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What the sources say

Japanese Spider CrabMacrocheira kaempferi

Every figure, record and mechanism on the Japanese Spider Crab profile was written from a source, and this is the working table behind it: 55 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

Animal Diversity Web, University of Michigan

Macrocheira kaempferi. Animal Diversity Web, University of Michigan.

The page sayslegspan at up to 3.7 meters (12 feet)
The source saysRange length 3.7 (high) m 12.14 (high) ftNote: 12 feet rounded down from 12.14 ft
The page saysweight at 16 to 20 kilograms (35 to 44 pounds)
The source saysRange mass 16 to 20 kg 35.24 to 44.05 lbNote: 35/44 pounds rounded from 35.24/44.05 lb
The page saysmost often lives on the sandy and rocky bottom of the continental shelf and slope, across a depth range of 50 to 600 meters
The source saysJapanese spider crabs most often inhabit the sandy and rocky bottom of the continental shelf and slope ... Range depth 50 to 600 m
The page saysduring spawning season it spends most of its time in shallower water around 50 meters
The source saysDuring spawning season the crabs spend most of their time in shallower waters around 50 meters.
The page saysalthough the crabs move slowly, they occasionally hunt small marine invertebrates they can catch easily
The source saysAlthough they move slowly, giant crabs occasionally hunt for small marine invertebrates that they can catch easily.
The page saysThe limbs are long and poorly jointed to the body, and tend to come off to predators and nets
The source saysthe limbs are long and poorly-jointed to the body of the organism, and tend to come off due to predators and nets
The page saysone study found nearly three in four of these crabs missing at least one
The source saysOne study reported that nearly three quarters of these crabs are missing at least one limb, most often one of the first walking legs.
The page saysSpider crabs can usually survive with up to three walking legs missing, and the legs often grow back over successive molts
The source saysSpider crabs can usually survive with up to 3 walking legs missing. The walking legs often grow back during the successive molts.
The page saysMany juveniles decorate their shells with sponges, kelp or other objects to disguise themselves, as many spider crabs do
The source saysMany juveniles decorate their shells with sponges, kelp, or other objects to disguise themselves.Note: 'as many spider crabs do' from ADW: 'While nearly all spider crabs tend to decorate their carapaces with sponges and other items, M. kaempferi does it less than others'
The page saysMost adults do not, because their large size deters most predators, and although slow-moving, they use their claws against smaller predators
The source saysHowever, most adults do not because their large size deters most predators. Although slow-moving, they use their claws against smaller predators.
The page saysIt is an omnivorous scavenger that generally does not hunt, instead picking at dead and decaying animal and plant matter along the sea bed
The source saysMacrocheira kaempferi is an omnivorous scavenger. These large crustaceans generally do not hunt, but instead crawl along and pick at dead and decaying matter along the sea bed. This includes both animal and plant matter.
The page saysoccasionally hunts small marine invertebrates it can catch easily
The source saysgiant crabs occasionally hunt for small marine invertebrates that they can catch easily
The page saysMariners used to tell tales of the crab dragging sailors underwater and feasting on their flesh, but that is generally regarded as untrue
The source saysMariners used to tell tales of M. kaempferi dragging sailors underwater and feasting on their flesh. This is generally regarded as untrue
The page saysit is plausible that one would feed on the body of a sailor who had already drowned
The source saysit is certainly plausible that one of these crabs would feast upon the dead body of a sailor who had previously drowned
The page saysmost often in Sagami, Suruga and Tosa bays
The source saysThey are found most often in the Sagami, Suruga, and Tosa bays
The page saysIt occasionally eats living kelp and algae
The source saysThey occasionally eat living kelp and algae.
The page saysScavenger First, Hunter Second
The source saysThese large crustaceans generally do not hunt, but instead crawl along and pick at dead and decaying matter along the sea bed.
The page saysMost are missing a leg.
The source saysOne study reported that nearly three quarters of these crabs are missing at least one limb, most often one of the first walking legs.
The page sayspicking over the seafloor off Japan
The source sayspick at dead and decaying matter along the sea bed
The page saysMostly whatever is already dead.
The source saysThese large crustaceans generally do not hunt, but instead crawl along and pick at dead and decaying matter along the sea bed.Note: 'Mostly' carries the source's 'generally'; the living kelp and occasional hunting follow in the same answer
The page saysCamouflage as a Kid, Size as an Adult
The source saysMany juveniles decorate their shells with sponges, kelp, or other objects to disguise themselves. However, most adults do not because their large size deters most predators.
The page saysdangerLevel: Low
The source saysThere are no known adverse effects of Macrocheira kaempferi on humans. They rarely come into contact with humans, and their weak claws are fairly harmless.Note: Settles #836: Medium had no source; ADW also calls it "common in aquaria because of its gentle disposition".
The page saystags: omnivore
The source saysThese large crustaceans generally do not hunt, but instead crawl along and pick at dead and decaying matter along the sea bed. This includes both animal and plant matter.Note: Settles #836: replaces carnivore.
The page saystags: scavenger
The source saysMacrocheira kaempferi is an omnivorous scavenger.Note: Settles #836.
The page saystags: armored
The source saysThe well-calcified carapace is only around 37 centimeters longNote: Settles #836: kept; ADW also has spiny, stubby tubercles covering the carapace.
The page saysweightKg: 16
The source saysRange mass 16 to 20 kgNote: Settles #836: the name guess put it in Micro ("spider"); the whole 16 to 20 kg range is Medium.
The page sayslike a crab that can usually walk on with up to three legs missing and grow them back over its later molts
The source saysSpider crabs can usually survive with up to 3 walking legs missing. The walking legs often grow back during the successive molts.Note: vibe.reason, settled in #836 (was habitat-wrong and mechanism-free).
The page saysIt is a scavenger
The source saysMacrocheira kaempferi is an omnivorous scavenger.

