crab, BiopicsDan BooneHonguyenseoBernard PictonBiopicsPhilippe BoujonSpletteNosferattusRushenb, CC BY-SA 4.0 , via Wikimedia Commons

Crab: Everything You need To Know

What is Crab?

Crabs are a diverse group of decapod crustaceans found in the world’s oceans, freshwater, and land. They are known for their distinctive morphology, characterized by a thick exoskeleton and a single pair of claws. This article aims to delve into the scientific study of crabs, exploring their taxonomy, physiology, ecology, behaviour, and the relationship they share with their environment and other organisms.

Taxonomy and Phylogeny

Crabs belong to the infraorder Brachyura, which houses over 6,800 species spread across 98 families as of the last update in 2021. Brachyurans are a monophyletic group, sharing a common ancestor distinct from other crustaceans. They can be further divided into several sections, such as the Dromiacea, Raninoida, Cyclodorippoida, and the Eubrachyura, which contain most known crab species.


Crabs are known for their unique body structure, with a short projecting “tail” (or telson) and a broad, laterally expanded carapace. The carapace serves as a protective shell, housing various organs. Crabs have compound eyes, stalked for better vision, and two pairs of antennae for sensory perception.

Crabs exhibit sexual dimorphism, with males often having larger claws than females. In many species, females also have a broader abdomen used to carry eggs. Like other crustaceans, crabs undergo moulting, where they shed their exoskeleton to grow.

Ecology and Behaviour

Crabs can be found in diverse habitats, ranging from the deep sea to terrestrial environments. They exhibit various behaviours for feeding, mating, and defending against predators. Many are scavengers, feeding on dead animals, while others are omnivores or predators.

Crabs are famous for their sideways locomotion, though not all crabs move this way. Some species, like the raninids, move forwards or backwards, and others can swim.

Reproduction in crabs is typically sexual, involving a distinct male and female. After mating, the female carries the fertilized eggs under her abdomen until they hatch into a larval form known as a zoea. The zoea then goes through several moults, becoming a megalopa before finally moulting into a juvenile crab.

Interactions with Humans

Crabs have significant ecological, commercial, and culinary value. They contribute to nutrient cycling in their ecosystems, and several species are fished or farmed for human consumption. However, some crab species can become invasive when introduced to new environments, damaging local biodiversity.

Climate change and ocean acidification are emerging as significant threats to crab populations. These environmental changes can affect the calcification process of crabs’ shells, impair their sensory abilities, and alter their habitats. Therefore, there’s a growing need for conservation strategies to protect crab populations and their ecosystems.

How to Cook Crab

Cooking crab is an art form, and there are countless ways to prepare it. Here are a few popular methods:

How to Boil Crab

This is one of the simplest ways to cook crab. Add your crab to a pot of boiling water, salted and seasoned with aromatic ingredients like bay leaves, lemon, and garlic. Boil the crab until it turns bright red, typically for around 10-15 minutes, depending on the size.

How to Steam Crab

Steaming is a method that can keep the crab meat tender and preserve its delicate flavour. Place the crab in a steamer basket over a pot of boiling water, cover, and steam until cooked. This usually takes about 20 minutes.

How to Grill Crab

For a smoky flavour, consider grilling your crab. You can grill a whole crab or just the legs. Brush the crab with olive oil or a marinade, then place it on a preheated grill. Cook until the shell turns red and the meat is heated, turning occasionally.

How to Roast Crab

Roasting crab in the oven can give the meat a unique, succulent flavour. Preheat your oven to 450 degrees Fahrenheit (232 degrees Celsius), place the crab in a roasting pan, add some seasoning or marinade, and roast until the crab is thoroughly heated and lightly browned.

How to Sauté Crab

Sautéing crab meat in a pan is quick and easy. Heat some oil or butter in a pan, add the crab meat and your chosen seasonings, and sauté until the crab is heated. This method is often used for crab that has already been shelled.

How to Make Crab Cakes

Crab cakes are a popular dish in many coastal regions. To make them, combine lump crab meat with breadcrumbs, mayonnaise, eggs, and your choice of seasonings, shape the mixture into patties, and fry until golden brown.

Remember, the key to cooking crab is not overcooking it, which can make the meat tough and chewy. Also, always ensure the crab is fresh and properly cleaned before cooking.


The study of crabs offers valuable insights into the complexity and diversity of life. These fascinating organisms have intricate lifecycles, diverse behaviours, and significant ecological roles. Their unique adaptations to various environments make them a compelling focus for ongoing research in marine biology, ecology, and conservation science. As scientists unravel more about crabs, they continue to enrich our understanding of the world’s biodiversity and the intricate relationships between organisms and their environments.

Crab Frequently Asked Questions

What is imitation crab? 

Imitation crab, also known as surimi, is a type of seafood made from processed fish meat, often pollock, flavoured, coloured, and shaped to resemble crab meat.

What do crabs eat? 

Crabs are omnivorous, eating both plants and animals. Their diet can include algae, mollusks, bacteria, fungi, other crustaceans, and detritus.

What do hermit crabs eat? 

Hermit crabs are also omnivores. They can consume various foods, including fruit, vegetables, meat, nuts, and commercial hermit crab food.

What is a spider crab? 

Spider crabs are a type of marine crab known for their long, spindly legs and relatively small bodies, resembling a spider.

Can dogs eat crab? 

Dogs can eat crab in moderation but must be thoroughly cooked and shelled. Crab shells can cause choking and digestive blockages.

How long do hermit crabs live? 

The lifespan of a hermit crab can vary greatly depending on the species and care provided. In captivity, they can live from 10 to 20 years with proper care.

Can you eat crab while pregnant? 

Pregnant women can eat crab, but it should be cooked thoroughly to avoid foodborne illnesses. It’s recommended to limit consumption due to concerns about mercury content.

