What are the habits of river crabs, and the living habits of crabs

Crabs like to inhabit the mud banks and mudflats of rivers, lakes and rice paddies, and they also like to hide in rocks and aquatic plants.

1) Cavemen. Crabs prefer to live in the mud banks of rivers and lakes or in burrows in tidal flats, or hide in rocks and aquatic grasses. In rivers where the tide rises, most of them are located between high and low water levels, while river crabs living in lakes and reservoirs have scattered burrows and are mostly below the water surface, so they are not easy to find.

2) Eating habits. Crabs have a very mixed diet, mainly eat aquatic weeds and humus under natural conditions, eat animal carcasses, and also like to eat snails, mussels, worms, insects, and occasionally prey on small fish and shrimp. Because crabs have a strong ability to endure hunger, they generally do not eat for ten days and half a month without hunger to death. But in June to September it grows vigorously and has a large amount of food.

In other months, they are often semi-starved. During the overwintering period, they rarely eat.

3) Molting and growth of crabs.

The growth process of crabs is accompanied by larval molting, juvenile crabs or adult snails, and the larvae change their shape every time they molt, which is divided into one stage. The molting process needs to absorb a large amount of water, so the mass increases significantly in the molting process, but in the subsequent growth, the loss of water is slow, and gradually replaced by tissue growth, the growth rate of crabs is restricted by environmental conditions, especially water temperature and bait.

Crabs mostly inhabit the rocks of mountain streams, and a few crabs can adapt to life on land, burrowing in damp mud holes, and migrating to the sea during the breeding period. The vast majority of crabs are omnivorous. Some crabs are carnivorous, such as pike crabs, which can prey on fish, shrimp and molluscs.

Crabs scrape or filter feed on algae and organic detritus.

Crabs belong to the class Mollusk, Decapod, and are crustaceans whose bodies are protected by a hard shell and breathe by gills. Taxonomicly, it is the same animal as shrimp, lobster, and hermit crab. The vast majority of species of crabs live in the sea or near the sea, but some inhabit freshwater or land.

Common crabs include pike crab, open sea pike crab, blue crab and Chinese mitten crab (river crab, hairy crab, clear water crab) and so on.

螃crab (pángxiè): animal kingdom, phylum Arthropods, Crustacea, Decapod, reptile suborder. Crabs are crustaceans whose bodies are protected by hard shells.

Crabs breathe by gills. In terms of taxonomy, crabs are classified as the same animals as shrimps, lobsters, and hermit crabs. The vast majority of crab species live in or near the ocean, while some live in freshwater or on land.

They rely on the mother crab to give birth to baby crabs, and each time the mother crab lays a large number of eggs, the number of which can reach more than millions. Crabs rely on the geomagnetic field to determine direction. The history of crab eating in China has a long history, which is recorded in "Yi Zhou Shu, Wuhui Solution" and "Zhou Li, Tianguan, and Blister".

The film named after the crab was released in Venezuela in 1982.

Habits. After several shells, they grow into big-eyed larvae, and the big-eyed larvae grow into juvenile crabs after several shelling, and the appearance of juvenile crabs is almost the same as that of adult crabs, and then after several shells, they become crabs. Most marine crabs are released into the ocean without hatching after their eggs have matured. The hard carapace of the crab protects the crab from predators, but the carapace does not expand as the body grows.

Therefore, the growth of crabs is interstitial, that is, after a period of time, the body will continue to grow after the old shell is molted. The largest crabs on the planet are spider crabs, with their feet spread out and wide to a meter, and the smallest crabs are bean crabs, which are less than half a centimeter in diameter. Although the crab is small, it has all kinds of organs.

When the hard shell of the crab is removed, we can find that the crab's body parts are protected by a layer of shells, these shield-like shells, which biologists call carapace. The pair of appendages in front of them have strong chelae that can be used for foraging, and the other four pairs of appendages are the feet of the crabs, and the crabs rely on these four pairs of appendages to walk and move, and they walk in a unique and interesting way, mostly walking sideways rather than straight forward. The exception is monk crabs, which walk straight.

