Overview

Distribution

Geographic Range

The Japanese spider crab Macrocheira kaempferi is mostly limited to the Pacific side of the Japanese islands, Konshu and Kyushu, usually at a latitude between 30 and 40 degrees North. They are found most often in the Sagami, Suruga, and Tosa bays, as well as off the coast of the Kii peninsula.  However, the crab has been found as far south as Su-ao, in Eastern Taiwan. This is most likely a one time event; it is possible a fishing trawler or extreme weather may have carried this individual much further south than its home range.

Biogeographic Regions: palearctic (Native )

  • Huang, J., H. Yu, M. Takeda. 1990. Occurence of the giant spider crab, Macrocheira kaempferi (Temmink, 1836) (Crustacea, Decapoda, Majidae) in Tawiwan. Bulletin of the Institute of Zoology, Academia Sinica, 29 (3): 207-212.
  • Okamoto, K. 1993. Influence of temperature on survival and growth of larvae of the giant spider crab Macrocheira kaempferi (Crustacea, Decapoda, Majidae). Bulletin of the Japanese Society of Scientific Fisheries, 59 (3): 419-424.
  • Okamoto, K. 2001. Limb loss in the giant spider crab Macrocheira kaempferi. Bulletin of the Shizuoka Prefectural Fisheries Experiment Station, 36: 25-27.
  • Park, E. 1988. Around the mall and beyond: Japenese spider crabs at the invertebrate exhibit at the national zoo. Smithsonian, 19: 18.
  • Sakai, K. 2010. "Macrocheira kaempferi" (On-line). Marine Species Identification Portal. Accessed May 02, 2011 at http://species-identification.org/species.php?species_group=crabs_of_japan&id=857&menuentry=soorten.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Physical Description

Morphology

Physical Description

Although not the heaviest, the Japanese giant spider crab is the largest known living arthropod. The well-calcified carapace is only around 37 centimeters long, but adult specimens can be nearly 4 meters long from one tip of one cheliped (a claw-bearing leg) to the other when stretched apart. The carapace of Macrocheira kaempferi is sub-circular and pear-shaped (pyriform), narrower towards the head. Females tend to have wider, although slightly smaller, abdomens than males. Spiny and stubby tubercles (growths) cover the carapace, which ranges from dark orange to light tan in color. It possesses no cryptic coloration and is unable to change color. The rostrum (an extension of the carapace above the head) is shaped into two slender spines that jut out from between the eyes. The base of the well-developed antennae is fused with the epistome (the area above the mouth).

The carapace tends to stay the same size throughout adulthood, but the walking legs and chelipeds lengthen considerably as the crab ages. Spider crabs are known for having long, spindly legs. Like the carapace, the legs are also orange, but may be blotchy and mottled with both orange and white. The walking legs of Macrocheira kaempferi end simply in inwardly-curving dactyls (the movable part at the tip of a walking leg). These assist the creature in climbing and hooking onto rock, but prevent it from picking up or grasping objects.  In adult males the chelipeds are far longer than any of the walking legs, with the right and left chelipeds being of equal size. Females, on the other hand, tend to possess chelipeds that are shorter than the other walking legs. The merus (upper portion of the leg) is slightly longer than the palm (portion of the leg containing the unmoving part of the claw), but comparable in shape. The weak movable finger is small, taking up less than a quarter of the palm.  Although long, the legs are often weak. One study reported that nearly three quarters of these crabs are missing at least one limb, most often one of the first walking legs. This is because the limbs are long and poorly-jointed to the body of the organism, and tend to come off due to predators and nets. Spider crabs can usually survive with up to 3 walking legs missing. The walking legs often grow back during the successive molts.

Range mass: 16 to 20 kg.

Range length: 3.7 (high) m.