Do crabs feel pain? 

The question of whether crabs feel pain is still debated. Some studies suggest they may feel pain, but more research is needed.

How many crabs in a bushel? 

The number of crabs in a bushel depends on the size of the crabs. For large crabs, a bushel usually holds about 60-75 crabs.

How to eat blue crab? 

Eating blue crab involves cracking the shell and picking out the meat. You can use a crab cracker or a small knife.

Is imitation crab healthy? 

Imitation crab can be a source of lean protein, but it also contains additives and is high in sodium.

Is imitation crab vegan? 

No, imitation crab is not vegan, as it’s made from fish.

What is hermit crab moulting? 

Moulting is a process in which a hermit crab sheds its exoskeleton and forms a new one, allowing it to grow.

Are crabs arachnids? 

No, crabs are crustaceans, not arachnids. They are both arthropods, but they belong to different classes.

Can dogs eat imitation crab? 

It’s not recommended, as imitation crab contains additives and high sodium levels that aren’t good for dogs.

Is crab a shellfish? 

Yes, crabs are a type of shellfish belonging to the crustacean family.

Is crab healthy to eat? 

Yes, crab is high in protein, low in fat, and a good source of vitamins and minerals, making it a healthy choice.

When is crab season? 

Crab season varies by region and species. For example, in California, Dungeness crab season usually begins in November.

Can you eat horseshoe crab? 

Horseshoe crabs are not typically eaten by humans. In some cultures, only the eggs are consumed.

Can you eat imitation crab while pregnant? 

Yes, imitation crab is typically safe for pregnant women because it’s made from fish that are low in mercury. However, it should be eaten in moderation due to its high sodium content.

Can you eat raw crab? 

Eating raw crab is not recommended due to the risk of foodborne illnesses. It’s best to cook crab thoroughly before consuming it.

How long do crabs live? 

The lifespan of crabs varies greatly by species. Some small crab species may live for a few years, while larger species, like the Alaskan king crab, can live up to 30 years.

What eats crabs? 

Crabs have many predators, including larger crabs, seabirds, fish, seals, and humans.

Where do coconut crabs live? 

Coconut crabs are found in the Indian Ocean and the central Pacific Ocean, inhabiting Seychelles and the Cook Islands.

Are horseshoe crabs dangerous?

Horseshoe crabs are not dangerous to humans. They are non-aggressive, and their tail is not venomous.

Are horseshoe crabs endangered? 

Some species of horseshoe crabs are considered endangered or vulnerable due to habitat loss and overharvesting.

What do sand crabs eat? 

Sand crabs eat detritus and plankton, which they filter from the sand using their antennae.

Can crabs swim? 

Most crabs cannot swim, but some, like the blue crab, can swim using a specialized pair of legs.

Do crabs lay eggs? 

Female crabs lay eggs, which they carry and protect until they hatch.

How do crabs reproduce? 

Crabs reproduce sexually. The male deposits sperm into the female, who then lays eggs fertilized by the stored sperm.

Is a crab a fish? 

No, crabs are not fish. They are crustaceans, which are a type of arthropod.

Is crab halal? 

According to most interpretations of Islamic dietary laws, crab is considered halal and can be eaten.

Why do crabs walk sideways? 

Most crabs walk sideways due to their legs’ structure, making sideways movement more efficient.

Can cats eat crab? 

Cats can eat small amounts of cooked crab, but it should not be a regular diet. Avoid giving cats any crab seasoning or shell.

Can you eat hermit crabs? 

Hermit crabs are not typically eaten by humans and are more commonly kept as pets.

When is blue crab season? 

Blue crab season varies by location, but it generally starts in April or May and ends in December.

Are hermit crabs nocturnal? 

Hermit crabs are primarily nocturnal, being most active at night.

Can crabs regrow limbs? 

Yes, crabs can regrow lost limbs. This process occurs during the moulting cycle.

Can hermit crabs drown? 

Yes, while hermit crabs need a humid environment and access to water, they can drown if submerged for too long.

Can you freeze imitation crab? 

Yes, you can freeze imitation crab. It’s best used within three months for optimal flavour and texture.

Do hermit crabs need a heat lamp? 

Yes, hermit crabs are tropical creatures and require a heat source to maintain a comfortable temperature.

How big can hermit crabs get? 

The size of a hermit crab depends on the species. Some may only grow a few inches, while others, like the coconut crab, can reach sizes of up to 1 meter in leg span.

How big is a coconut crab? 

Coconut crabs are the largest land-living arthropods in the world. They can weigh up to 9 pounds and measure up to 3 feet from leg to leg.

How do crabs breathe? 

Crabs have gills that allow them to extract oxygen from water. Some crabs, like land and hermit crabs, can breathe air but still need to keep their gills moist.

How do hermit crabs mate? 

Hermit crabs mate by the male depositing sperm into the female’s gonopores. The female then carries the fertilized eggs under her abdomen until they’re ready to hatch.

What do crabs taste like? 

Crab meat is often described as having a sweet, delicate flavour with a soft, moist texture.

What is lump crab meat? 

Lump crab meat refers to whole pieces of white meat from the crab’s body, often used in dishes where the crab is a standout ingredient.

When is stone crab season in Florida? 

Stone crab season in Florida runs from October 15 to May 15.

Are crabs invertebrates? 

Yes, crabs are invertebrates. They belong to the phylum Arthropoda, which includes all invertebrates with an exoskeleton, segmented body, and jointed appendages.

Can you eat sand crabs? 

Yes, sand crabs (mole crabs) are edible and often used in soups and stews.

Do hermit crabs poop? 

Yes, like all living organisms, hermit crabs excrete waste. They often do this in their shell, so it’s important to provide them with a clean environment.

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