---
title: "What the sources say about the Japanese Spider Crab | AnimalTracks.wiki"
description: "55 claims from the Japanese Spider Crab profile, each beside the words of the source that backs it."
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---

# What the sources say about the Japanese Spider Crab (*Macrocheira kaempferi*)

> 55 claims from the Japanese Spider Crab profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Japanese Spider Crab](https://animaltracks.wiki/animals/japanese-spider-crab/)

## Macrocheira kaempferi. Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Macrocheira_kaempferi/

| The page says | The source says |
| :--- | :--- |
| legspan at up to 3.7 meters (12 feet) | Range length 3.7 (high) m 12.14 (high) ft (note: 12 feet rounded down from 12.14 ft) |
| weight at 16 to 20 kilograms (35 to 44 pounds) | Range mass 16 to 20 kg 35.24 to 44.05 lb (note: 35/44 pounds rounded from 35.24/44.05 lb) |
| most often lives on the sandy and rocky bottom of the continental shelf and slope, across a depth range of 50 to 600 meters | Japanese spider crabs most often inhabit the sandy and rocky bottom of the continental shelf and slope ... Range depth 50 to 600 m |
| during spawning season it spends most of its time in shallower water around 50 meters | During spawning season the crabs spend most of their time in shallower waters around 50 meters. |
| although the crabs move slowly, they occasionally hunt small marine invertebrates they can catch easily | Although they move slowly, giant crabs occasionally hunt for small marine invertebrates that they can catch easily. |
| The limbs are long and poorly jointed to the body, and tend to come off to predators and nets | the limbs are long and poorly-jointed to the body of the organism, and tend to come off due to predators and nets |
| one study found nearly three in four of these crabs missing at least one | One study reported that nearly three quarters of these crabs are missing at least one limb, most often one of the first walking legs. |
| Spider crabs can usually survive with up to three walking legs missing, and the legs often grow back over successive molts | Spider crabs can usually survive with up to 3 walking legs missing. The walking legs often grow back during the successive molts. |
| Many juveniles decorate their shells with sponges, kelp or other objects to disguise themselves, as many spider crabs do | Many 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') |
| Most adults do not, because their large size deters most predators, and although slow-moving, they use their claws against smaller predators | However, most adults do not because their large size deters most predators. Although slow-moving, they use their claws against smaller predators. |
| It is an omnivorous scavenger that generally does not hunt, instead picking at dead and decaying animal and plant matter along the sea bed | Macrocheira 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. |
| occasionally hunts small marine invertebrates it can catch easily | giant crabs occasionally hunt for small marine invertebrates that they can catch easily |
| Mariners used to tell tales of the crab dragging sailors underwater and feasting on their flesh, but that is generally regarded as untrue | Mariners used to tell tales of M. kaempferi dragging sailors underwater and feasting on their flesh. This is generally regarded as untrue |
| it is plausible that one would feed on the body of a sailor who had already drowned | it is certainly plausible that one of these crabs would feast upon the dead body of a sailor who had previously drowned |
| most often in Sagami, Suruga and Tosa bays | They are found most often in the Sagami, Suruga, and Tosa bays |
| It occasionally eats living kelp and algae | They occasionally eat living kelp and algae. |
| Scavenger First, Hunter Second | These large crustaceans generally do not hunt, but instead crawl along and pick at dead and decaying matter along the sea bed. |
| Most are missing a leg. | One study reported that nearly three quarters of these crabs are missing at least one limb, most often one of the first walking legs. |
| picking over the seafloor off Japan | pick at dead and decaying matter along the sea bed |
| Mostly whatever is already dead. | These 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) |
| Camouflage as a Kid, Size as an Adult | Many 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. |
| dangerLevel: Low | There 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".) |
| tags: omnivore | 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. (note: Settles #836: replaces carnivore.) |
| tags: scavenger | Macrocheira kaempferi is an omnivorous scavenger. (note: Settles #836.) |
| tags: armored | The well-calcified carapace is only around 37 centimeters long (note: Settles #836: kept; ADW also has spiny, stubby tubercles covering the carapace.) |
| weightKg: 16 | Range mass 16 to 20 kg (note: Settles #836: the name guess put it in Micro ("spider"); the whole 16 to 20 kg range is Medium.) |
| like a crab that can usually walk on with up to three legs missing and grow them back over its later molts | Spider 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).) |
| It is a scavenger | Macrocheira kaempferi is an omnivorous scavenger. |

