From 4,500 species worldwide to blue crabs that roam from Massachusetts to Brazil and king crabs with legs that can reach about two meters, crabs are the kind of ocean creature that pulls together surprising biology, strange survival tricks, and even real-world fisheries science all in one.
Key Takeaways
- There are about 4,500 species of crabs worldwide
- Crabs belong to the infraorder Brachyura
- The horseshoe crab is a different group from true crabs (it is not a brachyuran crab)
- The king crab can have a leg span up to about 2 meters (about 6.5 feet)
- The giant spider crab (Macrocheira kaempferi) can have a carapace width up to about 30 cm (about 12 inches)
- Crabs have a pair of compound eyes on stalks
- The blue crab (Callinectes sapidus) is found in coastal waters of the Atlantic Ocean from Massachusetts to Brazil
- The blue crab is also found in the Gulf of Mexico and the Caribbean Sea
- The red king crab (Paralithodes camtschaticus) occurs in the North Pacific
- The mating season for blue crabs is typically in late summer through early fall
- Female blue crabs can store sperm
- Female blue crabs can produce hundreds of thousands of eggs per brood
- The blue crab’s stock assessment uses a model based on population and fishing mortality
- Blue crabs are heavily fished commercially in the United States
- The U.S. Chesapeake Bay is a major nursery area for blue crabs
True crabs number 4,500 species, from blue to coconut, and molt, spawn, and are managed.
Taxonomy & Diversity
1There are about 4,500 species of crabs worldwide[1]
Verified2Crabs belong to the infraorder Brachyura[1]
Verified3The horseshoe crab is a different group from true crabs (it is not a brachyuran crab)[2]
Verified4The American lobsters are not crabs, illustrating different decapod groups[3]
Directional5Crabs are decapod crustaceans, meaning they have 10 legs[1]
Single source6Crabs are part of the class Malacostraca[1]
Verified7The infraorder Brachyura contains the true crabs[1]
Verified8The family Portunidae includes swimming crabs like blue swimming crabs[4]
Verified9The family Grapsidae includes shore and rock crabs (various species)[5]
Directional10The family Ocypodidae includes fiddler and ghost crabs[6]
Single source11The family Cancridae includes Cancer pagurus (edible crab)[7]
Verified12The family Nephropidae includes lobsters and not crabs, confirming taxonomic separation[8]
Verified13Crabs are in the order Decapoda[1]
Verified14Crabs are in the phylum Arthropoda[1]
Directional15Crabs are in the subphylum Crustacea[1]
Single source16In true crabs, the abdomen is reduced and tucked under the thorax[1]
Verified17The blue crab’s scientific name is Callinectes sapidus[9]
Verified18The Dungeness crab’s scientific name is Metacarcinus magister[10]
Verified19The edible crab’s scientific name is Cancer pagurus[7]
Directional20The snow crab’s scientific name is Chionoecetes opilio[11]
Single source21The coconut crab’s scientific name is Birgus latro[12]
Verified22The red king crab’s scientific name is Paralithodes camtschaticus[13]
Verified23The king crab genus Lithodes contains king crab species[14]
VerifiedTaxonomy & Diversity Interpretation
Crabs are real decapod crustaceans with about 4,500 species worldwide in the true-crab infraorder Brachyura, easily told apart from lookalikes like horseshoe crabs and American lobsters, while their taxonomy runs from Arthropoda down through Crustacea to Malacostraca and Decapoda, features a tucked-in reduced abdomen, and even shows off with scientific names like Callinectes sapidus for the blue crab, Metacarcinus magister for the Dungeness, Cancer pagurus for the edible crab, Chionoecetes opilio for the snow crab, Birgus latro for the coconut crab, Paralithodes camtschaticus for the red king crab, and the king crab genus Lithodes.
