【Smart Farmer】Illustrated Book｜Have you eaten crabs today?

Crabs are delicious and fun aquatic creatures. They form a large family in the aquatic animal world. There are about 4,500 species of crabs in the world, and nearly 800 species in China. With so many crabs, I will first list the interesting ones.

According to the growth environment of crabs, they can be divided into sea crabs, river crabs, lake crabs and stream crabs. According to their uses, there are common edible crabs, ornamental crabs and many undeveloped crabs. Their footprints are all over the world. They enjoy themselves and survive on their own. They are part of the biodiversity in this colorful world.

Most crabs live in the sea, and the most crabs live in tropical shallow seas, such as the frog crab family, the steamed crab family, the jade crab family, the swimming crab family, and the fan crab family. They mainly live in the coastal area; the square crab family and the sand crab family live in the vast intertidal zone. Some are relatively rare, such as the drifter crab and the bow-leg crab, which can live attached to wood or other floating objects. There are also many crabs that live in symbiosis with other animals, such as the cotton crab family and the Guan Gong crab family. What is more interesting is that many crabs, such as the bean crabs, often dive into the mantle cavity of some mollusks, or live in symbiosis in the pipes of polychaetes. The saddest are the coral crabs, which live in the capsules formed by reef-building corals. After mating, the adult female crabs are imprisoned in the capsules for life, and the hatched larvae can escape through the unclosed small holes.

In addition to these saltwater crabs, there are some crabs that live in brackish water, that is, where the sea and rivers meet, such as blue crabs, and some crabs grow and reproduce entirely in fresh water, either in lakes, rivers or mountain streams.

Below are some common edible crabs.

Saltwater crabs. The representative of saltwater crabs is the swimming crab. The Chinese name of the swimming crab means that they look like the shuttle used in ancient weaving, and they shuttle through the water as fast as the shuttle. In English, it is called swimming crab, which means a crab that can swim.

There are many types of swimming crabs. The most common one is the deep-sea swimming crab. Their most obvious feature is the white and mottled pattern on their bodies. The female crabs are light in color, while the male crabs are dark in color.

Pelagic swimming crab (male), provided by the author

Deep-sea swimming crab (female), picture from "Atlas of Chinese Marine Life"

Swimming crab, provided by the author

Swimming crab, provided by the author

Sword-wielding swimming crab, provided by the author

In the swimming crab family, there are some that are not called swimming crabs, but crabs, which live near the coast.

Warrior crab, picture from "Economic shrimps and crabs in the East China Sea"

Sagami crab, picture from "Atlas of Chinese Marine Life"

Another species of the swimming crab family is the mud crab (scientific name: Scylla serrata), because it is a little fat, unlike the swimming crab. The mud crab likes to live in the muddy bottom of the shallow sea near the coast and the estuary where the sea and fresh water meet. It is ferocious and fish, shrimp and shellfish are its delicacies. Therefore, the meat of the mud crab is delicious, nutritious, and has the effect of nourishing and strengthening the body. Especially for female crabs that are about to get pregnant, red or yellow paste will be produced in their bodies. This kind of crab is called "paste crab" in southern China and is known as "sea ginseng". It is found in coastal areas of Zhejiang, Guangdong, Guangxi, Fujian and Taiwan in my country, especially in the Jiangsu and Zhejiang areas.

Scylla serrata, provided by the author

There are of course more types of edible sea crabs than these, these are just the common varieties on the market. At present, aquatic technology personnel have overcome the difficulties of artificial breeding of most sea crabs, providing us with insurance for enjoying delicious sea crabs in daily life.

Freshwater crabs. Freshwater crabs include crabs in rivers, lakes, and streams. There is a representative freshwater crab called the Chinese mitten crab (Eriocheir sinensis H.Milne-Edwards). Its claws are very large, which are used for feeding and fighting enemies. The inner and outer edges of the palms are densely covered with velvet, hence the name mitten crab. It is also called river crab, hairy crab, clear water crab, and hairy crab. It can be found in almost all rivers, lakes, and streams. In recent years, hairy crabs are one of the main varieties of rice field integrated breeding by Chinese aquatic scientists. In many places, rice has also formed some crab-rice brand products due to the ecological model of combining crab breeding. Hairy crabs are a long-standing delicacy in my country.

Chinese mitten crab, provided by the author

Freshwater crabs are mainly distributed in tropical areas and extend to subtropical and temperate marginal areas. Most freshwater crabs live under rocks in mountain streams or among waterweeds and muddy sands on both sides of stream banks. Some also live in caves on the banks of rivers, lakes, and ditches. They do not stay submerged in water for long periods of time, but live a semi-terrestrial life near water or in humid places. Freshwater crabs do not have velvet claws like mitten crabs, but their colors are prettier.

Interestingly, crabs are like Peking Opera in the sea, with all the roles of Sheng, Dan, Jing, Mo and Chou. For example, the domineering king crab is named for its huge size, with a maximum weight of 10 kilograms. King crabs grow slowly and can live up to 30 years. Most crabs move horizontally, but king crabs can also move vertically.

King crab, provided by the author

The gentle imperial concubine crab is also called tiger crab. It makes people wonder whether it is gentle or fierce. Perhaps it is named because its face is plump, a bit like an imperial concubine.

Royal crab, provided by the author

The small Guan Gong crab looks like the Guan Gong mask in Chinese classical drama. The Guan Gong crab family is a group of Guan Gong crabs that are widely distributed in the world's oceans. However, the poor Guan Gong crab is only edible because of its small size. Although it is edible, it is mainly used as poultry feed. Young Guan Gong crabs are a natural delicacy for fish.

Guan Gong crab, picture from "Economic Shrimp and Crabs in the East China Sea"

There are also the shining blue monk crabs. Short-fingered monk crabs are also called soldier crabs, sea pearls or sea monks. Do their crab shells look too much like the monks' heads that have been shaved and shone with a shining blue light? As the crab generals guarding the Dragon Palace, the monk crabs are too small, weighing only 2 grams on average. However, the small monk crabs can also walk in a unique way. Unlike other crabs, they can walk forward with a majestic and proud manner.

Monk crab, picture from "Atlas of Chinese Marine Life"

There are also some crabs whose names are too consistent with their appearance. For example, the bread crab looks like freshly baked bread; the red crab of Christmas Island has a Santa Claus face, with all the facial features and wearing Santa Claus's red robe. There are many other pictographic crabs, such as the one that looks like pine leaves is called pine leaf crab, the one that looks like snow covered with goose feathers is called snowman crab, the one that looks like a small bean is called bean crab, and so on.

Brown crab, provided by the author

Chinese bean crab, picture from the Atlas of Chinese Marine Life

Author: Liu Yadan (National Chief Science Communication Expert, former Assistant Secretary-General of the Chinese Society of Fisheries, Assistant Secretary-General of the China Rural Professional and Technical Association)

Audit expert: Dai Guoqing (Secretary-General of China Algae Industry Association)

Editor: Wu Yuetong

Proofreader: Jiang Ruiyi (internship)