The Japanese spider crab can look quite ominous with its massive body of 16 in (40 cm) and huge Japanese spider crab legs 12.1 ft (3.7 m).

But this appearance can be deceiving. This orange arthropod with white spots is on the contrary a docile creature of the oceans.

It is known to be a nocturnal being that mostly survives on the remains of other dead animals.

This reduces its requirement to predate and renders its generous size only to defend itself. On average, these giant spider crabs can weigh about 35.24-44.05 lb (16-20 kg).

Japanese spider crabs are known to be the largest arthropods on the planet due to the giant Japanese spider crab size.

They measure a whopping 12.1 ft (3.7 m) from one claw to the other and their body is of about 16 in (40 cm).

Their massive legs and comparatively smaller body gives them the appearance of a spider from which they derive their name.

The Japanese spider crab size comparison between sexes is worth noting.

The males are known to have longer front legs than those of the females. The bodies of the female on the other hand are wider as compared to the males.

Being the biggest arthropod, the Japanese Spider Crab weighs an overwhelming 35.24-44.05 lb (16-20 kg). Their mass is mostly concentrated on their body as their legs are leaner.

Japanese spider crabs are mostly scavengers. The Japanese spider crab diet mostly consists of the dead and decaying remains of other aquatic animals.

They are also omnivorous and like to eat algae, plants, and small fishes as well. Their dietary habit makes them less threatening as compared to other marine creatures.

These crabs don’t eat humans and cannot kill humans but they can cause injury with their claws.

They are not dangerous provided you don’t provoke them. They are scavengers and can go for days without food.

These giant spider crabs reside at a depth of about 492-984 ft (150 – 300 m) on the rocky and sandy continental shelf of the Japanese Pacific Ocean.

But under some circumstances, they have also been seen to reside in shallower waters at a depth of about 1969 ft (600 m).

Then again these crabs travel to the shallower waters of the continental shelf during the spawning season and as a result, there is a higher density of its younger population in this range.

This giant spider crab species is known to mate during the spring (January to March).

During this time, they travel to the shallower waters in their habitat.

The male crabs which have a store of sperms in their spermatoph

They do this with the help of their first two chelipeds (the pair of long legs that have the pincer like claws).

Unlike other marine animals, the process of fertilization is internal in the Japanese spider crabs, taking place within the female’s body.

The female crab then carries the fertilized eggs in her abdominal appendages.

These females are known to lay about 1.5 million eggs per season but much fewer than this actually hatch.

This process of hatching takes place after about 10 days of laying the eggs.

After hatching, the baby crabs do not have any feet and undergo multiple shedding phases. It is only after the natural Japanese spider crab molting that their gigantic limbs are formed.

Various researchers have seen that the Japanese spider crab’s lifespan is about 100 years.

But due to incessant fishing, the life span of these giant spider crabs can be drastically reduced.

Japanese spider crab predators include larger marine creatures such as octopuses and stingrays.

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