Average length: 3 m.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: sexes shaped differently

  • Encyclopaedia Britannica Online, 2011. "Giant Crab" (On-line). Accessed May 02, 2011 at http://www.britannica.com/EBchecked/topic/232976/giant-crab?cameFromBol=true.
  • Sakai, T. 1965. The Crabs of Sagami Bay. Honolulu: East-West Center Press.
  • Wicksten, M. 1992. A review and a model of decorating behavior in spider crabs (Decapoda, Brachyura, Majidae). Crustaceana, 64 (3): 314-325.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Ecology

Habitat

Japanese spider crabs most often inhabit the sandy and rocky bottom of the continental shelf and slope at an average depth of 150-300 meters. They have, however been found at depths of 600 feet. During spawning season the crabs spend most of their time in shallower waters around 50 meters. In Suruga Bay, at depths of 300 meters, the temperature is around 10 degrees Celsius. Younger crabs tend to live in shallower areas with warmer temperatures.

Range depth: 50 to 600 m.

Average depth: 200 m.

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: benthic ; coastal

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Trophic Strategy

Food Habits

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. They occasionally eat living kelp and algae. Although they move slowly, giant crabs occasionally hunt for small marine invertebrates that they can catch easily. Mariners used to tell tales of M. kaempferi dragging sailors underwater and feasting on their flesh. This is generally regarded as untrue, although it is certainly plausible that one of these crabs would feast upon the dead body of a sailor who had previously drowned.

Animal Foods: fish; carrion ; aquatic crustaceans; other marine invertebrates

Plant Foods: algae; macroalgae

Other Foods: detritus

Primary Diet: omnivore ; detritivore

  • Ueda, R., T. Yasuhara, H. Sugita, Y. Deguchi. 1989. Gut microflora of the Japanese giant crab Macrocheira kaempferi. Bulletin of the Japanese Society of Scientific Fisheries, 55: 181.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Associations

Ecosystem Roles

Macrocheira kaempferi is not an active predator, as it mainly scavenges the seafloor for dead and decaying matter.

While nearly all spider crabs tend to decorate their carapaces with sponges and other items, M. kaempferi does it less than others because it has so few predators and therefore no need for camouflage. Sponges provide camouflage and protection for the crab; the spider crab carries the sponge to new areas and possibly provides it with drifting food.

Mutualist Species:

  • Sponges

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Predation

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. Although slow-moving, they use their claws against smaller predators.

Anti-predator Adaptations: cryptic

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Life History and Behavior

Behavior

Communication and Perception

Not much is known about communication in Macrocheira kaempferi. They often scavenge for food alone, and there is little communication between members of the species, even when isolated with other spider crabs in aquaria. The antennae are greatly reduced. The eyestalks are also short and stubby. Because these crabs are not active hunters and do not have many predators, their sensory systems are not as acute as those of many other decapods in the same area.

Communication Channels: visual

Perception Channels: visual ; tactile

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Life Cycle

Development

This species goes through two zoeal stages and one megalopa stage. The zoeal stages generally last between 12-37 days, a shorter duration than other crabs in the same region. The megalopa stage typically lasts an average of 30 days. During the first molt (the prezoeal stage) the hatchlings writhe about, eventually slowly drifting to the sea bed. Here, each hatchling thrashes about until it flicks up the spines on its carapace. This dislodges the cuticle, and allows it to wriggle out by twisting and pulling until it frees itself.

The optimal rearing temperature for all larval stages is between 15-18 degrees Celsius, while the survival temperature is 11-20 degrees Celsius. Larval stages can most likely be found at shallower depths, then later move to deeper waters. In Suruga Bay, the temperature at 300 meters is around 10 degrees, and only adults may be found at these depths. These survival temperatures are much higher than those of other decapod species in the region. In the lab, at optimum growth conditions, only around 75% survive the first zoeal stage. This number drops to around 33% for the second zoeal and megalopa stages.

