Who knows the information about crabs Information about crabs Introduction to crabs

The habits of crabs.

The habits of crabs.

Naturally growing river crabs are generally burrowing or secluded. When the food is abundant and full, they often live in caves in order to avoid predators. When burrowing conditions are not available, they hide in gravel or grass.

River crabs usually prefer to live in rivers and lakes with clean water and abundant aquatic plants, and when they are in ponds, they often hide in the silt at the bottom of the pond. River crabs lie dormant at night, settle down when the bait is abundant and the environment is suitable, and once mature, they abandon their burrows and leave. River crabs grow in freshwater and reproduce in seawater.

After entering fresh water, crab seedlings generally live in rivers and lakes with abundant bait for about 18 months, and their gonads gradually mature. Mature river crabs begin to spawn in the offshore areas where sea and fresh water mix in late autumn and early winter, which is known as reproductive migration. Soon after mating, the female crab can lay eggs, which are attached to the female's abdominal limb hair in bunches and accumulate on the abdomen until hatchlings hatch.

This type of crab is called "egg-holding crab". River crabs can lay tens of thousands to millions of eggs at a time and can lay 2-3 times. In nature, fertilized eggs can only emerge after 4 months, and the hatching rate can reach about 90%.

The newly hatched larvae are small and shaped like daphnias, called flea-like larvae. The flea-like larvae have five molts and grow into crab seedlings (big-eyed larvae) in about 35 days, and the crab seedlings molt again to become larvae. The crab that has just shed its shell is called the soft shell crab, it is unable to feed and defend against the enemy, and the shell gradually hardens after 1-2 days, and then it gradually moves, and the crab body increases significantly after the shelling.

After the crab reproduces, its body quickly ages and dies. The feeding habits of the river crab are very mixed, it eats both meat and vegetables, and likes to eat fish, shrimp, snails, worms, earthworms, insects and their young and other animal foods, and also eats the same kind of injured or just molted shells, and the egg-holding crab also takes eggs as food when it is hungry. In the natural environment, most of the aquatic plants that river crabs can easily obtain are aquatic plants.

River crabs are very voracious, eat a lot of food, and have a strong digestive ability. When food is abundant, you can eat a lot, and when there is no food, you will not starve to death if you don't eat for a few days or even a month, because after eating, the excess nutrients will be stored in the liver, and the "soft shell crab" that has just been shelled is the nutrients stored in advance to maintain life. During the wintering period in the burrow, food intake is stopped or reduced.

River crabs are not only gluttonous, but also have a habit of grabbing and being aggressive. In order to compete for a good meal, they often kill each other.

1. Crabs (páng xiè) belong to the class molluscs, decapods, and are crustaceans, whose bodies are protected by hard shells and breathe by gills. Taxonomicly, it is related to shrimp, lobster, hermit crab.

It is a similar animal.

2. The vast majority of crabs live in the sea or near the sea, and some inhabit freshwater or land. Common crabs are pike crabs.

Offshore pike crab, blue crab and Chinese mitten crab.

River crabs, hairy crabs, clear water crabs), etc.

3. The body of the crab is divided into cephalothorax and abdomen. The back of the cephalothorax is covered with a cephalothorax, and the shape varies from species to species. The frontal part has a pair of antennae, and the outer side is a stalked compound eye.

The mouthparts include 1 pair of large jaws, 2 pairs of small jaws, and 3 pairs of jaw feet. There are 5 pairs of breasts and feet on both sides of the cephalothorax. The abdomen is vestigial, flattened, and zigzags on the ventral surface of the cephalothorax.

Males have a narrow and elongated abdomen, mostly triangular in shape.

Only the first two pairs of appendages are transformed into handicaps; The female has a broad abdomen, with 1 pair of double-branched appendages in each of the 2nd and 5th segments, densely covered with bristles, which are used to hold eggs. Most crabs are born in the sea, and the most common species are tropical shallow seas.

Funny crabs.

Crabs are mostly rampant, so they are called "rampant memories", which is unique among animal groups. The cephalothorax of the crab is flanked by five pairs of thoracopeds, except for the first pair of stinging feet, the remaining four pairs are strided. Since the joints of the foot can only move left and right, they have to rely on one side of the foot to advance sideways, and the other side of the foot to lie on the ground and walk sideways.

In addition, due to the long front and short back of several pairs of steps on the same side, when encountering obstacles, they can only turn around and bypass, and often climb in one direction along the obstacle one by one.

The intertidal zone and along the beach flat are the main places for crabs to inhabit, usually there are dozens of species to survive, and there are mainly fluffy near-square crabs, Chinese near-sea crabs and fiddler crabs along the beach flats in China. They prefer to hide under rocks or burrow in muddy sands, and their caves are all over the tidal flats, with 2 or 3 of them in an area of one square meter. Caves vary in depth, but each cave tends to have 2 openings.

Crabs hide deep in their burrows in winter.

Macrophthalmidae is a genus of macrophthalmus decapod arthropods.

The figure below is shownMacrophthalmus abbreviatus

<> are found in the area of Tokyo Bay in Japan, the waters near Incheon on the Korean Peninsula, the Shandong Peninsula, the Liaodong Peninsula and Guangdong Province in China.

The family Cancridae is a metacarcinus of the genus Metacarcinus decapod arthropods.

The picture below shows the Metacarcinus Magister (Cancer Magister) Dungenes Crab.

It is produced in Northern California, Oregon, Washington and other places in the United States.

Hairy crabs are Japanese mitten crabs, straight-fronted mitten crabs and narrow-jawed mitten crabs, and their main characteristics are dense foot hairs; The forehead is straight. with 4 sharp teeth; The width of the forehead is less than 1 m of the width of the carapace; The first antennae are transverse, the second antennae are erect; The length of the third foot segment is approximately equal to the width.

Menippidae is a genus of myomenippe decapod arthropods.

Pictured below is the Myomenippe Hardwickii

The stomach region of the carapace is subdivided into three regions. Its two anterolateral surfaces disintegrate into low-grained bulges. Each edge of the carapace is grainy, but finer near the surface edge.

The anterolateral margin is thin and rather acute. The front is almost a quarter of the maximum width of the carapace, and is separated from the track by a deep notch, and is Futaba. Legs are stout, hairy, or have a rough surface.