Giant Japanese spider crab: what is known about the huge arthropod

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The giant spider crab is the largest known species and can live up to 100 years. The Japanese name for the species is taka-ashi-gani, which literally means “high-legged crab.” Its bumpy shell blends into the rocky ocean floor. To enhance the illusion, the spider crab decorates its shell with sponges and other animals. Although these creatures scare many with their spider-like appearance, they are still an amazing and fascinating wonder hidden in the deep ocean.

Origin of the species and description

Photo: Spider Crab

The Japanese spider crab (タカアシガニ or "long-legged crab"), or Macrocheira kaempferi, is a species of sea crab native to the waters around Japan. It has the longest legs of any arthropod. It is a fishery item and considered a delicacy. Two fossil species have been discovered belonging to the same genus, ginzanensis and yabei, both found during the Miocene period in Japan.

Video: Spider Crab

There was much controversy during the classification of the species based on larvae and adults. Some scientists support the theory of a separate family for this species and believe that further research is needed. Today the species is the only known surviving member of the Macrocheira, and is considered one of the earliest branching members of the Majidae. For this reason, it is often called a living fossil.

In addition to one extant species, a number of fossils are known to have once belonged to the genus Macrocheira:

• Macrocheira sp. — Pliocene Takanabe Formation, Japan;
• M. ginzanensis - Miocene form of ginzan, Japan;
• M. Yabei - Miocene Yonekawa Formation, Japan;
• M. teglandi - Oligocene, east of Twin River, Washington, USA.

The spider crab was first described in 1836 by Coenraad Jacob Temminck under the name Maja kaempferi, based on material collected near the artificial island of Dejima by Philipp von Siebold. The specific epithet was given in memory of Engelbert Kaempfer, a naturalist from Germany who lived in Japan from 1690 to 1692. In 1839 the species was placed in a new subgenus, Macrocheira.

This subgenus was elevated to genus in 1886 by Edward J. Myers. The spider crab (M. kaempferi) has been placed in the family Inachidae, but does not fit neatly into this group, and it may be necessary to create a new family exclusively for the genus Macrocheira.

Nutrition

Despite their body size, these arthropods are predators. They do not weave spider webs to catch prey. They only need the web for comfortable movement.

Small predators blend into their environment, waiting for their prey. They can remain absolutely motionless for a long time. They attack not only small insects - they also prey on those whose size is larger than the hunter.

During an ambush, cunning predators camouflage themselves, spread their forelimbs wide, preparing to attack instantly. If there is prey nearby, the arthropod approaches the victim and injects poison.

Toxic substances affect the victim’s nervous system, immobilizing it for a long time. This aggressive behavior is explained by the fact that the spider's front legs are equipped with claws, which contain a powerful poison that paralyzes prey.

When the victim is immobilized, the arthropod sucks all the vital juices out of it. Due to its weak jaw and small size, the sidewalker does not absorb its food entirely. Bumblebees, locusts, bees, and flies serve as food.

Appearance and features

Photo: Animal crab spider

The Japanese giant spider crab, although not the heaviest in the underwater world, is the largest known arthropod. A well-calcified carapace is only about 40 cm, but the total length of adults can be almost 5 meters from one tip of the cheliped (claw with claws) to the other when stretched. The shell has a round shape, and closer to the head it is pear-shaped. The entire crab weighs up to 19 kg - second only to the American lobster among all living arthropods.

Females have a wider but smaller belly than males. Spiny and short tubercles (growths) cover the carapace, which varies from dark orange to light brown. It does not have a mysterious coloration and cannot change color. The continuation of the shell on the head has two thin spikes protruding between the eyes.

The shell tends to remain the same size throughout adult life, but the claws lengthen significantly as the crab ages. Spider crabs are known for having long, thin limbs. Like the shell, they are also orange, but can be spotted, with spots of both orange and white. Walking claws end in inwardly curved movable parts at the tip of the walking limb. They help the creature climb and cling to rocks, but do not allow the creature to lift or grab objects.