Development - Life Cycle: metamorphosis

  • Clark, P., W. Webber. 1991. A redescription of Macrocheira kaempferi (Temminck, 1836) zoeas with a discussion of the classification of the Majoidea Samouelle, 1819 (Crustacea: Brachyura). Journal of Natural History, 25 (5): 1259-1279.
  • Okamoto, K. 1991. On the development, hatch and culture of eggs of giant spider crab, Macrocheira kaempferi. Bulletin of the Shizuoka Prefectural Fisheries Experiment Station, 26: 21-33.
  • Okamoto, K. 2003. Studies on the larval rearing of the giant spider crab, Macrocheira kaempferi-VII The effect of antibiotics on survival and growth of larvae. Bulletin of the Shizuoka Prefectural Fisheries Experiment Station, 38: 37-41.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Life Expectancy

Lifespan/Longevity

Relatively little is known information regarding the longevity of this species. It is often reported that one of these crabs may live to be 100 years old in its natural habitat, but this may be conjecture. Other reports indicate that M. kaempferi generally live for over half of a century.

Typical lifespan

Status: wild:
100 (high) years.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Reproduction

These spider crabs mate seasonally during early spring, from January through March. Mating behavior is rarely observed. Male crabs hold sperm in spermatophores, which are inserted into the female's abdomen using the first two chelipeds.

Even though juvenile stages are well-documented in laboratories, reproduction information concerning M. kaempferi in its natural habitat is sparse. Fertilization is internal. A female often lays up to 1.5 million eggs per season, but only a few survive. Eggs are around 0.63-0.85 mm in diameter. The hatching duration is around 10 days. The breeding duration is around one year, although exact times are not available.

Breeding interval: Giant Japanese spider crabs mate once a year, seasonally between January and April

Breeding season: Early spring

Range number of offspring: 1,500,000 eggs (high) .

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous

Females carry eggs on their backs and lower bodies during incubation until they hatch. In this way, the mother can stir the water with her back legs to oxygenate the eggs. After the eggs hatch, there is no parental investment and the larvae are left to fend for themselves.

Parental Investment: female parental care ; pre-hatching/birth (Protecting: Female)

  • Arakawa, K. 1964. On mating behavior of the giant Japanese crab, Macrocheira kaempferi. Researches on Crustacea, 1: 41-46.
  • Hartnoll, R. 1969. Mating in the Brachyura. Crustaceana, 16 (2): 161-181.
  • Okamoto, K. 1993. Influence of temperature on survival and growth of larvae of the giant spider crab Macrocheira kaempferi (Crustacea, Decapoda, Majidae). Bulletin of the Japanese Society of Scientific Fisheries, 59 (3): 419-424.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Conservation

Conservation Status

There is insufficient data concerning the conservation status for the Japanese spider crab. The catch of this species has declined considerably in the last 40 years. Some researchers have put forth a method for recovery which involves restocking with juvenile crabs artificially cultured in fisheries. In Japan, laws prohibit fishermen from catching M. kaempferi during mating season in the early spring, from January until April, in order to keep natural populations up and to give the species a chance to spawn.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

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.

Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Economic Importance for Humans: Positive

Macrocheira kaempferi is quite useful and important to the Japanese culture. The crabs are often served as a delicacy during the appropriate crab-fishing seasons and are eaten both raw and cooked. Because the walking legs are so long, researchers often use tendons from the legs or chelipeds. In some parts of Japan, it is popular to take and decorate the carapace. Macrocheira kaempferi is also common in aquaria because of its gentle disposition.