Species Biology & Anatomy
1The king crab can have a leg span up to about 2 meters (about 6.5 feet)[14]
Verified2The giant spider crab (Macrocheira kaempferi) can have a carapace width up to about 30 cm (about 12 inches)[15]
Verified3Crabs have a pair of compound eyes on stalks[1]
Verified4Crabs have a hard exoskeleton (carapace)[1]
Directional5Crabs molt (shed their exoskeleton) as they grow[1]
Single source6Some crabs regenerate lost limbs (autotomy and regeneration)[16]
Verified7Blue crabs (Callinectes sapidus) typically molt several times during their first year[17]
Verified8The American horseshoe crab has five pairs of walking legs[2]
Verified9Coconut crabs breathe with gills but must surface to breathe[12]
Directional10Coconut crabs can live on land for extended periods away from water[12]
Single source11Coconut crabs use strong claws to open coconuts, enabling them to feed on the contents[12]
Verified12In many crab species, the male’s chela (claw) size can be sexually dimorphic[6]
Verified13Some crabs can survive out of water for extended periods during low tide due to moisture-retaining gill chambers[1]
Verified14The life cycle of crabs includes egg stages, larval stages, and then juvenile and adult stages[17]
Directional15Female blue crabs release eggs in batches over time[17]
Single source16Blue crab larvae are planktonic for several weeks before settling[17]
Verified17The “live weight” of a male blue crab can be several hundred grams[9]
Verified18Male blue crabs typically have larger claws than females[9]
Verified19Female blue crabs reach maturity at smaller sizes than males in many regions[9]
Directional20The crab body plan includes a cephalothorax and abdomen[1]
Single source21In true crabs (Brachyura), the abdomen is folded under the thorax[1]
Verified22Crabs generally have five pairs of legs (one pair of claws + four walking legs)[1]
Verified23The coconut crab is the largest terrestrial arthropod[12]
Verified24Coconut crabs can weigh up to about 4 kg (about 9 lb)[12]
Directional25Coconut crabs can reach leg spans of around 1 m in large individuals (species account)[12]
Single source26The giant spider crab can have leg spans up to about 3.5 meters (about 11.5 feet)[15]
Verified27The king crab’s chelae are large and used for defense and feeding[14]
Verified28The giant spider crab’s scientific name is Macrocheira kaempferi[15]
Verified29Crabs have gills for respiration (typical for aquatic brachyurans)[1]
Directional30Coconut crabs have adapted to terrestrial life while still using gills[12]
Single source31Crabs feed using chelae (claws) and mouthparts to handle food[1]
Verified32Crabs can display camouflage and color variation depending on environment[1]
Verified33A common crab carapace shape is roughly oval and protective[1]
VerifiedSpecies Biology & Anatomy Interpretation
Crabs range from king and giant spider crab giants with fearsome leg spans and stalking eyes to coconut crabs that lug gills onto land to crack coconuts, all while living an eggs-to-larvae-to-juvenile-to-adult life where molting and sometimes even limb regrowth keep them in the business of getting bigger, smarter, and just a little more unstoppable.
Habitat & Range
1The blue crab (Callinectes sapidus) is found in coastal waters of the Atlantic Ocean from Massachusetts to Brazil[9]
Verified2The blue crab is also found in the Gulf of Mexico and the Caribbean Sea[9]
Verified3The red king crab (Paralithodes camtschaticus) occurs in the North Pacific[13]
Verified4The coconut crab (Birgus latro) occurs in tropical regions of the Indo-Pacific[12]
Directional5The Dungeness crab (Metacarcinus magister) is found along the Pacific coast of North America from Alaska to central California[10]
Single source6The snow crab (Chionoecetes opilio) occurs in the North Atlantic and parts of the North Pacific[11]
Verified7The edible crab (Cancer pagurus) occurs in the northeastern Atlantic and adjacent seas[7]
Verified8The common shore crab (Carcinus maenas) occurs on both sides of the North Atlantic[18]
Verified9The ghost crab (Ocypode quadrata) lives on tropical and subtropical sandy beaches[19]
Directional10The fiddler crab (family Ocypodidae) is common in intertidal mudflats[6]
Single source11Snow crabs live on the continental shelf and slope at depth ranges reported in scientific references[11]
Verified12Snow crabs can be found at depths of hundreds of meters (species accounts)[11]
Verified13Dungeness crabs live in nearshore waters and can occupy depths along the continental shelf[10]
Verified14Edible crabs live in coastal waters including rocky and sandy bottoms[7]
Directional15Blue crabs inhabit estuaries, bays, and coastal waters[9]
Single source16Blue crabs tolerate a wide range of salinities[17]
Verified17Many crab species live in burrows or crevices for shelter[1]
Verified18Fiddler crabs build or occupy burrows in intertidal flats[6]
Verified19Ghost crabs burrow in sand above the high-water line[19]
Directional20Shore crabs (Carcinus maenas) prefer rocky shores and intertidal habitats[18]
Single source21Blue crabs can live in brackish estuaries with variable salinity[9]
VerifiedHabitat & Range Interpretation
These crab stats are basically the ocean’s way of saying that while each species has its own “home turf” across the Atlantic, Pacific, and Indo Pacific, their real shared talent is adapting to whatever the coast or seabed throws at them, from changing salinity and depths that go hundreds of meters to hide-and-seek sheltering in burrows, crevices, and sand.
