12 Types of Crabs Explained (With Pictures, Habitat & Diet)

Last updated: January 2026

Crabs are highly diverse crustaceans belonging to the order Decapoda and are found across marine, freshwater, and terrestrial ecosystems worldwide. With over 6,800 known species, crabs display remarkable variation in size, shape, behavior, and ecological function. They play critical roles in nutrient cycling, food webs, coastal stability, and even biomedical research.

This article explores 12 common and scientifically significant types of crabs, categorized by their habitat, physical traits, and behavior. Each species is described with key identification features, natural distribution, and ecological importance, making this guide useful for students, researchers, and nature enthusiasts alike.

Kingdom: Animalia
Phylum: Arthropoda
Class: Malacostraca
Order: Decapoda
Infraorder: Brachyura

Blue Crab:

The blue crab is native to the western Atlantic Ocean and the Gulf of Mexico and is easily recognized by its vivid blue claws and olive-green carapace. Its paddle-shaped fifth pair of legs makes it an excellent swimmer.

Blue crabs are opportunistic omnivores, feeding on fish, mollusks, and plant matter. Ecologically, they help regulate benthic communities, while economically they are one of the most valuable seafood species in North America.

Scientific name: Callinectes sapidus
Habitat: Estuaries, coastal waters, and lagoons
Key characteristics: Blue claws, flat swimming legs, hard carapace
Diet / behavior: Omnivorous scavenger feeding on fish, mollusks, plants
Interesting fact: The name sapidus means “savory,” reflecting its culinary value.

Hermit Crab:

Hermit crabs differ from true crabs due to their soft, asymmetrical abdomen, which requires protection inside empty mollusk shells. As they grow, hermit crabs actively search for larger shells, sometimes forming shell-exchange groups.

They inhabit marine, intertidal, and terrestrial environments, contributing to reef and shoreline ecosystems by recycling organic matter.

Scientific name: Superfamily Paguroidea
Habitat: Marine shores, coral reefs, and some terrestrial environments
Key characteristics: Soft abdomen, asymmetrical body, shell dependency
Diet / behavior: Omnivorous; frequently changes shells as it grows
Interesting fact: Groups of hermit crabs may line up to exchange shells in size order.

Snow Crab:

Snow crabs are found in the cold, deep waters of the North Atlantic and North Pacific Oceans. They are characterized by long, slender legs and a pale, white-to-light-brown exoskeleton that provides camouflage on the seafloor.

These crabs are commercially important and also serve as indicators of climate-driven changes in cold-water marine ecosystems.

Scientific name: Chionoecetes opilio
Habitat: Cold, deep waters of the North Atlantic and North Pacific
Key characteristics: Long legs, pale shell, slow movement
Diet / behavior: Carnivorous bottom feeder
Interesting fact: Snow crab populations are highly sensitive to ocean warming.

King Crab:

King crabs are among the largest crabs in the world, inhabiting the deep, cold waters of the northern Pacific Ocean, particularly around Alaska. They possess massive claws capable of crushing hard-shelled prey.

Despite their name, king crabs are anatomically closer to hermit crabs. They are apex benthic predators and a cornerstone of high-value fisheries.

Scientific name: Paralithodes spp.
Habitat: Deep, cold marine waters (especially Alaska)
Key characteristics: Enormous size, powerful claws
Diet / behavior: Predator feeding on mollusks and echinoderms
Interesting fact: King crabs evolved from hermit crab ancestors.

Spider Crab:

Spider crabs are named for their elongated legs and triangular bodies, often resembling spiders. Some species, such as the Japanese spider crab, can have a leg span exceeding one meter.

Many spider crabs practice decorative camouflage, attaching algae and sponges to their shells for protection, making them ecologically fascinating and visually striking.

Scientific name: Family Majidae
Habitat: Shallow to deep marine environments
Key characteristics: Extremely long legs, triangular body
Diet / behavior: Omnivorous scavenger
Interesting fact: Some species decorate their shells with algae for camouflage.

Coconut Crab:

The coconut crab is the largest terrestrial arthropod on Earth, found on islands across the Indian and Pacific Oceans. Unlike most crabs, adults live almost entirely on land and breathe using modified gills.

Coconut crabs are incredibly strong, capable of cracking coconuts and hard fruits. Due to overharvesting, they are considered vulnerable in several regions.

Scientific name: Birgus latro
Habitat: Tropical islands (terrestrial)
Key characteristics: Largest land arthropod, immense claw strength
Diet / behavior: Omnivorous; feeds on coconuts, fruits, carrion
Interesting fact: Can climb trees and crack coconuts open.

