The largest representative of arthropods is the coconut crab or palm thief.
Seeing this amazing arthropod, anyone faint of heart will shudder with horror and surprise - after all, there is nothing in the world more interesting and, at the same time, more terrible than the coconut crab. In any case, among arthropods - after all, he is rightfully considered their largest representative.
The coconut crab has many other “names”: for example, thief crab or palm thief - after all, this strange arthropod actually steals its prey. Travelers of past centuries who visited the islands located in the Western Pacific Ocean and the Indian Ocean talk about how the coconut crab hides from prying eyes in the dense greenery of palm trees in order to then suddenly grab its prey lying right under a tree or nearby From him.
Strictly speaking, calling the palm thief a land arthropod is also a stretch, since part of its life is spent in the sea elements, and even tiny crustaceans are born in the water column. Newborn babies with a defenseless soft abdominal cavity busily crawl along the bottom of a reservoir in search of a reliable home, which can serve as a nut shell or an empty mollusk shell.
In truth, most legends noted precisely this feature - the first Europeans who arrived on the islands described coconut crabs as creatures hiding in the foliage of trees with long claws that suddenly reached out to the ground and captured prey, including sheep and goats. Scientists have confirmed that birgus latro has great strength and can lift up to 30 kg of weight. However, they found out that the crab uses its abilities to drag cargo from place to place, preferring to feed on dead animals, crabs and fallen fruits.
Those wishing to meet such a miracle would have to go to the tropics - coconut crabs are found on the islands of the Indian Ocean and on some Western Pacific islands. It is not easy to see them in daylight: palm thieves are nocturnal, and in sunny times they hide in rock crevices or in sandy burrows lined with coconut fibers - this helps maintain the required level of humidity in the home.
Coconut crab meat is not only considered a delicacy, but also an aphrodisiac, which is why these arthropods are actively hunted. To prevent their complete extinction, some countries have strict restrictions on the harvesting of coconut crabs.
As the name suggests, this crab feeds on coconuts, and is in fact able to climb up to a height of 6 meters on a coconut tree, where it uses its powerful claws to pinch off coconuts if they are not already available on the ground. If a fallen coconut does not split when it falls, the crab will gut it for a week or even two until it gets to the juicy pulp of the nut. If the crab gets tired of this dreary work, he lifts the coconut up the tree and throws it down to make his work easier. Descending back to the ground, they sometimes fall, but without damage to their health they can survive a fall from a height of 4.5 meters. The coconut crab will not refuse other fruits, newborn turtles and carrion. They have also been observed catching and eating Polynesian rats.
Its other name is palm thief, it received for its love of everything shiny. If a spoon, fork, or other shiny object gets in the way of a crab, you can be sure that he will certainly try to drag it into his hole.
From the beginning of June to the end of August, the breeding season begins for palm thieves. The courtship process lasts long and tediously, but mating itself occurs quite quickly. The female carries fertilized eggs for several months on the underside of her abdomen. When the eggs are ready to hatch, the female goes down to the seashore at high tide and releases the larvae into the water. Over the next three to four weeks, the larvae floating in the water go through several stages of development. After 25 - 30 days, small crabs sink to the bottom, settle in the shells of gastropods, and prepare to migrate to land. At this time, babies sometimes visit land, and gradually losing the ability to breathe under water, they finally move to the main habitat. Coconut crabs reach sexual maturity about five years after hatching, but do not reach their maximum size until they are 40 years old.
Palm thieves live in the tropics, on the islands of the Indian and western Pacific oceans. Christmas Island in the Indian Ocean has the highest population density of coconut crabs in the world.
Swedish and Australian scientists have confirmed the veracity of all the stories about coconut crabs. Thus, residents of the Pacific Islands claimed that they could smell, for example, meat or ripe fruit several kilometers away. And indeed, the special baits placed by the researchers immediately attracted the attention of the thieving crabs, who nevertheless disdained the ordinary pieces of bread that ordinary crabs are greedy for.
The function of a janitor is, of course, not bad and useful, however, since Birgus latro is a predominantly nocturnal creature and not very friendly, local residents are not particularly delighted when they stumble upon it. The decrease in its numbers forced local authorities to set a limit on catching birgus latro. In Papua New Guinea it is prohibited to include it in restaurant menus, on the island of Saipan it is prohibited to catch crabs with a shell less than 3.5 cm, and also from June to September, during the breeding season.
On the inner surface of the walls of the gill cavities, this land descendant of hermit crabs develops grape-shaped folds of skin in which numerous blood vessels branch. These are real lungs, allowing the use of oxygen from the air filling the gill cavities. The lungs are ventilated due to the movements of the scaphognathite, as well as due to the ability of animals from time to time to raise and lower the carapace, for which special muscles are used.
It is remarkable that the gills are also preserved, although they are relatively small in size. Removing the gills did not harm breathing at all; on the other hand, the crayfish completely lost the ability to breathe in water. The palm thief immersed in water died after 4 hours. The residual gills apparently do not function. The palm thief digs shallow burrows in the soil, which are lined with coconut fibers. Charles Darwin says that the natives on some islands select these fibers from the holes of the palm thief, which they need in their simple farming. Sometimes the palm thief is content with natural shelters - crevices in rocks, cavities in drained coral reefs, but even in such cases it uses plant material to line them, which retains high humidity in the housing.