In adult males, the chelipeds are much longer than any of the walking legs, with the right and left claw-bearing chelipeds being the same size. On the other hand, females have chelipeds that are shorter than other walking limbs. The merus (upper leg) is slightly longer than the palm (the part of the leg that contains the fixed part of the claw), but is comparable in shape.

Although the legs are long, they 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 connected to the body and tend to be torn off by predators and nets. Crab spiders can survive without up to 3 walking legs. Walking legs can grow back during the next molt.

Nephila the goldweaver

A spider that belongs to the species that weaves the largest webs in the world. On average, the size of female and male individuals does not exceed thirteen centimeters. The color is yellow-greenish, and the belly and head are white.

Nephila the goldweaver

They are poisonous, but their poison cannot kill a person. They live in arid countries. They live no more than a year, and die within a couple of days after mating. Only females weave webs. The threads have a golden glow, which is why these spiders are called golden weavers. Webs are very strong, people decided to take advantage of this. In America, in the Museum of Natural History, there is a canvas created from nephil webs.

Where does the spider crab live?

Photo: Japanese spider crab

The habitat of the Japanese arthropod giant is limited to the Pacific side of the Japanese Honshu Islands from Tokyo Bay to Kagoshima Prefecture, usually at a latitude of 30 to 40 degrees north. They are most often found in Sagami, Suruga and Tosa bays, as well as off the coast of the Kii Peninsula.

The crab has been found as far south as Su-ao, in eastern Taiwan. This is most likely a random event. It is possible that a fishing trawler or extreme weather helped move these individuals much further south than their home range.

Japanese spider crabs most often live on the sandy and rocky bottom of the continental shelf at depths of up to 300 meters. They like to hide in vents and holes in the deep parts of the ocean. Temperature preferences are unknown, but spider crabs are regularly found at depths of 300 m in Suruga Bay, where water temperatures are around 10°C.

It is almost impossible to meet a spider crab because it wanders in the depths of the ocean. Based on research in public aquariums, spider crabs can tolerate temperatures of at least 6–16°C, but are comfortable at 10–13°C. Juveniles tend to live in shallower areas with warmer temperatures.

Goliath tarantula

The spider is of impressive size, can reach 170 grams, its height including legs is 30 cm, belongs to the tarantula family. Lives in the tropics of South America. It builds burrows up to half a meter deep with the entrance covered with cobwebs. Females can survive up to 25 years, males - up to 6.

Goliath suddenly sneaks up and quickly pounces on its prey, poisoning it with its poisonous fangs. It feeds on frogs, small snakes, mice and birds.

The Goliath tarantula is capable of producing powerful sounds with its chelicerae, which can be heard even 5 meters away. To defend themselves, they use their bright brown hairs, which irritate the mucous membranes of the mouth and nose, which the spider shakes off its body towards the enemy.

What does a spider crab eat?

Photo: Large spider crab

Macrocheira kaempferi is an omnivorous scavenger, consuming both plant matter and animal parts. It is not an active predator. Basically, these large crustaceans tend not to hunt, but rather crawl and collect dead and decaying matter along the seabed. By their nature they are detritivores.

The spider crab's diet includes:

• small fish;
• carrion;
• aquatic crustaceans;
• marine invertebrates;
• seaweed;
• macroalgae;
• detritus.

Sometimes they eat algae and live shellfish. Although giant spider crabs move slowly, they are able to hunt small marine invertebrates that they can easily catch. Some individuals clean the ocean floor of decaying plants and algae, and some open mollusk shells.

In earlier times, sailors told frightening stories of how a terrible spider crab would drag a sailor underwater and feast on his flesh in the depths of the ocean. This is considered untrue, although it is likely that one of these crabs could feast on the dead body of a sailor who had drowned earlier. The crustacean has a gentle character, despite its fierce appearance.

The crab has been known to the Japanese for a long time because of the damage it can do with its strong claws. It is often caught for food and is considered a delicacy in many regions of Japan and other parts of the world.

