Hermit crabs are fascinating creatures that make for fun and low-maintenance pets. Their unique appearance and behaviors capture the curiosity of animal lovers worldwide. One of the most common questions people have about hermit crabs is how many legs they actually have. In this article we will take a deep dive into hermit crab anatomy and answer the question – how many legs does a hermit crab have?
An Overview of Hermit Crab Anatomy
Hermit crabs belong to the crustacean family and have an exoskeleton, antennae, compound eyes, claws, and multiple pairs of legs. Their body is divided into two main parts – the cephalothorax and the abdomen
The cephalothorax consists of the head and thorax fused together. It contains the eyes, mouthparts, antennae, claws, and four pairs of walking legs. The abdomen is soft and vulnerable, which is why hermit crabs require shells for protection.
Hermit crabs have an asymmetric appearance. They have one large claw for defense and blocking the shell opening, and one smaller claw used for feeding and grooming.
Counting a Hermit Crab’s Legs
When counting a hermit crab’s legs, it’s important to note that not all legs are visible or used for walking. Hermit crabs have a total of 10 legs, but only the front 6 pairs are easily observable
The leg pairs are:
- 1 pair of chelipeds (claws)
- 2 pairs of pereiopods (walking legs)
- 1 pair of pereiopods (walking/climbing legs)
- 1 pair of pereiopods (mobility legs)
- 1 pair of pereiopods (shell gripping legs)
- 1 pair of pereiopods (gill grooming legs)
The chelipeds are the large asymmetric pincers. Since they are modified claws rather than true legs, they are sometimes not counted in the total leg number.
The next two pairs are thick and used for walking. The third pair assists in climbing and foraging. The fourth pair is short and helps grip the shell when retracted. The fifth pair is modified for gill grooming and cleaning waste from the shell.
Why Can’t All Legs Be Observed?
Hermit crabs need to protect the vulnerable abdomen within their borrowed shell home. For this reason, the last 2 pairs of legs are small and specialized to remain inside the shell opening.
The fourth pair grips the shell tightly when the crab is retracted. The fifth pair cleans the gills and removes fecal matter while housed in the shell. Both pairs play a vital role in survival despite not being used for walking.
Additionally, counting legs can be tricky because hermit crabs periodically molt their exoskeleton. Immediately after molting, the legs are soft and folded up against the body. The leg joints harden and become functional again after a few days. During this time, counting legs accurately is difficult.
Interesting Facts About Hermit Crab Legs
Beyond basic leg count, hermit crab legs have some special features:
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The chelipeds contain small hooks for grasping food. The large claw has rounded teeth for blocking the shell hole.
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Walking legs have sensory hairs called setae to detect stimuli in the environment. This helps the crab orient itself.
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Male hermit crabs have modified pleopods (abdominal appendages) to transfer sperm packets to females during mating.
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Females have feathery pleopods adapted to carry eggs once they are fertilized.
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The last pair of legs attaches to the telson to anchor the crab in its shell when retracted.
So while hermit crabs may seem simple, their specialized leg adaptations contribute to their success as land dwelling crabs. They allow hermit crabs to protect themselves, eat, reproduce, and even hear!
Takeaway: How Many Legs Does a Hermit Crab Have?
To answer our original question – hermit crabs have a total of 10 legs. But only the 6 front pairs are easily visible and used for walking. The remaining 4 pairs are small and specialized to assist mobility while tucked in the shell.
Hermit crabs are amazing little creatures, and their legs allow them to thrive both on land and sea. The next time you encounter a hermit crab, take a closer look at how they walk, climb, and anchor themselves using these specialized appendages!
Coenobita clypeatus Land hermit crabs live close to the shoreline and must have access to both land and water. They are popular pets but do not breed in human care. Consequently, the pet trade harvests them from the wild, which is unsustainable.
A hermit crabs front half is covered with a hard exoskeleton, like that of most other crabs. Its long abdomen has a softer exoskeleton, which can adapt to fit into a spiraled snail shell. A hermit crab presses its abdomen, its fourth and fifth pairs of legs, and the appendages at the end of its abdomen (called uropods) against the shells inner wall by contracting its longitudinal muscles.
Its large, left uropod hooks to the center post of the shell. It is used for defense, holding onto tree limbs and balance. The smaller, right claw and the next pair of appendages, which also have claws, are used for collecting and passing food and water to the crabs mouth. Rough surfaces help hold the crab in the shell.
Hermit crabs have reduced gills, and their moist gill chambers have highly vascularized areas for gas exchange. They have stalked eyes with acute vision, and two pairs of antennae. They use the longer pair for feeling and the shorter, feathery pair for smelling and tasting. They also have sensory hairs that are part of the exoskeleton. They use these hairs and their antennae as vibration sensors.
Hermit crabs molt as they grow, shedding their exoskeletons and creating new, larger ones to accommodate their larger bodies. A crab molts by building up enough water pressure in its body to split its old shell. Some crabs leave their shell and bury themselves in sand to molt. Some species store water in their shell before molting and remain in the shell throughout the molt, which may take from 45 to 120 days.
You can tell that a crab is freshly molted when it has a clean, bluish color. A crab may eat its molted shell, possibly for its calcium, vitamins and minerals.
