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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.
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.
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.
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]
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.
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.
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.
What to do if you are bitten
Sidewalk spiders are not dangerous to humans, but their bite is still unpleasant due to the following symptoms:
- redness, swelling, itching and burning of the bite site;
- headache;
- dizziness;
- weakness.
If you are bitten by a sidewalk spider, it is enough to apply ice to the wound and take antihistamines. The bite site can be treated with “Star” balm or Fenistil-gel.
We often mistake spiders for ordinary insects, but this is wrong. They have poisonous glands containing toxins at their disposal. All types of sidewalk spiders must be handled carefully to avoid the unpleasant sensations that bites from these little ones cause.
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%.
Recommendations
- ^ a b c d
Peter K. L. Ng;
Daniel Guino and Peter J. F. Davey (2008). "Systema Brachyurorum: Part I. An Annotated List of Extant Brachyuroran Crabs of the World" (PDF). Raffles Zoological Bulletin
.
17
: 1–286. Archived from the original (PDF) on 2011-06-06. - ^ 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
.
25
(5):1259–1279. Doi:10.1080/00222939100770781. ISSN 0022-2933. - ^ a b c d
"
Macrocheira kaempferi
".
Crabs of Japan
. Marine species identification portal. Retrieved March 29, 2010. - ^ a b c
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 - ^ a b
Riebel, William.
"Macrocheira kaempferi". Animal Diversity Network
. Retrieved 2020-03-09. - 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
.
3
: e715. doi:10.7717/peerj.715. ISSN 2167-8359. PMC 4304853. PMID 25649000. - Maurice Burton and Robert Burton (2002). "Spider Crab." International Wildlife Encyclopedia
(3rd ed.). Marshall Cavendish. pp. 2475–2476. ISBN 978-0-7614-7266-7. - ^ a b c
"Japanese spider crabs arrive at the aquarium."
Oregon Coast Aquarium
. Retrieved March 29, 2010. - 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) - Aquarium, Tennessee. "Giant Japanese Spider Crab - Tennessee Aquarium." www.tnaqua.org
. Retrieved April 6, 2022. - ^ a b c d
Wixten, Mary K. (1993).
"A review and model of decoration behavior of spider crabs (Decapoda, Brachyura, Majidae)". Crustaceans
.
64
(3):314–325. Doi:10.1163/156854093X00667. ISSN 0011-216X. JSTOR 20104855. - ^ a b c d
"Japanese spider crab". Georgia Aquarium. Archived from the original on October 4, 2013. Retrieved June 6, 2013. - ^ a b
"Japanese Spider Crab Care Guide" (PDF).
AZA Aquatic Invertebrate Taxa Advisory Group
. Silver Spring, MD: Association of Zoos and Aquariums. 2014. Archived from the original (PDF) on September 8, 2015. Retrieved February 23, 2016. - Okamoto, Kazutoshi (1995). "Pre-zoom stage of the giant spider crab Macrocheira kaempferi (Crustacea, Decapoda, Majidae)". Fisheries Science
.
61
(1): 161–162. doi:10.2331/fishsci.61.161. ISSN 0919-9268. - ^ a b c d f f
Kazutoshi Okamoto (1993).
"Effect of temperature on survival and growth of giant spider crab larvae." Macrocheira kaempferi
(Crustaceans, decapods, majids)" (PDF).
Nippon Suisan Gakkaishi
.
59
(3):419–424. doi:10.2331/suisan.59.419. Archived from the original (PDF) on 07/22/2011. - Riebel, W. (2011). "Macrocheira kaempferi". Animal Diversity Network. Retrieved June 3, 2022.
- ^ a b
"Japanese giant spider crab -
Macrocheira kaempferi
- Taka-ahi-gani." Natural art. Archived from the original on August 23, 2011. Retrieved March 29, 2010. - Hans G. Hansson. "Engelberg Kaempfer". Biographical etymology of the names of marine organisms
. Göteborgs Universitet. Retrieved March 29, 2010. - De Grave, Sammy; Pentcheff, N. Dean; Ahyong, Shane T.; and others. (2009). "Classification of living and fossil genera of decapod crustaceans" (PDF). Raffles Zoological Bulletin
. Suppl 21:1–109. Archived from the original (PDF) on 2011-06-06. - Macrocheira
at Fossils.org - ^ a b c d f g gram h
Sakai, K. (1987).
"Tun Sakai (1903-1986)". Crustaceans
.
53
(2):205–209. Doi:10.1163/156854087X00826. ISSN 0011-216X. JSTOR 20104298. - Kent E. Carpenter and Volker H. Niehm, eds. (1998). "Majidae" (PDF). Living marine resources of the western central Pacific Ocean.
Volume 2: Cephalopods, crustaceans, sea cucumbers and sharks . FAO Guide to Species Identification for Fisheries. Food and Agriculture Organization. pp. 1136–1137. ISBN 92-5-104052-4. - ^ a b c d f
"Giant Japanese spider crab." To the Tennessee Aquarium. Retrieved June 5, 2013.
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.
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.
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.
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:
- pain that occurs when punctured.
- Redness of the skin.
- 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.
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.
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.
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.
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.