Behavior

In the ocean, arthropods become easy prey for squids and octopuses. The constant proximity of predators forces the crab to come up with new ways to survive. For this he is called a smart creature. He behaves very carefully, pays attention to little things that signal the appearance of an enemy. Deep-sea “spiders” are able to hide perfectly in any conditions. Some individuals grow tubercles containing poison on their shells, which paralyze aggressors.

In aquariums, oceanariums, natural museums and nature reserves, where animals are cared for and food is supplied, arthropods are friendly and do not cause harm. This confirms the crab’s ability to learn and indicates that the animal adequately perceives the world around it and is able to adequately assess risks.

Features of character and lifestyle

Photo: Sea spider crab

Spider crabs are very quiet creatures that spend most of their days searching for food. They wander along the seabed, moving easily over rocks and potholes. But this sea animal cannot swim at all. Crab spiders use their claws to tear apart objects and attach them to their shell. The older they get, the larger their size. These spider crabs shed their shells, and new ones grow even larger as they age.

One of the largest spider crabs ever caught was only forty years old, so there's no telling what size they might be when they reach 100 years old!

Little is known about how spider crabs communicate with each other. They often forage alone and there is little contact between members of this species, even when isolated and kept in aquariums. 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 from the same region. In Suruga Bay, at a depth of 300 meters, where the temperature is about 10°C, only adult individuals can be found.

The Japanese variety of crabs belongs to the group of so-called “decorator crabs”. These crabs are so named because they collect various objects in their environment and cover their shells with them as camouflage or protection.

1.Goliath tarantula

It is rightly called the largest spider in the world. With outstretched legs the size of a Goliath, in the mouth there are fangs with poison, 2.5 cm in size. This species of tarantula spider lives in South America. The color is all shades of brown, with characteristic transverse white stripes on the paws. He likes to be in damp, swampy places; here he digs holes half a meter deep and covers them with cobwebs. Contrary to their name, they rarely feed on birds; their diet consists of snakes, rodents, toads, lizards, and butterflies. At night, the spider sees well, it waits for prey in ambush, then pounces on it with great speed and bites with large fangs. It is aggressive, before attacking it makes strong sounds and shakes off an irritating allergenic substance from its hairs. Goliath's venom is quite weak, but the biggest danger is the hairs, which can cause allergies or asthma.

Social structure and reproduction

Photo: Red spider crab

At 10 years old, the spider crab becomes sexually mature. Japanese laws prohibit fishermen from catching M. kaempferi during the early spring mating season, January to April, to preserve natural populations and allow the species to spawn. Giant spider crabs mate once a year, seasonally. During spawning, crabs spend most of their time in shallow water about 50 meters deep. The female lays 1.5 million eggs.

During incubation, females carry the eggs on their back and lower body until they hatch. The mother stirs the water with her hind legs to oxygenate the eggs. After the eggs hatch, parental instincts are absent, and the larvae are left to fend for themselves.

Female crabs carry fertilized eggs attached to their abdominal appendages until tiny planktonic larvae hatch. The development of planktonic larvae is temperature dependent and takes 54 to 72 days at 12–15 °C. During the larval stage, young crabs do not resemble their parents. They are small and transparent, with a round, legless body that drifts as plankton on the surface of the ocean.

This species goes through several stages of development. During their first moult, the larvae slowly drift toward the seabed. There the cubs rush in different directions until they click on the spikes on their shell. This allows the cuticles to move until they are released.

The optimal rearing temperature for all larval stages is 15-18°C, and the survival temperature is 11-20°C. The first stages of larvae can be observed in shallower depths, and then the growing individuals move to deeper waters. The survival temperature of this species is much higher than that of other decapod species in the region.

In the laboratory, under optimal growth conditions, only about 75% survive the first stage. At all subsequent stages of development, the number of surviving cubs decreases to approximately 33%.

Nephila edulis

Nephila goldweaver occupies the last place in the ranking among large spiders. This creature can be found in Africa, Asia, South America and Australia. Their home is trees; on the branches they hang strong golden nets up to one and a half meters in diameter. This deadly web is capable of trapping not only insects, but also small birds. The female nephila golden moth has a body of about 4 cm, and its overall size is 13 cm, which is approximately 1.5 times larger than males. The color of the spider is mainly yellow-green with reddish splashes. Its poison is toxic to humans, but does not pose a serious threat.