Dungeness Crab:

Native to the west coast of North America, the Dungeness crab is prized for its sweet, tender meat. It has a broad, smooth carapace and strong claws used for foraging and defense.

This species plays a key role in coastal benthic ecosystems and supports sustainable fisheries when properly managed.

Scientific name: Metacarcinus magister
Habitat: Coastal waters of western North America
Key characteristics: Broad carapace, strong claws
Diet / behavior: Omnivorous benthic feeder
Interesting fact: Named after Dungeness Spit in Washington State.

Fiddler Crab:

Fiddler crabs are small, semi-terrestrial crabs commonly found in mangroves, salt marshes, and tidal flats. Males possess one oversized claw used for mating displays and territorial signaling.

Their burrowing activity improves soil aeration and nutrient exchange, making them essential ecosystem engineers in coastal wetlands.

Scientific name: Uca spp.
Habitat: Mangroves, mudflats, salt marshes
Key characteristics: One oversized claw (males)
Diet / behavior: Feeds on organic matter in sediment
Interesting fact: Male claw-waving resembles playing a violin.

Red Rock Crab:

The red rock crab inhabits rocky shorelines and subtidal zones along the eastern Pacific coast. It is recognized by its deep red shell and black-tipped claws.

These crabs are hardy scavengers and predators, contributing to the balance of rocky intertidal food webs.

Scientific name: Cancer productus
Habitat: Rocky shores and subtidal zones
Key characteristics: Deep red shell, black-tipped claws
Diet / behavior: Carnivorous predator and scavenger
Interesting fact: Often confused with Dungeness crab but more aggressive.

Sally Lightfoot Crab:

Sally Lightfoot crabs are brightly colored and extremely agile, living in wave-swept intertidal zones along the western Americas and the Galápagos Islands.

Their speed allows them to evade predators and forage efficiently on algae, playing a role in controlling algal growth on rocky shores.

Scientific name: Grapsus grapsus
Habitat: Rocky intertidal zones
Key characteristics: Bright coloration, extreme agility
Diet / behavior: Primarily herbivorous
Interesting fact: Can run sideways faster than many predators can chase.

Horseshoe Crab:

Although not a true crab, the horseshoe crab is an ancient marine arthropod often referred to as a living fossil, having existed for over 450 million years.

Horseshoe crabs are ecologically vital and medically important—their blue blood is used in testing for bacterial contamination in vaccines and medical devices.

Scientific name: Limulus polyphemus
Habitat: Shallow coastal waters
Key characteristics: Horseshoe-shaped shell, long tail spine
Diet / behavior: Feeds on worms and mollusks
Interesting fact: Its blue blood is vital for medical safety testing.

Ghost Crab:

Ghost crabs inhabit sandy beaches and coastal dunes in tropical and subtropical regions. Their pale coloration provides camouflage, while their exceptional speed helps them escape predators.

They are primarily nocturnal and serve as indicators of beach ecosystem health, often affected by human disturbance and coastal development.

Scientific name: Ocypode spp.
Habitat: Sandy beaches and dunes
Key characteristics: Pale color, long legs
Diet / behavior: Nocturnal scavenger
Interesting fact: Can run at speeds over 2 m/s.

At-a-Glance: Comparison of Major Crab Types

Crab Type	Habitat	Size	Diet	Notable Feature
Blue Crab	Coastal marine & estuaries	Medium	Omnivore	Paddle-shaped swimming legs
Hermit Crab	Marine & terrestrial	Small–medium	Omnivore	Uses borrowed shells
Snow Crab	Deep cold oceans	Medium–large	Carnivore	Long, slender legs
King Crab	Deep cold oceans	Very large	Carnivore	Massive crushing claws
Spider Crab	Marine	Very large	Omnivore	Extremely long legs
Coconut Crab	Terrestrial islands	Very large	Omnivore	Strong enough to crack coconuts
Dungeness Crab	Coastal marine	Medium	Omnivore	Sweet edible meat
Fiddler Crab	Mangroves & mudflats	Small	Detritivore	One oversized claw
Red Rock Crab	Rocky shores	Medium	Carnivore	Red shell, black-tipped claws
Sally Lightfoot Crab	Intertidal rocks	Medium	Herbivore	Exceptional speed
Horseshoe Crab	Shallow marine	Large	Omnivore	Ancient “living fossil”
Ghost Crab	Sandy beaches	Small–medium	Omnivore	Extremely fast runner

To understand crabs in a broader ecological context, explore related topics on biodiversity, animal classification, and marine ecosystems. Crabs are closely linked to coastal ecosystem functioning, nutrient cycling, and trophic interactions, making them a key indicator group in marine ecology studies.