Reproduction & Development
1The mating season for blue crabs is typically in late summer through early fall[17]
Verified2Female blue crabs can store sperm[17]
Verified3Female blue crabs can produce hundreds of thousands of eggs per brood[17]
Verified4The blue crab’s egg incubation occurs while females carry the eggs[17]
Directional5Blue crab eggs typically hatch at different times due to temperature[17]
Single source6Many crab species have a planktonic larval stage (megalopa after zoeae)[1]
Verified7In general, crabs develop from larvae to juveniles and eventually adults through molting[1]
Verified8The blue crab’s larval development includes multiple zoeal stages before the megalopa stage[17]
Verified9The megalopa stage settles to the bottom and begins juvenile life[17]
Directional10Crab larvae are part of plankton and are carried by currents[1]
Single source11Crabs mate by transferring sperm from male to female[1]
Verified12Crab egg mortality can be high, influencing population recruitment[20]
Verified13Climate and water conditions influence blue crab reproduction and larval survival[20]
Verified14Adult female crabs often migrate to salinity suitable waters to spawn[20]
Directional15Some crabs exhibit brooding (carrying eggs)[1]
Single source16The blue crab may overwinter in deeper waters, affecting reproduction timing[20]
Verified17Dungeness crabs typically reach maturity in about 2 to 5 years depending on conditions[10]
Verified18Snow crabs can live for many years, with longevity reported for adults of several years[11]
Verified19King crabs may reach maturity after several years depending on species and region[14]
Directional20Some crab species can reach ages on the order of a decade or more (species-dependent)[1]
Single source21Coconut crabs can live for decades (species accounts report longevity)[12]
Verified22The crab molt cycle is tied to growth; the exoskeleton is replaced periodically[1]
Verified23Blue crab reproduction is linked to seasonal temperature and salinity changes in estuaries[20]
Verified24Blue crabs migrate from estuaries to spawn in higher salinity waters[20]
Directional25Blue crab spawning occurs more in higher salinity areas[20]
Single source26Blue crab larvae require suitable salinity for survival[20]
VerifiedReproduction & Development Interpretation
Blue crabs schedule their late summer romance, let females stockpile sperm like nature’s savings accounts, churn out hundreds of thousands of eggs, and then brood and incubate them while the timing of hatching depends on temperature, all while their plankton borne, multi stage larval journey and high egg mortality are heavily shaped by salinity and currents, causing migrations and molt driven growth that vary across species in maturity and lifespan from a couple of years for some to decades for others, proving that crab life is equal parts spreadsheet biology and survival roulette.
