Facts about Crabs, "Scientific name for Crab is Brachyura". A "Crab" is a decapod crustacean that belongs to the Brachyura infraorder, which normally have an extremely small projecting abdomen, and is generally hidden under the thorax completely. It is a fact that Crabs live in all the oceans of the world, including on land and in fresh water. The Crabs are usually covered with a chunky exoskeleton and they have only one pair of claws. Several other creatures with analogous names, such as king Crabs, hermit crabs, porcelain crabs, crab lice and horseshoe crabs, are not exact Crabs.
Generally, the thicker exoskeleton of crabs is primarily made up of calcium carbonate, and it is armed with only one pair of claws or chelae. Though the Crab lives in all oceans of the world, they usually prefer to live in tropical areas. They differ in size, according to their variety. A typical pea crab has a few millimeters sizes, whereas the Japanese spider crab can have a maximum leg span of 13 feet (4 meters).
Approximately, 850 crab varieties live in freshwater, and some may be earthly or semi-earthly species, as well. Previously, crabs were considered a monophyletic group, but now they are considered to represent at a minimum of two separate lineages, one in the New World and another in the Old World.
Habitually, Crabs show noticeable sexual dimorphism. Male Crabs habitually have bigger claws, a propensity, which is chiefly distinct in the fiddler Crabs of the Uca genus of the Ocypodidae family. In fiddler Crabs, male crabs have a single claw that is deeply enlarged and it is exercised for communication, chiefly for magnetizing a mate. Another conspicuous dimorphism is the shape of the abdomen. In the majority of male Crabs, the abdomen is narrow and in the form of a triangular, whereas female Crabs have a wider, rounded abdomen. This is attributable to the fact that females use to breed the fertilized eggs on their pleopods.
Crabs are omnivorous creatures, and they feed mostly on algae. The Crab also feeds on worms, mollusks, other crustaceans, bacteria, fungi and detritus, according to their availability.
Usually, Crabs walk sideways, due to the articulation of their legs that creates a sidelong walk more competent. However, a few Crabs, such as Libinia emarginata, Raninids and Mictyris platycheles walk backwards or forwards. A few crabs, particularly the Matutidae and Portunidae are also competent to swim, so as their end pair of walking legs is compressed into swimming paddles.
Usually, Crabs are vigorous animals with multifaceted behavior patterns. They can correspond by waving or drumming their pincers. Crabs are inclined to be violent towards each other and habitually, the male Crabs fight to get access to female Crabs. On rock-strewn seashores, where most caves and gaps are engaged, Crabs may as well, brawl over hiding holes. Fiddler crabs excavate burrows in mud or sand, which they utilize for hiding, resting, mating and to protect them against intruders.
Crabs draw a mate through visual, chemical, vibratory or acoustic means. Pheromones are employed by nearly all fully sea Crabs, whereas earthly and semi-earthly crabs frequently use visual gestures. The huge amounts of brachyuran Crabs contain internal fertilization and they use to mate between their bellies. For many marine Crabs, mating occurs after the female Crab molted and is still flexible. Female Crabs can stock up the sperm for a longer period prior to employing it to fertilize their eggs. When fertilization occurs, the eggs are free onto the abdomen of the female Crab, beneath their tail flap, protected with a sticky substance. In this place, they are secluded during embryonic growth. Female Crabs, carrying eggs are known as berried because the eggs look like round berries.
The average lifespan of the Crab ranges from 1 year to 13 years, according to their varieties.