Source
02

Georgia Aquarium

Japanese Spider Crab. Georgia Aquarium.

The page saysa giant crab known to grow up to twelve feet across
The source saysThe species has been known to grow up to 12 feet (3.7 m) across.
The page saysContinental Shelf and Slope off Japan (160 to 2,000 ft / 50 to 600 m)
The source saysFound at depths of 160 to 2,000 feet (50 – 600 m). Prefers to inhabit the vents and holes of the deeper parts of the ocean.
The page saysNot Evaluated
The source saysConservation Status “Not Evaluated” on the IUCN Red List.Note: Confirmed independently by aqpacific-jsc ('CONSERVATION STATUS: Not evaluated'). No Crossref DOI or GBIF Red List category exists for Macrocheira kaempferi: ran npm run audit:sources -- --search "Macrocheira kaempferi IUCN Red List assessment" (2026-09-27), no matching assessment returned; scratch/sources/japanese-spider-crab.md's own Red List section is also empty ("No assessment found").
The page saysrounded, knobbly carapace at about 37 centimeters (15 inches) across
The source saysIts body will grow to about 15 inches (37 cm) wideNote: ADW corroborates the size ("the well-calcified carapace is only around 37 centimeters long") and the texture: "Spiny and stubby tubercles (growths) cover the carapace" (knobbly).
The page saysMacrocheira kaempferi is listed as Not Evaluated on the IUCN Red List
The source saysConservation Status “Not Evaluated” on the IUCN Red List.Note: Current state: aqpacific-jsc (last updated January 22, 2026) also gives 'CONSERVATION STATUS: Not evaluated'; no GBIF/Crossref assessment found 2026-09-27.
The page saysSome are known to scrape the ocean floor for plants and algae, while others pry open the shells of mollusks
The source saysSome are known to scrape the bottom of the ocean floor for plants and algae, while others pry open the shells of mollusks.

Source
03

Aquarium of the Pacific, Online Learning Center

Giant Spider Crab. Aquarium of the Pacific, Online Learning Center.

The page saysBenthic Scavenger & Omnivore (Dead Fish, Mollusks, Algae)
The source saysGiant spider crabs are scavengers and omnivores (eating plants and animals). They eat small invertebrates like clams and mussels, algae, as well as dead fish and other leftovers.Note: Unhedged source for the terse stats label; 'Benthic' from ADW: 'pick at dead and decaying matter along the sea bed'.
The page saysknown in Japan as taka-ashi-gani, "tall legs crab"
The source saysThe Japanese name for this species is ‘taka-ashi-gani’ literally translating to “tall legs crab.”
The page saysThe Aquarium of the Pacific estimates its lifespan at 50 to 100 years, while saying its longevity is unknown
The source saysTheir longevity is unknown but these crabs are estimated to live 50-100 years.
The page sayslists its food as dead fish and other leftovers, algae, and small invertebrates like clams and mussels
The source saysThey eat small invertebrates like clams and mussels, algae, as well as dead fish and other leftovers.
The page saysThe Aquarium of the Pacific puts an adult's legspan at up to 3.7 meters (about 12 feet) and its weight at 16 to 20 kilograms (35 to 44 pounds)
The source saysRange mass: 16 to 20 kilograms (35.24 to 44.05 pounds) Range length: 3.7 meters (12.14 feet)Note: 12 feet and 35/44 pounds are rounded from 12.14 feet and 35.24/44.05 pounds
The page saysThe Aquarium of the Pacific estimates 50 to 100 years, but says their longevity is unknown
The source saysTheir longevity is unknown but these crabs are estimated to live 50-100 years.