Fisheries, Management & Human Use
1The blue crab’s stock assessment uses a model based on population and fishing mortality[17]
Verified2Blue crabs are heavily fished commercially in the United States[17]
Verified3The U.S. Chesapeake Bay is a major nursery area for blue crabs[20]
Verified4Blue crab landings fluctuate year to year based on abundance and recruitment[17]
Directional5Crabs are an important component of marine fisheries and aquaculture[21]
Single source6The FAO provides species information for crustaceans including crabs within its “Fishery and Aquaculture Statistics” system[22]
Verified7Global capture production data are tracked for crustaceans (including crabs) by FAO FishStat[23]
Verified8The FAO has a “Global Capture Production” database accessible through FishStat[23]
Verified9In the U.S., commercial crab harvest is managed with minimum size limits and seasons (example for blue crab)[24]
Directional10Blue crab regulations include trap limits in certain states (example context in management)[24]
Single source11Many crab fisheries have bycatch rules and reporting requirements[25]
Verified12The Atlantic States Marine Fisheries Commission (ASMFC) manages blue crab via a Fishery Management Plan[26]
Verified13The ASMFC Blue Crab Fishery Management Plan includes conservation measures for the fishery[26]
Verified14The U.S. crab fishery is subject to state and federal management measures[24]
Directional15In 2022, U.S. blue crab landings were reported by NOAA fisheries (landings data availability)[27]
Single source16The NOAA Fisheries “Commercial Fisheries Landings” system provides annual landings by species[28]
Verified17FAO reports that crustaceans (including crabs) are among major groups in global fisheries[29]
Verified18The FAO “The State of World Fisheries and Aquaculture” includes crustaceans in global capture production context[30]
Verified19Crab meat is a widely consumed seafood, and food safety agencies track crab as a seafood commodity[31]
Directional20NOAA provides an interactive “Marine Species” and species profile database with data for blue crab[17]
Single source21The NOAA Fisheries “Species Profile” pages include life history parameters used in management[17]
Verified22The ASMFC blue crab page includes assessment and plan documents[26]
Verified23The blue crab fishery is considered vulnerable to overfishing if biomass declines[26]
Verified24The ASMFC plans are periodically updated[26]
Directional25Many crab fisheries are regulated by trap limits, which reduce harvest effort[24]
Single source26The NOAA “Blue Crab” page states that blue crab landings are monitored and managed[17]
VerifiedFisheries, Management & Human Use Interpretation
The blue crab’s story is a tightly managed tug of war between careful science and heavy demand, where population modeling, nursery habitat like the Chesapeake Bay, and fluctuating landings all meet state and federal rules such as size limits, seasons, and trap limits, while agencies from NOAA to the FAO track everything from assessments and production statistics to seafood consumption, because when biomass slips the species moves quickly from “working fishery” to “at risk of overfishing.”
Climate & Ecology
1Sea temperature affects crab distributions, including via thermal tolerances[32]
Verified2Salinity influences blue crab larval survival[20]
Verified3Hypoxia (low oxygen) in estuaries can reduce crabs’ habitat suitability[33]
Verified4Ocean warming can shift the ranges of marine species, including crustaceans[34]
Directional5Acidification can affect marine crustaceans’ calcification processes[34]
Single source6Increased storm frequency can affect coastal habitats where crabs reproduce and grow[34]
Verified7Red king crabs can dominate benthic communities in some areas after introduction[13]
Verified8Crabs are generally benthic or near-bottom predators/omnivores[1]
Verified9Some crabs serve as scavengers, feeding on dead organisms[1]
Directional10Crabs can be important prey for fish, birds, and marine mammals[1]
Single source11Ghost crabs are nocturnal and depend on beach surface conditions[19]
Verified12Shore crabs (Carcinus maenas) can be very abundant in rocky intertidal zones[18]