Positive Impacts: food ; body parts are source of valuable material; research and education

  • Freeman, S. 2010. ""Crabzilla": The biggest crab ever seen in Britain...and it's still growing" (On-line). Mail Online. Accessed May 02, 2011 at http://www.dailymail.co.uk/news/article-1250168/Biggest-crab-seen-Britain.html.
  • Yamaguchi, I., S. Itoh, M. Suzuki, M. Sakane, A. Osaka, J. Tanaka. 2003. The chitosan prepared from crab tendon I: the characterization and the mechanical properties. Biomaterials, 24 (12): 2031-2036.
Creative Commons Attribution Non Commercial Share Alike 3.0 (CC BY-NC-SA 3.0)

© The Regents of the University of Michigan and its licensors

Source: Animal Diversity Web

Trusted

Article rating from 0 people

Average rating: 2.5 of 5

Wikipedia

Japanese spider crab

The Japanese spider crab (高脚蟹 takāshigani?, lit. "tall-footed crab"), Macrocheira kaempferi, is a species of marine crab that lives in the waters around Japan. It has the largest leg span of any arthropod, reaching up to 3.8 metres (12 ft) and weighing up to 19 kilograms (42 lb). It is the subject of small-scale fishery which has led to a few conservation measures.

Description[edit]

A Japanese spider crab at the Manila Ocean Park

The Japanese spider crab has the greatest leg span of any arthropod, reaching 3.8 metres (12 ft) from claw to claw. The body may grow to a size of 40 cm or 16 in (carapace width) and the whole crab can weigh up to 19 kilograms (42 lb).[2] The males have the longer chelipeds;[3] females have much shorter chelipeds, which are shorter than the following pair of legs.[4] Apart from its outstanding size, the Japanese spider crab differs from other crabs in a number of ways. The first pleopods of males are unusually twisted, and its larvae appear primitive.[1] The crab is orange, with white spots along the legs.[5] It is reported to have a gentle disposition "in spite of its ferocious appearance".[5]

Distribution[edit]

Giant Japanese Spider Crab, Shedd Aquarium, Chicago

Japanese spider crabs are mostly found off the southern coasts of the Japanese island of Honshū, from Tokyo Bay to Kagoshima Prefecture. Outlying populations have been found in Iwate Prefecture and off Su-ao in Taiwan.[4] Adults can be found at depths of up to 600 m (2,000 ft), or as shallow as 50 m (160 ft).[4] They like to inhabit vents and holes in the deeper parts of the ocean.[6]

Life cycle[edit]

A large male specimen

Female crabs carry the fertilized eggs attached to her abdominal appendages until they hatch into tiny planktonic larvae.[6] Development of the planktonic larvae is temperature-dependent and takes between 54 and 72 days at 12–15 °C (54–59 °F).[7] During the larval stage the young crab looks nothing like its parents. It is small and transparent with a round, legless body and usually drifts as plankton at the surface of the ocean.[6] The Japanese spider crab is an omnivore, consuming both plant matter and animals. It also sometimes acts as a scavenger consuming dead animals. Some have been known to scrape the ocean floor for plants and algae while others pry open the shells of mollusks.[5][6] They live at depths of 150 metres (490 ft)-300 metres (980 ft) or more.[8] The giant spider crabs migrate up to a depth of around 50 metres (160 ft) during breeding season.[8]

Taxonomic history[edit]

The Japanese spider crab was originally described in 1836 by Coenraad Jacob Temminck under the name Maja kaempferi, based on material from Philipp Franz von Siebold collected near the artificial island Dejima.[9] The specific epithet commemorates Engelbert Kaempfer, a German naturalist who lived in Japan from 1690 to 1692 and wrote about the country's natural history.[10] It was moved to the genus Inachus by Wilhem de Haan in 1839, but placed in a new subgenus, Macrocheira. That subgenus was raised to the rank of genus in 1886 by Edward J. Miers.[1] Although currently placed in the family Inachidae, M. kaempferi does not fit cleanly into that group, and it may be necessary to erect a new family just for the genus Macrocheira.[1] As well as the single extant species, four species belonging to the genus Macrocheira are known from fossils.[11]

Fishery[edit]

