, prep, heat, and eat.
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/).
Most king crabs weigh between 6 and 10 pounds, but some can get as big as 20 pounds and have legs that are 6 feet across. Even though many of those king crabs that were over 20 pounds were caught in the early 1980s, before the Bristol Bay fishery crashed, In order to increase in size, king crabs must “molt” their shell. King crabs that are young molt a lot in their first few years, but they mold less when they are 4 to 5 years old. The weight of 10 pounds of king crab meat is equal to the number of king crab legs. 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 King crab has a merus (shoulders), 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 king crab’s body, or carapace, is usually sent to be canned, while the legs are split up and served separately.
The most preferred meat from a king crab is in the legs. Most people who like king crab say that the merus section, which is the biggest part of the crab leg, is the best part. Compared to other crabs, the king crab claws are not as notorious as the legs. People think that red king crab is the best kind of king crab because its meat is the moistest and sweetest. If your crab meat is blue, it means that the crab wasn’t cooked all the way through or wasn’t cleaned properly. 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!
How many legs does a crab have Demonstration with Pinchy Weiner’s cousin and James
How many legs does a crab have?
Well, it depends on the species. Most commonly known crabs have ten legs – four pairs of walking legs and one pair of pincers or claws. However, some species of false crabs may have fewer than ten legs. For example, a porcelain grab has eight legs. The appearance of a crab’s legs varies depending on the type of crab in question.
What parts make up the anatomy of a crab?
The following parts make up the anatomy of a crab: Claw or chela: The first pair of legs on a crab end with claws. Crabs use their claws to catch food, defend against predators and fight between themselves. Antenna: Crabs generally have two pairs of antennae, also known as feelers.
Do all crabs have claws?
No, not all crabs have claws. There are some species of crabs that don’t have claws at all. Instead, they have long, thin legs that they use to catch prey. Several species exhibit claws of different sizes. There are over 4,500 species of crabs that have been identified. They come in all shapes and sizes, and can be found in every ocean on Earth.
What are the two legs on a crab called?
The back two pairs of legs on a crab are called the walking legs. These legs are longer and thinner than the front legs and are used for walking along the ocean floor. The walking legs are covered in small spines that help the crab grip onto surfaces and climb over obstacles.