## Japanese Spider Crab. Georgia Aquarium.

https://www.georgiaaquarium.org/animal/japanese-spider-crab/

| The page says | The source says |
| :--- | :--- |
| a giant crab known to grow up to twelve feet across | The species has been known to grow up to 12 feet (3.7 m) across. |
| Continental Shelf and Slope off Japan (160 to 2,000 ft / 50 to 600 m) | Found 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. |
| Not Evaluated | Conservation 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").) |
| rounded, knobbly carapace at about 37 centimeters (15 inches) across | Its body will grow to about 15 inches (37 cm) wide (note: 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).) |
| Macrocheira kaempferi is listed as Not Evaluated on the IUCN Red List | Conservation 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.) |
| Some are known to scrape the ocean floor for plants and algae, while others pry open the shells of mollusks | Some are known to scrape the bottom of the ocean floor for plants and algae, while others pry open the shells of mollusks. |

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

https://www.aquariumofpacific.org/onlinelearningcenter/species/giant_spider_crab

| The page says | The source says |
| :--- | :--- |
| Benthic Scavenger & Omnivore (Dead Fish, Mollusks, Algae) | Giant 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'.) |
| known in Japan as taka-ashi-gani, "tall legs crab" | The Japanese name for this species is ‘taka-ashi-gani’ literally translating to “tall legs crab.” |
| The Aquarium of the Pacific estimates its lifespan at 50 to 100 years, while saying its longevity is unknown | Their longevity is unknown but these crabs are estimated to live 50-100 years. |
| lists its food as dead fish and other leftovers, algae, and small invertebrates like clams and mussels | They eat small invertebrates like clams and mussels, algae, as well as dead fish and other leftovers. |
| The 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) | Range 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 Aquarium of the Pacific estimates 50 to 100 years, but says their longevity is unknown | Their longevity is unknown but these crabs are estimated to live 50-100 years. |

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

https://doi.org/10.7717/peerj.715

| The page says | The source says |
| :--- | :--- |
| Longest Legspan of Any Living Arthropod | Macrocheira 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 arthropod with the longest reach on Earth | Macrocheira kaempferi possesses the longest legspan of any arthropod |
| a 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 | A 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. |
| a 3.8-meter span from Wikipedia and a 4-meter maximum from a classification of crustaceans | A 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. |
| A 2015 review of ocean giants found actual measurements rare | Actual 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) |
| none of those measurements can be confirmed | However, 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) |
| Bigger numbers circulate, but a 2015 review of ocean giants said none of them can be confirmed | Wikipedia 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).) |
| Longest Legspan, Least Confirmed Records | Macrocheira kaempferi possesses the longest legspan of any arthropod (note: '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') |

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

https://doi.org/10.1038/s41598-018-29431-5

| The page says | The source says |
| :--- | :--- |
| implanted a sperm whale carcass on the continental slope off Sagami Bay, 500 meters down | an implanted sperm whale carcass in the continental slope (500 m depth) offshore Sagami Bay, Japan |
| filmed it with a time-lapse camera every two hours for two and a half months | monitored 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 |
| second most abundant species, present in 14 percent of the observations | The Japanese spider crab, Macrocheira kaempferi, was the second most abundant species, present in 14.0% of the observations and with 1002 individuals |
| the scavengers peaked at the carcass at night, and a predatory fish peaked by day | scavengers (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 |
| it kept a day-night rhythm | the occurrence of strong 24-h day-night driven behavioral rhythms of the most abundant species |
| The scavenging shows at a carcass. | scavengers (S. parasitica and M. kaempferi) and predators (P. gissu) alternated their occurrence |

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

https://doi.org/10.1016/j.biomaterials.2004.07.032

| The page says | The source says |
| :--- | :--- |
| scientists prepared molecularly aligned chitosan from its tendons and used it in a biomaterial for nerve regeneration | We 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 treatment (note: 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.) |