What is Coconut Crab?
Crabs, insects, spiders, and scorpions are all members of the phylum Arthropoda, which contains crabs, insects, spiders, and scorpions. Their "monstrous proportions" astounded even Charles Darwin. They're huge, and they're only found on islands in the Indian and southern Pacific oceans. They can weigh up to 9 pounds and have a leg length of 3 feet. Coconut crabs, commonly known as robber crabs because they steal food from unobservant campers, are not genuine crabs. They belong to the same family as hermit crabs, which are noted for dwelling in discarded mollusk shells. When coconut crabs are young, they do this, but as they get older, they stop. Let us learn more about the robber crabs.
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Coconut Crab: Taxonomic Classification
Distribution, Natural and Behavioural Traits of Robber Crab
Distribution and Habitat- Coconut crab populations are found only on islands in the Indian Ocean and the central Pacific Ocean, with the majority of sites being close to the shore. These incredibly gigantic crustaceans robber crabs live only on land and have no ability to swim until they reach maturity, despite being related to hermit crabs.
Physical Appearance- From leg tip to leg tip, adult coconut crabs are roughly 1 metre or 40 inches long and weigh about 4.5 kg or 10 pounds. The full-grown adult might be pale violet, brown, or deep purple in colour. The legs of young adults are tan with black stripes.
Anatomy- Coconut crabs are unable to swim and will drown if they come into contact with water. They breathe with a branchiostegal lung, which is a unique organ. This organ is a developmental step between the gills and the lungs, and it is one of the coconut crab's most important adaptations to its environment. The chambers of this respiratory organ are found in the cephalothorax's back end. They have tissue that is similar to that found in gills, but it is designed to absorb oxygen from air rather than water. They clean and moisten these breathing organs with seawater using their last, tiniest set of legs. Water is required for the organs to operate, which the crab delivers by brushing its wet legs over the spongy tissues surrounding it. The coconut crab possesses an additional set of rudimentary gills in addition to its respiratory mechanism. While these gills were most likely employed to breathe underwater during the evolution of the species, they no longer deliver enough oxygen, and an immersed coconut crab will drown in a matter of hours or minutes. The coconut crab's nose is another distinguishing feature. Depending on whether the smelled molecules are hydrophilic molecules in water or hydrophobic ones in air, the smelling process works very differently. Because most crabs dwell in water, they have specialised organs on their antennae called aesthetics that can detect both the concentration and direction of a smell.
Giant Coconut Crab Habitat and Growth- Coconut crabs can be found all throughout the Indo-Pacific, on remote coral atolls and tropical islands. They begin their lives in the ocean as minute larvae. They adapt to a totally terrestrial existence after about a month at sea, and they can no longer stay submerged underwater without drowning. Like the terrestrial hermit crabs from whence they evolved, they occupy empty snail shells as juveniles. Coconut crabs, on the other hand, recalcify their abdomens as they develop, and finally stop using shells since there aren't any large enough to accommodate them. Adults, on the other hand, dig out vast underground lairs. These burrows, which are commonly found beneath the roots of coconut trees and are lined extensively with coconut husks, provide a regulated environment for the crabs to live in throughout the day. Conspecifics are fiercely defended in their burrows. While insects and coconut crabs evolved along divergent evolutionary trajectories, their shared requirement to detect odours in the air resulted in the creation of very identical organs, demonstrating convergent evolution.
Diet- Coconut crabs are omnivorous, meaning they will eat both plants and animals. Birds have been killed, kittens have been eaten, and pig corpses have been ripped apart. Coconut crabs eat mostly fruit, such as coconuts and figs, in their diet. They will, however, eat almost everything organic, including leaves, rotten fruit, tortoise eggs, dead animals, and other animals' shells, which are thought to provide calcium. Live creatures that are too slow to flee, like newly hatched sea turtles, may also be eaten. One coconut crab caught and ate a Polynesian rat during a tagging experiment. Coconut crabs frequently try to steal food from one another and will pull their food into their burrows to keep themselves safe while eating. They've also been known to perform cannibalism, and they'll devour other coconut crabs without hesitation.
Breeding and Reproduction- In the months of May to September, especially in July and August, coconut crabs marry regularly and swiftly on dry land. The male and female battle, and the male mates by turning the female over on her back. It takes roughly 15 minutes to complete the mating process. The female then deposits her eggs on the bottom of her abdomen and glues them there for a few months, transporting the fertilised eggs underneath her body. The female coconut crab releases the eggs into the water at high tide at the time of hatching. The coconut crab eggs release normally in the months of October or November. The larvae are known as zoeas. All coconut crabs are said to do this on the same night, with a large number of females on the beach at the same time. The larvae float in the ocean for 28 days, during which time they are consumed by predators in enormous numbers. After that, they live as hermit crabs on the ocean floor and along the shore, sheltering in discarded shells for another 28 days. They go on dry land on occasion at such times. They change their shells as they develop, as do all hermit crabs. They leave the ocean permanently after these 28 days and lose their capacity to breathe in water. When young coconut crabs can't find a suitable seashell, they frequently use broken coconut bits. They acquire a tough abdomen when they outgrow even coconut shells. The giant robber crab grows and can reproduce 4 to 8 years after hatching. For a crab, this is an extremely extended period of development.