Natural enemies of the spider crab

Photo: Giant Japanese spider crab

The adult spider crab is quite large in size, so it has few predators. It lives deep, which also affects safety. Young individuals try to decorate their shells with sponges, algae or other objects suitable for camouflage. However, adults rarely resort to this method because their large size deters most predators from attacking them.

Although spider crabs move slowly, they use their claws against small predators. The armored exoskeleton helps the animal protect itself from larger predators. But even though these spider crabs are massive, they still have to watch out for the occasional predator, such as an octopus. So they really need to camouflage their huge bodies well. They do this using sponges, brown algae and other substances. Their carapace is mottled and uneven, much like a rock or part of the ocean floor.

Japanese fishermen continue to catch spider crabs even though their numbers are declining. Scientists fear its population may have declined significantly over the past 40 years. Often in animals, the larger it is, the longer it lives. Just look at the elephant, which can live for more than 70 years, and the mouse, which lives on average up to 2 years. And since the spider crab reaches sexual maturity late, there is a chance that it will be caught before it reaches it.

Population

Over the past half century, the number of spider crabs has greatly decreased. This is caused by overharvesting of animals. In Japanese cuisine, the animal is highly valued as a healthy and tasty delicacy. They like to be placed in aquariums in restaurants. Scientists are fighting to preserve the population of the species and use the method of artificially rearing young individuals in various fish farms in Japan.

For cooking, only young crabs that have not given birth are used. Their meat has a delicate taste and is very soft. They are used as exotic interiors.

Anatomy

Macrocheira kaempferi

it is a giant crab with a pear-shaped shell that measures 350 mm when measured along the midline.[21] Its surface is covered with small protrusions or tubercles. The spine of an adult giant crab is short and curves outward at the end. On the other hand, the spines of young giant crabs are long compared to their shell, along with an uncurved spine.[21] This proportionality explains, as in other decapod crustaceans, that the size of spines decreases as individuals mature.[21] As mentioned in the taxonomic section, this genus contains the primitive feature of a family of motile antennae in the basal segment. However, "the development of a spine at the posterior angle of the supraorbital eaves and the presence of an intercalated spine and antennular septum seem to assign this genus a rather high position." Finally, there are differences between the sexes. Adult males have very long front legs where the claws are located, but they are still shorter than the walking legs of females, located at the back of the shell and used for locomotion.[21]

What's special about it

The Huntsman spider family is very numerous: it includes 1090 species. They can most often be found in the tropics; there are isolated species in the Palearctic.

Giant crab spider - Olios giganteus

The giant crab spider is the largest member of the family. He is an inhabitant of Australia, which has many unique species of insects, animals and reptiles. There are 155 species of huntsman spiders recorded on the continent, but this one is the largest of them all.

Appearance

This arthropod cannot be confused with anyone else: the length of the limbs reaches 30 cm. True, only females can boast of such a size.

Giant crab spider

Males are 2 times smaller, but 15 cm is also a lot for a spider. In size and weight it is second only to the goliath tarantula, ranking 2nd in the world according to these indicators.

Goliath tarantula

Some researchers believe that the giant crab spider is the largest.

It also has other features that allow you to accurately identify the insect:

• unusually curved long hairy limbs, for which it received the name crab, allow it to move not only forward, but also sideways;
• the pubescent body up to 4.6 cm long may have a grayish, light brown or black color;
• 8 eyes located on the sides of the cephalothorax in 2 rows provide excellent all-round visibility;
• The giant crab spider is no different in visual acuity - it sees only moving silhouettes and shadows;
• powerful jaws allow you to cope with even small rodents.

In order to turn its legs 180 degrees and plunge its jaws into its prey, the spider only needs 1/8 of a second - amazing speed! A photo of a crab spider will allow you to estimate the size of the insect and examine it in all details.

