Is a Lobster a Crab? Unraveling the Taxonomy and Differences Between These Crustaceans

Lobsters and crabs – two of the most popular shellfish found on seafood menus and dinner tables worldwide. Their succulent meat is prized by gourmands, yet there remains some confusion around whether these two creatures are one and the same So is a lobster actually a crab? Or are they unique crustaceans with distinct attributes?

While lobsters and crabs share similarities that lump them into the broader category of decapod crustaceans they belong to separate sub-groups and exhibit key differences in anatomy habitat, taste and more. Read on as we unravel the taxonomy behind lobsters and crabs and highlight the main distinctions between these iconic edibles from the sea.

How Lobsters and Crabs Are Classified

From a taxonomy perspective, lobsters and crabs both fall under the subphylum Crustacea, meaning they have an exoskeleton and undergo periodic molting. Here is how they are classified down to the order level:

Lobsters

Kingdom AnimaliaPhylum ArthropodaSubphylum CrustaceaClass MalacostracaOrder Decapoda

Crabs

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Decapoda

So lobsters and crabs are both part of the order Decapoda, along with other 10-legged crustaceans like shrimp and crayfish. Decapods are characterized by having five pairs of legs, with the front pair modified as pincers or claws.

Beyond the order level, lobsters and crabs diverge into different infraorders and families. Lobsters belong to the infraorder Achelata while true crabs fall under the infraorder Brachyura.

So while they share some broad taxonomy classifications, lobsters and crabs branch off into their own distinct crustacean categories. This reflects the evolutionary differences that have emerged between the two types of animals.

Key Differences Between Lobsters and Crabs

While taxonomically lobsters and crabs are separated after the order level, there are some more obvious physical and behavioral differences between the two:

Appearance

Lobsters have elongated bodies and tails along with large front claws. Crabs have a more rounded, flattened appearance and smaller claws. Crabs move sideways by paddling their rear legs, while lobsters walk forward.

Habitat

Crabs live in both freshwater and seawater habitats, including tropical beaches. Lobsters live mainly on rocky, muddy or sandy ocean bottoms. Some live in burrows.

Social Behavior

Crabs exhibit complex social interaction like communication and cooperation. Lobsters tend to be solitary and rarely interact outside of mating.

Diet

Both are omnivores, but crabs eat more plant matter like algae. Lobsters consume more animal protein like fish and mollusks.

Commercial Fisheries

Popular crabs fished commercially include blue crabs, king crabs and snow crabs. Spiny lobsters, slipper lobsters and clawed lobsters are major commercial lobster species.

Culinary Uses

Lobster meat has a slightly sweeter, more tender texture. Crab meat tends to be flakier with a mild briny flavor. Both are used in dishes like bisques, salads, and buttery rolls.

So while they share an order taxonomic classification, lobsters and crabs diverged evolutionarily to become anatomically and behaviorally distinct crustaceans. This accounts for why they are considered unique rather than one and the same.

Common Misconceptions Around Lobsters and Crabs

The unique names, appearances and attributes of lobsters versus crabs set them apart. However, there are some common misconceptions that blur the lines between the two:

Lobsters Are a Type of Crab

This is false – while lobsters and crabs are both decapod crustaceans, they belong to separate sub-groups after the order level based on evolutionary divergence. Lobsters have their own distinct taxonomic classifications and are not a subset of crabs.

King Crabs Are Actually a Type of Lobster

False again – king crabs belong to the crab infraorder Brachyura. Their name comes from their large size and claws, not any relation to lobsters. King crabs are crabs, not lobsters.

Crabs Have Hard Shells and Lobsters Have Soft Ones

In fact, both crabs and lobsters have hard external shells or exoskeletons made of calcium carbonate. Both must periodically molt their shell in order to grow. Their shell texture and composition is quite similar.

Crabs Are Sea Creatures and Lobsters Live On Land

Nope, it’s the opposite – crabs can inhabit both marine and freshwater habitats, including tropical beaches. Lobsters exclusively live in saltwater environments like oceans and reefs. Neither lives primarily on land.

So while lobsters and crabs stir up some confusion, a look at their taxonomy, anatomy and attributes clearly distinguishes them as unique crustaceans rather than one and the same.

Examples of True Crabs Versus True Lobsters

To help crystallize the differences between crabs and lobsters, let’s compare some specific examples of each:

Crab Examples:

• Blue crab – Found near Americas, named for its blue claws. Lives in brackish estuaries.

• Dungeness crab – Abundant on North American Pacific coast. Named for Dungeness, Washington where first described.

• King crab – Large crabs native to northern Pacific. Six major species including red and blue.

• Snow crab – Lives in cold, deep waters like Bering Sea. Known for their snowy white meat.

Lobster Examples:

• American lobster – The classic Maine lobster with large front claws. Heavily fished species.

• Spiny lobster – Found in warm waters globally. Lacks large claws but has spiny antennae.

• Slipper lobster – Absent claws but has a flat, slipper-shaped carapace. Lives in crevices.

• Rock lobster – Several lobster species native to Australia and New Zealand coasts.

Looking at popular true crab and lobster species highlights their unique anatomies consistent with their taxonomic classifications. This reiterates that lobsters are not crabs – and vice versa – beyond some base similarities at the crustacean level.

Can You Be Allergic to One but Not the Other?

For those with shellfish allergies, it’s important to understand if cross-reactivity exists between crabs and lobsters. The answer is yes – those allergic to one type of shellfish often react to other species too.

This is because the allergy is generally triggered not by meat, but by a carbohydrate called tropomyosin found in shellfish muscles. Tropomyosin molecules are quite similar across shellfish, so an allergic reaction can occur broadly across different species.

That said, some research indicates lobster tropomyosin has slightly different properties from crab and shrimp tropomyosin. So in rare cases, a very mild shellfish allergy sufferer may be able to eat lobster but not other shellfish. As always, consult a doctor about your particular allergies.

In most cases though, shellfish allergies cover both crabs and lobsters equally. Someone with a crab allergy should avoid lobster as well due to cross-reactivity potential. Managing shellfish allergies requires treating both crustaceans with the same precautions.

Can Different Species Interbreed?

While lobsters and crabs cannot interbreed across families, some interesting crossbreeding does occur within each group. For example, female blue crabs have been known to mate with male Dungeness crabs in the wild, producing hybrid crab offspring.

Among lobsters, the American lobster can successfully hybridize with the European lobster to yield viable offspring. So while crabs and lobsters cannot intermix, some viable hybrid pairings can occur among closer species within each family.

This again highlights that while lobsters and crabs are their own distinct crustaceans, there is diversity within each group in terms of unique species, sub-species and hybrid pairings that can arise.

Lobsters and Crabs – Cousins of the Sea

While lobsters and crabs each have unique attributes and taxonomy, they also share an underlying connection as decapod crustaceans. This “cousin” status binds them through some biological similarities while also distinguishing them as independent creatures with divergent evolutionary histories.

So a lobster is not a crab, nor vice versa. But both remain icons of the culinary world, gracing menus and dinner tables with their succulent, coveted meat. These crustacean cousins continue to tantalize and satisfy seafood lovers worldwide.