Source
04

McClain et al. 2015

McClain et al. (2015). Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ.

The page saysLongest Legspan of Any Living Arthropod
The source saysMacrocheira kaempferi possesses the longest legspan of any arthropod and may be the heaviest extant arthropod.Note: the paper states the legspan claim flatly ("possesses the longest legspan"); the hedge "may be" attaches only to the separate, unused claim about being the heaviest arthropod by mass
The page saysthe arthropod with the longest reach on Earth
The source saysMacrocheira kaempferi possesses the longest legspan of any arthropod
The page saysa crab on display at the Sea Life centre in Scheveningen, The Hague, with a 3.7-meter span and a mass greater than 13.6 kilograms
The source saysA recent specimen on display at the Scheveningen Sea Life center in The Hague, Netherlands has a leg span of 3.7 m and mass greater than 13.6 kg.
The page saysa 3.8-meter span from Wikipedia and a 4-meter maximum from a classification of crustaceans
The source saysA classification of recent crustaceans placed the maximum legspan at 4 m (Martin & Davis, 2001). ... Wikipedia placed the maximum legspan at 3.8 m and the maximum mass at 19 kg.
The page saysA 2015 review of ocean giants found actual measurements rare
The source saysActual size measurements of M. kaemperi are rare, especially in the scientific literature.Note: 2015 is the paper's publication year (PeerJ, doi 10.7717/peerj.715); 'ocean giants' from its title
The page saysnone of those measurements can be confirmed
The source saysHowever, none of these measurements can be confirmed.Note: "these measurements" = the Martin & Davis (2001) 4 m figure and Wikipedia's 3.8 m/19 kg figures named in the preceding sentences, not the Scheveningen specimen or the Huang, Yu & Takeda (1990) measurement given afterward
The page saysBigger numbers circulate, but a 2015 review of ocean giants said none of them can be confirmed
The source saysWikipedia placed the maximum legspan at 3.8 m and the maximum mass at 19 kg. However, none of these measurements can be confirmed.Note: The FAQ's ref is aqpacific-jsc for the 3.7 m / 16-20 kg figures; this sentence states no figure beyond the paper's year, and names the review so the reader can find it (mcclain-2015 in references).
The page saysLongest Legspan, Least Confirmed Records
The source saysMacrocheira kaempferi possesses the longest legspan of any arthropodNote: 'Least Confirmed Records' paraphrases the paper's next lines: 'Actual size measurements of M. kaemperi are rare' and 'none of these measurements can be confirmed'

Source
05

Aguzzi et al. 2018

Aguzzi et al. (2018). Faunal activity rhythms influencing early community succession of an implanted whale carcass offshore Sagami Bay, Japan. Scientific Reports.

The page saysimplanted a sperm whale carcass on the continental slope off Sagami Bay, 500 meters down
The source saysan implanted sperm whale carcass in the continental slope (500 m depth) offshore Sagami Bay, Japan
The page saysfilmed it with a time-lapse camera every two hours for two and a half months
The source saysmonitored at a high frequency in a prolonged fashion (i.e. 2-h intervals for 2.5 months) with a seafloor lander equipped with a time-lapse video camera
The page sayssecond most abundant species, present in 14 percent of the observations
The source saysThe Japanese spider crab, Macrocheira kaempferi, was the second most abundant species, present in 14.0% of the observations and with 1002 individuals
The page saysthe scavengers peaked at the carcass at night, and a predatory fish peaked by day
The source saysscavengers (S. parasitica and M. kaempferi) and predators (P. gissu) alternated their occurrence (and peak densities) at the carcass, with the former group peaking during the night and the latter during the day
The page saysit kept a day-night rhythm
The source saysthe occurrence of strong 24-h day-night driven behavioral rhythms of the most abundant species
The page saysThe scavenging shows at a carcass.
The source saysscavengers (S. parasitica and M. kaempferi) and predators (P. gissu) alternated their occurrence

Source
06

Matsuda et al. 2005

Matsuda et al. (2005). Immobilization of laminin peptide in molecularly aligned chitosan by covalent bonding. Biomaterials.

The page saysscientists prepared molecularly aligned chitosan from its tendons and used it in a biomaterial for nerve regeneration
The source saysWe developed a new biomaterial effective for nerve regeneration consisting of molecularly aligned chitosan with laminin peptides bonded covalently. Molecularly aligned chitosan was prepared from crab (Macrocheira kaempferi) tendons by ethanol treatmentNote: corroborated by ADW's economic-importance section: "Because the walking legs are so long, researchers often use tendons from the legs or chelipeds." Only the abstract of this paper was readable, so the exact wording is verified against that abstract; no body-only detail is used.

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.