How does a giant spider live and hunt?

The crab spider prefers to live in trees, crevices in stones, and sometimes hides under fallen leaves or behind loose tree bark.

In rainy weather, this giant can “visit” a person’s home - the special structure of its legs allows it to crawl through even a narrow crack.

Giant crab spider on the wall of a house

He feels at ease there. The owner is not particularly shy, hides behind the curtains or crawls along the walls, happily destroying domestic pests: there is a tangible benefit from the uninvited guest.

Unlike many other arachnids, the hunter does not catch his victims using a web, so he does not weave one.

However, the arthropod has a gland for spinning thread: with its help, the spider holds on to plant stems or tree branches while searching for food.

He prefers to hunt from ambush, patiently waiting for his prey:

1. insects, including smaller relatives;
2. lizards;
3. frogs;
4. rodents, however, he rarely catches them.

The prey is instantly paralyzed by the injected poison, and then fermented by the injected saliva, which makes it easier to digest.

Crab spider mouthparts

The Australian hunting spider moves very quickly, covering a whole meter in 1 second. He can not only run, but also jump high, overtaking the victim.

This representative of arachnids prefers a nocturnal lifestyle. Most often it lives alone, but sometimes you can observe a whole colony of insects gathered together and occupying a fallen tree or stump.

Reproduction

Mating is preceded by a period of courtship. After fertilization, the female is rarely aggressive, so most males are not in danger, unlike many other spider species. In order for the laid eggs to successfully turn into small spiderlings, they need a cocoon of cobwebs, which the female weaves.

Spider guarding its cocoon

She can lay up to 200 eggs in it. The female Huntsman spider is a caring mother: during the three weeks while the eggs are developing, she does not leave the cocoon and bravely protects it from enemies.

The spiderlings that have just emerged from the eggs are not yet fully developed and are absolutely helpless. At the nymph stage, they molt several times until a hard chitinous exoskeleton is formed, which spiders will shed repeatedly throughout their lives, acquiring a new one. After a few weeks, the young individuals become independent.

Habitats

Scientists suggest that this amazing long-legged creature can live up to a hundred years. Some doubt it, putting a more modest figure - a little over 50 years.

This Japanese crab lives at a depth of 200-300 meters, sometimes at a depth of 150-200 meters. In the spring, during the egg-laying period, it rises to the surface and is found at 50 meters. Most often these giants are found in the area of ​​​​the Japanese islands - Kyushu and Honshu. It is rare, but still possible, to encounter these creatures in the Russian Far East.

This amazing creature was first described by Japanese researchers in the 17th century. And information about the unusual Japanese crab came to the West only at the end of the 20s of the 18th century thanks to the works of the German Engelbert Kampfer, a famous biologist of those times. Later, the giant will be named after its European discoverer; in scientific literature you can find the Latin name Macrocheira kaempferi. Then the crustacean was described by the Dutch zoologist Konrad Jacob Temminck.

Interesting facts about sidewalkers

• Some species have the ability to slowly change their color.
• Before mating, the male brings his lady a gift in the form of an edible insect.
• Some people specifically bring home cockroaches to get rid of cockroaches.
• Spiders are able to distinguish the sounds of music and even “dance.”
• They distinguish relatives at a distance of up to 5 meters.
• Because of their style of moving sideways, they are called crab spiders.
• Some species hunt exclusively at night, waiting for moths inside a flower.
• They do not attack insects that are much smaller in size than the spider’s body.
• Farmers move sidewalkers to their fields to get rid of pests.
• Due to the small size of the fangs, they are not able to bite through human skin.

