Shrimp has a slender body.
Shrimp has a slender body, most of which are between18 ~ 23 cm long, and the largest one is 26 cm long and weighs 60 ~ 80 g. There are also extra-large individuals. It is reported that 1 August, 1996, a fisherman in Guangxi caught three super-large prawns in Beibu Gulf, weighing * * * 1.42 kg, the largest one weighing 0.49 kg, the shrimp being 49 cm long, and its whiskers being nearly1m. Shrimp's body is divided into head, chest and abdomen. The head has two pairs of red long whiskers, called tentacles, which are 2.5 times longer than its body. They extend to the rear along both sides of its body, making it look dashing. In ancient times, it was called bearded male, tiger head male and curvy boy. There are a pair of black eyes on the long eye stalk, which can make it see six ways when it rotates with the eye stalk. It has 10 pairs of appendages, so it is called decapod, 5 pairs are used for catching food and crawling on the seabed, and 5 pairs are used for swimming. The tail is a flat tail fan.
The life of prawns is very short.
Shrimp is a big individual. In the past, it was priced according to sales and the catch was calculated according to pairs. Over time, shrimp became its name. Li Shizhen's Compendium of Materia Medica in the Ming Dynasty said: "There are five-color shrimps in Fujian, which are also more than a foot long. They work in pairs and are called prawns." People put the word "China" in front of "prawn", which is called China prawn, also known as Oriental prawn.
Shrimp is mainly distributed in the Yellow Sea and Bohai Sea. It usually lives on the seabed, likes to move on the seabed of sediment, and catches larvae or diatoms of small crustaceans for food. Nereis and Serpentis are also the favorite foods for shrimp. The Yellow Sea and Bohai Sea not only provide abundant food sources for prawns, but also provide suitable environmental conditions, which are very suitable for the growth, development and reproduction of prawns.
Every year, prawns spend a cold winter in the south of the Yellow Sea. When the spring breeze sends the message of spring, since March, prawns have flocked to the north for reproductive migration in batches. Shrimp likes to lay eggs near the estuary, and the coast of Bohai Sea is a good place for its reproduction and development. Therefore, a large group of prawns in the north, bypassing Shandong Gaojiao, swam to Bohai Bay and Liaodong Bay in early May after a long journey to Qian Qian Rice. In early May, regardless of the fatigue of the journey, the female shrimp spread her full hopes to the sea and laid hundreds of thousands, millions or even tens of millions of eggs. Shrimp eggs are very small, and 400 eggs are arranged together to be 1 cm long. The life of prawns is very short. After spawning, the parent prawns will die before they see their children to be born, leaving a broad living space for future generations.
Shrimp eggs develop into larvae. It is very small, only1/3mm long. It looks strange, and there is almost no similarity between it and adult shrimp. It takes a complicated metamorphosis process to grow into a shrimp. The early juvenile shrimp is called nauplius larva, and it must shed its skin once every time it lives. Every time it sheds its skin, its body grows bigger and its appearance changes. After molting for six times, it develops into a flea-like larva, then into a mysid larva, and after molting for three times, it grows into a larva of only about 6 mm. At this time, they are very gluttonous and grow fast, and they are similar to adult shrimps in only half a year. Of course, from hatching to growing into a shrimp, the road is long and bumpy, many members died, some served as a good meal for other animals, some were frustrated and died in the process of metamorphosis and molting, and only some members survived the disasters again and again and became the lucky ones. After several months of feeding and growth changes, the young shrimp all entered adulthood from childhood at the end of autumn, their bodies grew up and their sexuality matured, so they were busy looking for mates and mating.
prawn
Mature female shrimps often release a chemical substance to inform male shrimps of their physiological status and attract male shrimps. Male shrimps will follow immediately after they get the information. Once the two sides hit it off, the male shrimp waited patiently. Female shrimps should shed their skin and put on new clothes before mating. Once the molting process is completed, before the new skin becomes hard, the male shrimp immediately hugs the belly of the female shrimp, and the sperm pod containing sperm is smoothly delivered to the female shrimp's delivery device. The female shrimp keeps the sperm in the seminal vesicle of the chest, and when she comes back to lay eggs next spring, she releases the sperm while laying eggs to fertilize the eggs. Shrimp is very strange. Instead of laying eggs and discharging sperm synchronously in the reproductive season, males and females mate first, and the sperm remains in the female shrimp for several months.
Winter is coming, and the north wind brings the chill of the north. The weather is getting cold and the sea water is getting cold. Unable to bear the cold, prawns started their wintering migration to the south, that is, to the deeper waters in the southern Yellow Sea, along the path taken by their ancestors in droves, where they spent the cold winter. It is also a good opportunity to catch prawns twice in the process of going south in winter and going north in spring every year.
Of course, not all shrimps lay their eggs in the sea just like China prawns. Some shrimps hatch their eggs in egg bags; After laying eggs, the female shrimp collects the eggs and sticks them into chunks the size of walnuts. She holds the chunks with her front feet to hatch, and keeps turning them to keep them clean. For several weeks, the female shrimps didn't eat or drink, starved, and patiently watched the shrimps being born with expectant eyes. There are more than 50 species of prawns in China's coastal areas. Besides China prawns, there are also slightly smaller new prawns, Penaeus monodon and Penaeus breviscapus with brown transverse spots, and Penaeus penicillatus distributed in Guangdong, Fujian and other places. There are many prawns in the world with great economic value, such as the annual output of polychaete distributed along the Atlantic coast of North America reaching100000 tons, and the leading prawns in India, the three-ditch prawns in France and the Japanese prawns are all important economic prawns. 1989 The total output of shrimp in the world was 2.2 million tons, of which cultured shrimp accounted for 26%, while new shrimp accounted for15% of the total output of cultured shrimp.