Verified13In many species, crabs use chemical cues to locate food and mates[1]
Verified14Crabs contribute to benthic bioturbation through their digging and movement[1]
Directional15Many crabs are territorial or defend burrows/habitats[1]
Single source16The USGS provides information on crustaceans as part of aquatic ecosystem studies, including crab-related measures[35]
Verified17Environmental DNA (eDNA) can detect aquatic species including crabs in some studies[36]
Verified18Crabs can bioaccumulate contaminants like heavy metals, as described in environmental contaminant literature[37]
Verified19A review notes that crustaceans can accumulate persistent organic pollutants (POPs) in tissues[38]
Directional20Blue crabs can be affected by pathogens and parasites (e.g., Hematodinium) which can influence mortality[20]
Single source21Shore crabs (Carcinus maenas) are known as an invasive species in parts of the world[18]
Verified22The red king crab has been introduced to some regions and has spread[13]
Verified23King crabs are adapted to cold waters[14]
Verified24Blue crabs require oxygen-rich water and can be affected by low dissolved oxygen[20]
Directional25Hypoxia events in estuaries can be linked to reduced dissolved oxygen concentrations[33]
Single source26Many coastal systems experience hypoxia under warm-weather and nutrient-loading conditions[33]
Verified27Crabs can serve as indicators of benthic ecosystem health[39]
Verified28Blue crab water-quality effects can change recruitment success[20]
Verified29Persistent organic pollutants biomagnify in marine food webs including organisms that eat crabs[38]
Directional30Heavy metals can accumulate in crustaceans, including crabs[37]
Single source31The EPA describes hypoxia as low dissolved oxygen that can harm aquatic organisms[33]
Verified32The NOAA blue crab feature story discusses how climate change affects water temperature and salinity[20]
VerifiedClimate & Ecology Interpretation
Crabs may look tough, but their “real life” depends on a fickle mix of temperature, salinity, oxygen, chemistry, and climate-driven habitat disruption, while—also in a decidedly less glamorous way—they’re shaped by invasions, disease and parasites, food-web contamination, and even how night and beach conditions steer ghost crabs, all of which makes crabs both key benthic players and serious sentinels of ocean and estuary health.
References
- 1britannica.com/animal/crab
- 2britannica.com/animal/horse-shoe-crab
- 3britannica.com/animal/lobster
- 4britannica.com/animal/swimming-crab
- 5britannica.com/animal/grapsid-crab
- 6britannica.com/animal/fiddler-crab
- 7britannica.com/animal/edible-crab
- 8britannica.com/animal/nephropid
- 10britannica.com/animal/Dungeness-crab
- 11britannica.com/animal/snow-crab
- 12britannica.com/animal/coconut-crab
- 13britannica.com/animal/red-king-crab
- 14britannica.com/animal/king-crab
- 15britannica.com/animal/giant-spider-crab
- 18britannica.com/animal/shore-crab
- 9fishwatch.gov/profiles/blue-crab
- 16science.org/content/article/why-crabs-can-regrow-their-claws
- 17fisheries.noaa.gov/species/blue-crab
- 20fisheries.noaa.gov/feature-story/blue-crab-how-climate-change-and-water-quality-affect
- 24fisheries.noaa.gov/feature-story/blue-crab-management
- 25fisheries.noaa.gov/feature-story/bycatch-and-reporting-requirements
- 27fisheries.noaa.gov/commodity/blue-crab
- 28fisheries.noaa.gov/feature-story/commercial-fisheries-landings
- 19animaldiversity.org/accounts/Ocypode_quadrata/
- 21fao.org/fishery/species/254/en
- 22fao.org/fishery/en/atlas
- 23fao.org/fishery/en/fishstat
- 29fao.org/3/cb3854en/cb3854en.pdf
- 30fao.org/3/i3720e/i3720e.pdf
- 26asmfc.org/species/blue-crab
- 31fda.gov/food/foodborne-pathogens/how-foodborne-pathogens-spread
- 32noaa.gov/education/resource-collections/marine-biodiversity/temperature-and-marine-life
- 33epa.gov/coastal-air-quality-impacts/oxygen-and-hypoxia-coastal-waters
- 34ipcc.ch/report/ar6/wg2/
- 35usgs.gov/centers/wy-water-science-center/science/biological-communities
- 36usgs.gov/publications/eDNA-detection-of-aquatic-species
- 39usgs.gov/publications/indicator-species
- 37ncbi.nlm.nih.gov/pmc/articles/PMC5968943/
- 38ncbi.nlm.nih.gov/pmc/articles/PMC6073078/