Recommendations

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   : 1–286. Archived from the original (PDF) on 2011-06-06.
2. ^ a b c
   Clark, Paul F.;
   Webber, W. Richard (October 1991). "Redescription of Macrocheira kaempferi (Temminck, 1836) zoeas with discussion of the classification of Majoidea Samouelle, 1819 (Crustacea: Brachyura)". Journal of Natural History
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   Macrocheira kaempferi
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   G. F. Mies (1957).
   "Over het belang van Temminck's" Discours Préliminaire "voor de zoologische nomenclatuur" [On the importance of Temminck's "Preliminary Discourses" for zoological nomenclature]. Zoologische Mededelingen
   (in Dutch).
   35
   (15): 205–227. on dit, que ce Crustacé est redouté des Hournts par les, qu'il est en état de faire au moyen de ses fortes serres
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   Riebel, William.
   "Macrocheira kaempferi". Animal Diversity Network
   . Retrieved 2020-03-09.
6. McClain, Craig R.; Balk, Megan A.; Benfield, Mark S.; Branch, Trevor A.; Chen, Catherine; Cosgrove, James; Dove, Alistair D.M.; Gaskins, Lindsey S.; Helm, Rebecca R. (January 13, 2015). "Sizing ocean giants: patterns of intraspecific size variation in marine megafauna." PeerJ
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   Oregon Coast Aquarium
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9. Okamoto, Kazutoshi (01/05/2009). "Moulting of the giant spider crab Macrocheira kaempferi in captivity" (PDF). Bulletin of the Shizuoka Prefectural Fisheries Research Institute
   . Vol. 43: 67–70 - via Aquatic Sciences and Fisheries Abstracts (ASFA) 1: Biological Sciences and Living Resources. Check date values ​​in: | date = (help)
10. Aquarium, Tennessee. "Giant Japanese Spider Crab - Tennessee Aquarium." www.tnaqua.org
    . Retrieved April 6, 2022.
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    Wixten, Mary K. (1993).
    "A review and model of decoration behavior of spider crabs (Decapoda, Brachyura, Majidae)". Crustaceans
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    Nippon Suisan Gakkaishi
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    Macrocheira kaempferi
    - Taka-ahi-gani." Natural art. Archived from the original on August 23, 2011. Retrieved March 29, 2010.
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Varieties

Sidewalk spiders are terrestrial animals. They are found everywhere on the globe. In warm climates, species diversity is much wider than in temperate and cold climates.

Spiders adapt to climatic conditions in various ways. One of them is coloring. All varieties of bocod spiders have their own shade. This family has 170 genera, in which about 2000 species are distinguished. The most studied types are:

Flower spider (Misutnena vatia)

• color white, yellowish;
• body size up to 11 mm;
• lives on flowers of the ranunculaceae and cornflower family;
• food: butterflies, bumblebees, bees;
• Habitat: Europe, North America.

Yellow crab spider (Xisticus luctuosus)

• the body of the male is dark brown, 4-5 mm long, the female is yellow – 7-8 mm;
• lives in meadows and forest clearings;
• distributed in the European part of Russia and the former USSR.

Ornamented blueberry (Synaema ornatum)

contrasting color: the bottom of the abdomen is black, the top is red or yellow with a black angular spot;

• body length of a male is 5-6 mm, female – 7-8 mm;
• lives on flowers of the Rosaceae family;
• feeds on insects;
• lives in the steppe and forest-steppe of our country.

The corn borer is a pest of corn, millet, barley and sunflower.

Danger to humans

Those who have had the chance to meet this giant arthropod first of all want to know what danger this meeting brings. The size of the insect causes hostility among people, even if the person does not suffer from arachnophobia.

Indeed, an encounter with such an arthropod can be quite unpleasant. Powerful jaws that crush reptiles will easily bite through skin.

Due to their large size, crab spiders bite very sensitively, but a collision with a predator does not pose a mortal danger.

Possible consequences of a bite for an adult:

1. pain that occurs when punctured.
2. Redness of the skin.
3. Edema, swelling.

All of these symptoms disappear after a few days and, as a rule, do not require medical intervention. In people prone to allergies, as well as young children, the consequences of a bite may be more pronounced.

Occasionally, typical signs of intoxication are observed: nausea, diarrhea, muscle pain, general weakness, difficulty breathing.

All symptoms go away within a couple of days. To alleviate the condition, you can take antihistamines. Difficulty breathing indicates a severe allergy to the predator's venom. This condition requires immediate medical intervention.