When selecting a new shell, a hermit crab follows a series of steps:
- Explore the shell visually
- Test the shell for movability
- Explore the shells surface texture
- Explore the external shape of the shell
- Test the shells opening (Is it clear? Can the hermit crab get in?)
- Check the internal size to see if it can make a snap withdrawal
- Turn the shell upside down to make sure it can right itself again
Hermit crab species come in a range of sizes, from a fraction of an inch (a few millimeters) to nearly the size of a coconut.
Many different species of land hermit crabs live in tropical areas of the Indo-Pacific region, the western Atlantic and the western Caribbean.
Land hermit crabs live close to the shoreline and must have access to both land and water. They use pools and crevices of sea water to wet their gills and the interiors of their shells, and they reproduce and spend their early stages in water. Other hermit crab species are entirely aquatic.
Hermit crabs are omnivorous scavengers. They eat whatever they find, although not the former occupants of the shells they use.
At the Smithsonians National Zoo, land hermit crabs are fed crab food and assorted fruits and vegetables.
Hermit crabs mate in seawater. Before mating, the male holds the female with one claw, and then taps or strokes her with the other or pulls her back and forth. Both crabs emerge partially from their shells, placing their stomachs together to mate.
After the eggs hatch, the larvae go through several aquatic life stages and molts. When adulthood is reached, the crabs migrate to shore for a terrestrial life.
Hermit crabs are extremely popular pets and are readily available in pet stores, particularly those with nearby access to the ocean. However, the hermit crab pet business is unsustainable. Hermit crabs do not breed in human care; they return to the ocean to breed and live out the first part of their lives. As a result, all hermit crabs purchased through pet shops come from the wild.
Land hermit crabs are also at risk of habitat loss, as the mangroves and coastal areas where they live are taken over and developed by humans.
- Choose your pets wisely, and do your research before bringing an animal home. Exotic animals don’t always make great pets. Many require special care and live for a long time. Tropical reptiles and small mammals are often traded internationally and may be victims of the illegal pet trade. Never release animals that have been kept as pets into the wild.
- Avoid single-use plastics, such as plastic bottles, bags and utensils. Choosing reusable options instead can help reduce plastic pollution.
- Protect local waterways by using fewer pesticides when caring for your garden or lawn. Using fertilizers sparingly, keeping storm drains free of litter and picking up after your pet can also improve watershed health.
- Save water by switching to low-energy appliances, fixing leaks and turning off faucets when they arent in use.
- Hermit crab species come in a range of sizes, from a fraction of an inch to nearly the size of a coconut.
- A crab may eat its molted shell, possibly for its calcium, vitamins and minerals.
- lcLeast Concern
- ntNear Threatened
- vuVulnerable
- enEndangered
- crCritically Endangered
- ewExtinct in the Wild
- exExtinct
- ddData Deficient
- neNot Evaluated
How many legs does a hermit crab typically have？
FAQ
How many legs do hermit crabs have?
Like all decapods, the hermit crab has 10 legs. The three front pairs, including its two claws, are used to move around. Its second-to-last pair of legs is used to hold on to its shell, and its last pair of legs is used to hold on to the central axis of its shell.
Do crabs have 6 or 8 legs?
How Many Legs Do Crabs Have? Crabs typically have 10 legs — one pair of pincers and four pairs of walking legs.
What to do when your hermit crab loses a leg?
Crabs drop limbs when they are stressed out. Provide him with honey, calcium and proteins. He will regrow those limbs in no time at all. I know it will be tempting to pick him up and look at him, but try not to. Just get your tank as correct as possible, and he will do better.
How many legs does a hermit crab have?
Small claw – the smaller right claw which is most often used in feeding and scooping water up to the crabs maxillipeds. Pereiopods: legs. Technically hermit crabs have 10 legs including the chelipeds. 2nd &3rd pair – walking legs used for movement.
How does a hermit crab get into a shell?
To get into the shell, the hermit crab squeezes in backwards, using its four back legs to enter the shell. The back legs have hooks that anchor the hermit crab into the shell without difficulty. The next four legs are used for walking, while the front two are its chelipeds. The chelipeds are not equal in size: one is big and other is small.
What is the anatomy of a hermit crab?
Hermit crabs’ unique anatomy is not limited to their external appearance. I’ve learned that they have several fascinating internal structures and functions as well. Unlike many other types of crabs, hermit crabs have modified gills housed in the brachial chamber, located between the 4th and 5th periopods.
Do hermit crabs lose their legs?
On occasion, hermit crabs lose their legs (including their claws), but they often grow back during subsequent molts—the process of shedding its exoskeleton as it grows larger. Loss of legs may be a consequence of stress caused by various factors, including tank conditions, fighting, and mites. Hermit crabs cannot grow additional legs as adults.
What size shell does a hermit crab need?
Small hermit crabs prefer shells with openings that are ⅜ to ½ inches. Medium-sized hermit crabs like shells with openings ranging from ½ to 1 inch. Large hermit crabs opt for shell openings ranging from 1 to 1 ⅜ inch. Aside from shell size, some hermit crab species have a preference in terms of the shell opening’s shape.
Is a hermit crab a crustacean?
A hermit crab from Costa Rica. The hermit crab is a type of crab that does not have a hard shell. They use old shells for protection. They especially like old whelk shells. When the hermit crab grows in size, it finds a larger shell. The hermit crab is a crustacean, but it is very different from other crustaceans.