Crabs spend most of their time looking for food, they are not picky eaters, and they can eat as much food as they can get their hands on. Small fish and shrimp are their favorite, and some crabs also eat seaweed, even animal carcasses or plants.

Crabs eat other animals, and other animals may also eat crabs, for example, humans use crabs as a delicacy. There are also waterfowl that eat crabs!Some fish also like humans to eat crab legs.

When young and juvenile crabs float in the sea in groups, they may be eaten by other marine organisms, which is why crabs lay a lot of eggs when they lay eggs.

Fiddler crabs are common crabs on the seashore, and the giant claws of male fiddler crabs resemble playing a violin, so they are also called fiddler crabs or fiddler crabs.

Territorial: Aggressive in eating at night.

River crabs belong to the phylum Arthropods, Crustaceans, Decapods, Reptiles, Brachytails, Square Crabs, Bowleggys, and Mitten Crabs. There are four species of mitten crabs in China, namely Chinese mitten crab, Japanese mitten crab, narrow-fronted mitten crab and straight-fronted mitten crab (Figure 2-1). Narrow-fronted mitish crab and straight-fronted mitten crab are not only small in individuality, but also small in yield, and have no economic value. Chinese mitten crab and Japanese mitten crab are usually called river crabs, hairy crabs, crabs, clear water crabs and hairy crabs, etc., which are large, good meat quality and high yield.

The main differences between them are:

Figure 2-1 Morphological comparison of four species of mitten crabs.

1) Chinese mitten crab.

The cephalothorax is distinctly raised, the frontal margin has 4 sharp teeth, the gap between the teeth is deep, the middle one is the deepest, there are 6 wart-like protrusions behind the frontal horn, the anterior lateral margin has 4 teeth, the 4th side teeth are small and distinct, and the toe nodes of the last pair of feet are pointed and claw-like.

2) Japanese mitten crab.

The cephalothorax is not distinctly raised, the frontal margin has 4 sharp teeth, but the middle two teeth are round and blunt, the outer two teeth are sharper, the interdental gap is shallow, the middle one is the shallower, there are 4 wart-like protrusions behind the frontal horn, the anterior lateral margin has 3 teeth, the 4th lateral tooth is vestigial, and the toe segment of the last 1 pair of feet is broad and flattened.

Chinese mitten crab is distributed in the coastal provinces of the Bohai Sea, the Yellow Sea and the East China Sea in China, and it has two populations, among which, the northern population is represented by the Liaohe (Yellow River) water system crab, and the southern population is represented by the Yangtze River (Oujiang River) water system. Japanese mitten crab is mainly distributed in Guangdong, Guangxi, Fujian, China's Taiwan coast, Japan coast, Russian Far East, it is also divided into two populations, among them, the northern population is represented by the Suifen River system (locally known as "Russian crab"), and the southern population is represented by the Nanliujiang River system (commonly known as "Hepu crab").

The results showed that after the transplantation of the crab to the Yangtze River system, it was not adapted to the growth environment of the middle and lower reaches of the Yangtze River, and the commercial crab matured one month earlier (late August), and its molting times were small, and the individual was small and the quality was poor. What's more serious is that the Liaohe River system Chinese mitten crab and Japanese mitten crab are mixed, unfortunately, China's "big crab farming" in the past ten years, the crab seedlings and crab species of different water systems or different populations are transplanted to other places for breeding, resulting in the mixing of river crab germplasm resources in various water systems, and the loss of its intangible assets is immeasurable.

Therefore, it is strictly forbidden to transplant river crabs from different water systems to other water systems for breeding.

River crab is also called Chinese mitten crab, Panjin river crab and Yangcheng Lake miscellaneous crab all belong to Chinese mitten crab, because of the different places of breeding, for example: wild river crab is not artificially cultivated, rice field river crab is artificially bred in the rice field, river crab is bred by the river, reed pond crab is grown in reed pond, and the different tastes of river crabs are different. Friends who like to eat river crabs suggest that the next Panjin river crab is really delicious, much more delicious than hairy crabs.