Temminck, in his original description, noted that the crab was known to the Japanese for the serious injuries it can cause with its strong claws.[3] The Japanese spider crab is "occasionally collected for food,"[12] and even considered a delicacy in many parts of Japan and other areas in the region.[6][8] A total of 24.7 tonnes (54,000 lb) were collected in 1976, but only 3.2 tonnes (7,100 lb) in 1985.[7] The fishery is centred around Suruga Bay and they are caught using small trawling nets.[8] The population has decreased in number, forcing fishermen into exploring deeper waters to catch them. Harvesting of the crab is forbidden during the spring, when crabs move to shallower water to reproduce.[8] Populations of this species of crab have diminished over recent years and there are many efforts to protect them. The average size caught by fishermen is a leg span of 1.0–1.2 m (3 ft 3 in–3 ft 11 in).[9]

See also[edit]

References[edit]

  1. ^ a b c d Peter K. L. Ng, Danièle Guinot & Peter J. F. Davie (2008). "Systema Brachyurorum: Part I. An annotated checklist of extant Brachyuran crabs of the world" (PDF). Raffles Bulletin of Zoology 17: 1–286. 
  2. ^ Maurice Burton & Robert Burton (2002). "Spider crab". International Wildlife Encyclopedia (3rd ed.). Marshall Cavendish. pp. 2475–2476. ISBN 978-0-7614-7266-7. 
  3. ^ a b G. F. Mees (1957). "Over het belang van Temminck's "Discours Préliminaire" voor de zoologische nomenclatuur" [On the importance of Temminck's "Discours Préliminaire" for zoological nomenclature]. Zoologische Mededelingen (in Dutch) 35 (15): 205–227. "on dit, que ce Crustacé est redouté des habitants par les blessures graves, qu'il est en état de faire au moyen de ses fortes serres" 
  4. ^ a b c "Macrocheira kaempferi". Crabs of Japan. Marine Species Identification Portal. Retrieved March 29, 2010. 
  5. ^ a b c "Japanese Spider Crabs Arrive at Aquarium". Oregon Coast Aquarium. Retrieved March 29, 2010. 
  6. ^ a b c d e "Japanese Spider Crab". Georgia Aquarium. Retrieved 6 June 2013. 
  7. ^ a b Kazutoshi Okamoto (1993). "Influence of temperature on survival and growth of larvae of the giant spider crab Macrocheira kaempferi (Crustacea, Decapoda, Majidae)" (PDF). Nippon Suisan Gakkaishi 59 (3): 419–424. 
  8. ^ a b c d e "Giant Japanese Spider Crab". The Tennessee Aquarium. The Tennessee Aquarium. Retrieved 5 June 2013. 
  9. ^ a b "The Japanese Giant Spider Crab - Macrocheira kaempferi - Taka-ahi-gani". Natural Art. Retrieved March 29, 2010. 
  10. ^ Hans G. Hansson. "Engelberg Kaempfer". Biographical Etymology of Marine Organism Names. Göteborgs Universitet. Retrieved March 29, 2010. 
  11. ^ Sammy De Grave, N. Dean Pentcheff, Shane T. Ahyong et al. (2009). "A classification of living and fossil genera of decapod crustaceans" (PDF). Raffles Bulletin of Zoology. Suppl. 21: 1–109. 
  12. ^ Kent E. Carpenter & Volker H. Niem, ed. (1998). "Majidae" (PDF). The Living Marine Resources of the Western Central Pacific. Volume 2: Cephalopods, crustaceans, holothurians and sharks. FAO Species Identification Guide for Fishery Purposes. Food and Agriculture Organization. pp. 1136–1137. ISBN 92-5-104052-4. 
Creative Commons Attribution Share Alike 3.0 (CC BY-SA 3.0)

Source: Wikipedia

Unreviewed

Article rating from 0 people

Average rating: 2.5 of 5

Disclaimer

EOL content is automatically assembled from many different content providers. As a result, from time to time you may find pages on EOL that are confusing.

To request an improvement, please leave a comment on the page. Thank you!