Human Use- The Giant Robber crab hunting is difficult due to their nocturnal nature and sharp claws. Coconut crabs are slaughtered and eaten as a delicacy on the many islands where they make their homes. Because of their enormous size, they produce a large amount of crab meat, and some local communities have come to rely on them as a food source or a source of revenue. Unsustainable hunting has, unfortunately, had a significant negative influence on Vulnerable species in several locations.
Threat- Introduced predators like rats, pigs, and ants like the yellow crazy ant pose a threat to the young coconut crab. Coconut crabs have no natural predators and are only eaten by humans. The adults have limited eyesight and rely on ground vibrations to identify enemies. Apart from other coconut crabs and humans, adult coconut crabs have no known predators. The coconut crab is heavily pursued due to its big size and high quality flesh, and it is extremely rare on islands with a human population. On different islands, the coconut crab is a delicacy and an aphrodisiac, and extensive hunting has jeopardised the species' survival in some locations. Overall, big human populations appear to have a negative impact on the coconut crab population, and populations are known to be dropping in some regions due to over-harvesting. In some locations, the coconut crab is protected, with minimum size requirements for harvesting and a breeding season.
Cultural Importance of Coconut Crab Around The World
It's ideal to go hunting on a moonless night with moist ground and flashlights. The three days following the new moon are ideal. Coconut crabs can be hunted during the day, but this requires either digging to reach them in their tunnels or lighting a fire to smoke them out of their hiding places. Coconut crabs are said to be attracted to charred coconut halves scattered on the ground. Kids in many parts of the world enjoy playing with coconut crabs by putting wet grass at an angle on a palm tree with a coconut crab. When the animal climbs down, it mistakenly believes the grass is the earth, so it lets go of the tree and falls. The coconut crab is prized for its power, and people are supposed to utilise it to protect their coconut plantations. If a coconut crab feels threatened, it may attack. In Tokyo, for example, the coconut crab is offered as a pet, especially if it is not fully developed. The cage must be robust enough to prevent the animal from escaping with its powerful claws.
Interesting and Mind Boggling Facts About Giant Robber Crab
The coconut crab holds the title of being the world's largest crab. They weigh over 5 pounds on average, although some can weigh up to 9 pounds, and have a 36-inch leg span.
Cracking a coconut takes a lot of effort, unless you're a coconut crab, of course. Their claws are capable of lifting things weighing up to 61 pounds, and their grasp is around ten times stronger than that of humans.
Adult giant robber crabs only exit their hiding places in quest of food or to mate.
Experts think that none other than famed biologist Charles Darwin was the first to describe these incredible creatures. After witnessing coconut crabs during his Beagle journey through the Indian Ocean, he wrote about them, characterising them as "monstrous in size" and marvelling at how easily the huge crab cracked through a hard-shelled coconut wrapped in husk.
They take refuge in abandoned snail shells and transport them as portable dwellings. Hatchling coconut crabs, like other crabs, begin their lives floating freely at sea. They find a snail shell and move in after about a month of eating and growing. As they begin to migrate to a land-based life, the small coconut crabs carry this mobile housing.
Other tropical fruits, fallen plant detritus, dead and decaying animals, rats, and other crab species may be found in the coconut crab's diet. They'll even devour people who aren't related to them.
These animals have a keen sense of smell that is both powerful and efficient. In fact, identifying scents takes up a significant chunk of their brain. Because coconut crabs live on land, their aesthetics look different from those of other crabs, resembling the smelling organs of insects known as sensilia.
Amelia Earhart's exact fate has never been discovered, however some say she was eaten by coconut crabs after crashing on an uninhabited island.
Robber crabs use their antennas in the same way that insects do to improve their reception. They have a keen sense of smell and are capable of detecting fascinating odours over long distances.
With its imposing size and strength, the hermit crab holds a special place in the islanders' tradition. The coconut crab is a delicacy and aphrodisiac among Pacific islanders, having a flavour that is similar to lobster and crabmeat. The eggs inside the female coconut crab and the fat in the belly are the most valuable portions.
FAQs on Coconut Crab
1. Is it Possible to Eat a Coconut Crab?
Answer. On different islands, the coconut crab is a delicacy and an aphrodisiac, and extensive hunting has jeopardised the species' survival in some locations. While the coconut crab is not dangerous by nature, its diet can make it so, and incidents of coconut crab poisoning have been reported.
2. Is it Possible For a Coconut Crab to Harm a Human?
Answer. Coconut crabs are hazardous because their pincers are among the most strong in the animal realm. They are, however, generally wary of humans and prefer to remain a safe distance from them. Attacks on humans are uncommon, but they, like most crabs, can become aggressive if they feel threatened.
3. Do Coconut Crabs Use Lungs Underwater?
Answer. Coconut crabs, like terrestrial crabs, have air-breathing organs that allow them to spend the majority of their lives out of the water. If they are submerged for long enough, the crabs will drown.
4. Do Coconut Crabs Steal For a Reason?
Answer. Coconut crabs frequently try to steal food from one another and will pull their food into their burrows to keep it safe while they eat. To eat coconuts or fruit, to escape the heat, or to avoid predators, the coconut crab climbs trees.
