Crabs are arthropod animals highly evolved. They are able to stay out of the water, which they need to breathe, for a long time. This is because they accumulate water inside, as if it were a closed circuit, changing it from time to time.
In this article on our site we talk about the types of crabs that exist in the world, beginning by explaining the main characteristics of the crabs. We will also show you a complete list with names and photographs so that you learn to recognize them. Keep reading!
Characteristics of crabs
The crabs are crustacean arthropods belonging to the infraorder Brachyura. Their body structure is highly specialized. If, normally, the body of arthropods is divided into head, thorax and abdomen, crabs have these three fused body parts Above all, the abdomen, which is very reduced and located under the shell.
Crab shells are very broad, often being wider than long, giving them a very flattened appearance. They have five pairs of legs or appendages. The first pair of appendages, known as chelicerae, are overgrown in males of many species.
They can crawl forward slowly, but generally move sideways, especially when crawling quickly. Most crabs cannot swim, although in some species the last pair of legs ends in a kind of broad, flattened paddle or oar, which gives them allows some swimming locomotion.
Crabs breathe through gills Water enters the base of the first pair of pasta, circulates through the gill chamber, and exits in an area near the eye. The circulatory system of crabs is open. This means that sometimes the blood travels through veins and arteries and, at other times, it is poured into the interior of the body. They present a heart that can have variable shapes, with ostioles, which are holes through which blood enters the heart from the body, and then travels through blood vessels.
Crabs are omnivorous animals. They can feed on algae, fish, molluscs, carrion, bacteria and many other organisms. On the other hand, they are oviparous animals, they reproduce through eggsFrom these eggs come larvae that will undergo different stages of metamorphosis until they reach the adult state.
How many kinds of crabs are there in the world?
In the world there are about 4,500 types of crabs or species These animals usually live in intertidal zones, such as the shores of beaches, estuaries and mangroves. Others live in somewhat deeper waters, and some species even inhabit places as inhospitable as oceanic hydrothermal vents, which reach temperatures of up to 400 ºC.
Some of the most well-known types of crabs are:
1. Fiddler Crab
The fiddler crab (Uca pugnax) inhabits many coastal marshes along the coasts of the Atlantic Ocean. They are burrow builders that they use to shelter from predators, breed, and hibernate during the winters. They are small-sized crabs, about 3 centimeters across the largest individuals.
They have sexual dimorphism, being the most dark green with a blue area in the center of the shell. Females do not have that spot. Males can also present a chelicerae with overgrowth and, in some cases, both. During courtship, males move their chelicerae in such a way that they appear to be playing a violin.
two. Christmas Island Red Crab
The red crab (Gecarcoidea natalis) is endemic to Christmas Island, Australia They live solitary inside the jungle, spending the dry months buried in the ground, hibernating. When the rainy season begins, during the fall, these animals perform a spectacular mass migration to the sea, where they mate.
Red crab pups are born in the ocean, where they spend a month undergoing various metamorphoses in order to live on land.
3. Japanese Giant Crab
The Japanese giant crab (Macrocheira kaempferi) lives in the depths of the Pacific Ocean off the coast of Japan. They are colonial animals, so they live in very large groups It is the largest living arthropod that exists. Their legs can measure more than two meters in length and can reach 20 kilograms of weight.
Something very curious about these animals is that they adhere to their body remains that they find around them to camouflage themselves. If they change their environment, they change their remains. For this reason, they are also known as "decorative crabs".
4. Common crayfish
The common crayfish (Carcinus maenas) is native to the west coast of Europe and Iceland. Although it inhabits other parts of the planet as an invasive species, for example, South Africa or Central America. They can have various shades, but above all they are greenish They do not reach sexual maturity until they are 2 years old, when they reach a size of 5 centimeters However, its longevity is 5 years in males and 3 in females.
5. Atlantic Blue Crab
The Atlantic blue crab (Callinectes sapidus) is named for the blue color of its legs, but its shell is a greenish hue. The claws of their chelicerae are red. They are invasive animals in many parts of the world, although they are originally from the Atlantic Ocean. They can live in waters with very different conditions, fresh or s alt water, and even polluted water.
More examples of crabs
Here is a list of other types of crabs:
- Patagonian crab (Lithodes santolla)
- Moorish crab (Menippe mercenaria)
- Black crab (Gecarcinus ruricula)
- Red land crab (Gecarcinus lateralis)
- Pygmy Crab (Trichodactylus borellianus)
- Swamp Crab (Pachygrapsus transversus)
- Hairy Crab (Peltarion spinosulum)
- Rock Crab (Pachygrapsus marmoratus)
- Granular crab (Neohelice granulata)
- Blue Crab (Cardisoma crassum)
